U.S. patent application number 10/788995 was filed with the patent office on 2004-09-02 for catalytic processes for the controlled polymerization of free radically (co)polymerizable monomers and functional polymeric systems prepared thereby.
This patent application is currently assigned to Carnegie Mellon University (a non-profit Pennsylvania organization). Invention is credited to Gaynor, Scott G., Matyjaszewski, Krzysztof, Miller, Peter J., Paik, Hyun-jong, Pintauer, Tomislav, Pyun, Jeff, Qiu, Jian, Teodorescu, Mircea, Xia, Jianhui, Zhang, Xuan.
Application Number | 20040171779 10/788995 |
Document ID | / |
Family ID | 26823972 |
Filed Date | 2004-09-02 |
United States Patent
Application |
20040171779 |
Kind Code |
A1 |
Matyjaszewski, Krzysztof ;
et al. |
September 2, 2004 |
Catalytic processes for the controlled polymerization of free
radically (Co)polymerizable monomers and functional polymeric
systems prepared thereby
Abstract
Further improvements have been made in processes for controlled
polymerization of free radically (co)polymerizable monomers
mediated by a transition metal complex participating in a redox
reaction which involves transfer of a radically transferable atom
or group to and from an initiator or dormant polymer and the
growing active polymer chain ends. Two improvements involve the
choice of counterion in the transition metal complex. In one
improvement the transition metal is held in close conjunction with
a solid support through interaction with a counterion directly
attached to the support. This cognition also allows for
improvements in catalyst utilization including catalyst recovery
and recycle. In another improvement, particularly suitable for
controlled polymerization of certain monomers with an expanded
range of transition metals, the function of counterion and ligand
in the development of the transition metal based catalyst is
superseded by use of salt containing a soluble organic counterion.
These and other process improvements have been employed to prepare
an extended range of novel polymeric materials and novel processes
for the preparation of functional polymers including a novel
catalytic Atom Transfer Coupling Reaction.
Inventors: |
Matyjaszewski, Krzysztof;
(Pittsburgh, PA) ; Gaynor, Scott G.; (Pittsburgh,
PA) ; Paik, Hyun-jong; (Pittsburgh, PA) ;
Pintauer, Tomislav; (Pittsburgh, PA) ; Pyun,
Jeff; (Pittsburgh, PA) ; Qiu, Jian;
(Pittsburgh, PA) ; Teodorescu, Mircea; (Bucharest,
RO) ; Xia, Jianhui; (Pittsburgh, PA) ; Zhang,
Xuan; (Woburn, MA) ; Miller, Peter J.;
(Imperial, PA) |
Correspondence
Address: |
KIRKPATRICK & LOCKHART LLP
535 SMITHFIELD STREET
PITTSBURGH
PA
15222
US
|
Assignee: |
Carnegie Mellon University (a
non-profit Pennsylvania organization)
Pittsburgh
PA
|
Family ID: |
26823972 |
Appl. No.: |
10/788995 |
Filed: |
February 27, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10788995 |
Feb 27, 2004 |
|
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09534827 |
Mar 23, 2000 |
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60125809 |
Mar 23, 1999 |
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60142980 |
Jul 12, 1999 |
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Current U.S.
Class: |
526/303.1 ;
525/244; 526/171; 526/300; 526/319; 526/330; 526/346 |
Current CPC
Class: |
C08F 293/005 20130101;
Y02P 20/584 20151101; C08F 2/38 20130101; Y02E 60/13 20130101; H01G
11/30 20130101; C08F 293/00 20130101; C08F 2438/01 20130101 |
Class at
Publication: |
526/303.1 ;
526/300; 526/319; 525/244; 526/330; 526/171; 526/346 |
International
Class: |
C08F 004/80 |
Goverment Interests
[0002] Portions of this application relating to hybrid polymers
were funded in part by the National Science Foundation. Portions of
this application relating to emulsions were funded in part by the
Environmental Protection Agency. The United States Government may
have rights in this application.
Claims
1. A controlled polymerization process, comprising: polymerizing
free radically (co)polymerizable monomers in the presence of a
system initially comprising: an initiator having a radically
transferable atom or group; and a catalyst which participates in a
reversible cycle with at least one of the initiator and a compound
having a radically transferable atom or group; and forming a
(co)polymer.
2. The process of claim 1, wherein the initiator contains a second
fuictional group.
3. The process of claim 2, wherein the second functional group
comprises a polar substituent.
4. The process of claim 3, wherein the polar substituent is a
carboxylic acid group.
5. The process of claim 1, wherein the free radically
(co)polymerizable monomers are chosen from a group consisting
acrylates, (meth)acrylates and (meth)acrylamides.
6. The process of claim 1, further comprising: preparing the
initiator having a radically transferable atom or group by
decomposing a first standard free radical initiator to a radical in
the presence of a transition metal salt in a higher oxidation
state, the transition metal salt comprising: a radically
transferable counterion, wherein the transition metal salt
transfers the radically transferable counterion to the radical of
the first initiator to form the initiator and the transition metal
salt in a lower oxidation state.
7. The process of claim 6, wherein the catalyst is the transition
metal salt in the lower oxidation state.
8. The process of claim 7, wherein the transition metal comprises a
complex counterion.
9. The process of claim 8, wherein the complex counterion is an
onium based counterion.
10. The process of claim 1, wherein the catalyst comprises a
transition metal salt.
11. The process of claim 10, wherein the transition metal salt is
based on at least one of a group consisting of iron, copper,
nickel, manganese and chromium.
12. The process of claim 10, wherein the counterion is an organic
or inorganic counterion.
13. The process of claim 10, wherein the transition metal salt
comprises a complex counterion.
14. The process of claim 10, wherein the catalyst is readily
removed from the (co)polymer by washing with a solvent.
15. The process of claim 14, wherein the solvent is a polar
solvent.
16. The process of claim 15, wherein the polar solvent is
water.
17. The process of claim 13, wherein the complex counterion is an
onium based counterion.
18. The process of claim 17, wherein the onium based counterion is
a charged species comprising at least one atom chosen from a group
consisting of N, P, or As.
19. The process of claim 18, wherein the counterion comprises a
material chosen from a group consisting of aliphatic amines,
phosphines, and arsenes.
20. The process of claim 19, wherein the counterion comprises a
material chosen from a group consisting of tetra-alkylammonium,
tetra-alkylphosphonium, and tetra-alkylarseonium counterions.
21. The process of claim 13, wherein the transition metal salt
comprises a metal based counterion
22. The process of claim 13, wherein the transition metal salt
comprises a halide counterion.
23. The process of claim 13, wherein the transition metal salt is
arranged in one of a tetrahedral and a square planar configuration
with the counterion.
24. The process of claim 13, wherein a molar ratio of the
transition metal to the counterion is greater than one.
25. The process of claim 24, wherein the transition metal is
iron.
26. The process of claim 1, further comprising: adding a neutral
ligand to increase the rate of reaction.
27. A controlled polymerization process, comprising: preparing a
second initiator having a radically transferable atom or group by
decomposing a first standard free radical initiator in the presence
of a transition metal salt, the transition metal salt comprising: a
complex counterion; and a radically transferable atom or group,
wherein the transition metal salt transfers the radically
transferable atom or group to a decomposition product of the first
initiator to form the second initiator; polymerizing free radically
(co)polymerizable monomers in the presence of a system initially
comprising: the second initiator; and a catalyst which participates
in a reversible cycle with at least one of the second initiator and
a compound having a radically transferable atom or group.
28. The process of claim 27, wherein the catalyst is the transition
metal salt.
29. The process of claim 28, wherein the transition metal salt
initially present comprises a transition metal in a higher
oxidation state and a transition metal in the metal zero state such
that the average oxidation state is lower than that required to
react with the molar ratio of initiator.
30. The process of claim 28, wherein the transition metal is
iron.
31. The process of claim 27, wherein a polymer is formed having a
partial residue of the first initiator at one terminus.
32. The process of claim 31 further comprising: isolating the
polymer.
33. The process of claim 27, wherein the process is performed in
one of a bulk system, a system comprising an appropriate solvent,
in a suspension, in an emulsion, or over a solid support in a
batch, semi-batch or continuous process.
34. The process of claim 27, wherein the complex counterion
comprises a charged ligand.
35. A controlled polymerization process, comprising: preparing an
initiator having a radically transferable atom or group by
rupturing a peroxide in the presence of a transition metal salt,
the transition metal complex comprising: a radically transferable
atom or group, wherein the transition metal complex transfers the
radically transferable atom or group to a residue of the peroxide
to form the initiator or originator; polymerizing free radically
(co)polymerizable monomers in the presence of a system initially
comprising: the initiator; and a catalyst which participates in a
reversible cycle with the initiator and a compound having a
radically transferable atom or group.
36. The process of claim 35, wherein the transition metal complex
comprises a transition metal salt.
37. The process of claim 35, wherein the transition metal is
copper.
38. The process of claim 35, wherein the transition metal complex
comprises a metal in a lower oxidation state.
39. The process of claim 35, wherein a polymer is formed having a
partial residue of the peroxide at one terminus.
40. The process of claim 39, further comprising: isolating the
polymer.
41. The process for controlled polymerization of radically
(co)polymerizable monomers, comprising the steps: polymerizing one
or more free radically (co)polymerizable monomers in the presence
of a system comprising: an initiator having a first radically
transferable atom or group and a carboxylic acid group, and a
transition metal complex capable of undergoing a redox reaction
with the initiator or a compound having a radically transferable
atom or group, to allow addition of said radically polymerizable
(co)monomers to initiator.
42. The process of claim 41, further comprising: forming a
(co)polymer with a terminal carboxylic acid group; and isolating
the (co)polymer.
43. A process for controlled polymerization of radically
(co)polymerizable monomers containing free carboxylic acid groups
comprising the steps: polymerizing a first free radically
(co)polymerizable monomers and a second free radically
(co)polymerizable monomers having a free carboxylic acid group in
the presence of: an initiator containing a radically transferable
atom or group; and a transition metal complex capable of undergoing
a redox reaction with the initiator and a compound having a
radically transferable atom or group, to allow addition of said
radically polymerizable (co)monomers
44. The process of claim 43, further comprising: forming a
(co)polymer with a carboxylic acid group within the polymer chain;
and isolating the (co)polymer.
45. A controlled polymerization process of atom or group transfer
polymerization, comprising the steps: polymerizing one or more
radically (co)polymerizable monomers in the presence of a system
initially containing; an initiator having one or more radically
transferable atom(s) or group(s), a transition metal compound
comprising one or more counterion(s) attached to a solid support,
which interacts with a N-, O-, P-, or S-containing ligand which can
coordinate in a .sigma.-bond, or a carbon-containing ligand which
can coordinate in a .pi.-bond, to the transition metal; and wherein
the transition metal compound participates in a reversible redox
cycle with the initiator or a compound having a radically
transferable atom or group.
46. The process of claim 45, further comprising: preparing the
initiator having a radically transferable atom or group by
decomposing a first standard free radical initiator to a radical in
the presence of the transition metal compound in a higher oxidation
state, the transition metal compound comprising: a radically
transferable atom or group, wherein the transition metal compound
transfers the radically transferable atom or group to the radical
of the first initiator to form the initiator and the transition
metal salt in a lower oxidation state.
47. The process of claim 45, wherein the transition metal compound
is physically, physicochemically or chemically attached to the
surface of the solid support through ionic bonding, physisorption,
chemisorption, Van der Waals forces, coordinate or covalent
bonding.
48. A controlled polymerization process of atom or group transfer
polymerization, comprising the steps: polymerizing one or more
radically (co)polymerizable monomers in the presence of a system
initially containing; an initiator having one or more radically
transferable atom(s) or group(s), a transition metal salt
comprising one or more counterion(s) attached to a solid support;
wherein the transition metal catalyst participates in a reversible
redox cycle with the initiator or a compound having a radically
transferable atom or group.
49. The process of claim 48 wherein the transition metal salt
comprises a complex counterion.
50. A controlled polymerization process of atom or group transfer
polymerization, comprising the steps: polymerizing one or more
radically polymerizable monomers in the presence of a system
initially comprising: an initiator having one or more radically
transferable atom(s) or group(s); a transition metal salt
comprising: one or more of the counterion(s) attached to a solid
support; a ligand coordinated in a .sigma.-bond to the transition
metal, a redox conjugate of the transition metal compound; wherein
at least one of the transition metal and a redox conjugate of the
transaction metal salt participate in a reversible redox cycle with
at least on of the initiator or a compound having a radically
transferable atom or group.
51. The process of claim 50, wherein the redox conjugate of the
transition metal is at least partially soluble in the
polymerization process.
52. The process of claim 50, wherein the solid support is an ion
exchange resin.
53. The process of claim 50, wherein the process is conducted in a
batch reactor.
54. The process of claim 50, wherein the process is conducted in a
continuous flow system.
55. The process of claim 50, further comprising: forming the
initiator by transferring a radically transferable atom or group
from the transition metal salt in a higher oxidation state to a
formed free radical.
56. A process for the removal of a transition metal catalyst
complex from a polymerization reaction comprising the steps:
contacting a reaction medium to an ion exchange medium wherein the
reaction medium comprises: a polymer; a catalyst complex.
57. The process of claim 56, wherein the reaction medium further
comprises a solvent.
58. The process of claim 57, wherein the solvent has a polarity
which enhances the rate of removal of the catalyst complex from the
medium.
59. The process of claim 56, wherein the ion exchange resin
comprises a crosslink density and a bead size, wherein at least one
of the crosslink density and the bead size is chosen to enhance
removal of the catalyst complex.
60. The process of claim 56, wherein the catalyst complex is
present in the reaction medium comprising at least one of a
solution, an emulsion or miniemulsion.
61. The process of claim 60, wherein the emulsion or miniemulsion
comprises a suspension medium of an inorganic liquid.
62. The process of claim 60, wherein the emulsion or miniemulsion
comprises a suspension medium of water.
63. The process of claim 56, wherein the catalyst complex
comprises: a transition metal in one or more oxidation states; a
ligand; and a counterion.
64. The process of claim 63, wherein the catalyst complex is bound
to the ion exchange medium through a shared counterion on the ion
exchange medium.
65. The process of claim 63, wherein the reaction medium is passed
over a bed of the ion exchange medium.
66. The process of claim 63, wherein the ligand on the catalyst
complex is chosen to allow efficient removal of the transition
metal complex from solution by the ion exchange medium.
67. The process of claim 63, wherein the temperature of the
reaction media is controlled to modify the rate of removal of
transition metal from the reaction media.
68. The process of claim 63, wherein the transition metal is one of
either copper or iron.
69. The process of claim 63, further comprising: separating the ion
exchange medium from the reaction medium.
70. The process of claim 69, further comprising: regenerating the
catalyst complex.
71. The process of claim 70, wherein regenerating the catalyst
complex comprises: exposing the ion exchange medium bound
transition metal complex to a regeneration medium containing one of
an acid or a salt comprising a radically transferable atom or group
as a counterion; separating the regeneration medium from the ion
exchange resin.
72. The process of claim 71, wherein the regeneration medium
contains free radically (co)polymerizable monomers.
73. The process of claim 71, wherein the equilibrium between the
transition metal complex in solution and transition metal complex
bound to the ion exchange resin is controlled by adjusting one or
more of the temperature of the regeneration medium, polarity of the
regeneration medium, ionic character of the ion exchange resin, pH
of the regeneration medium, degree of crosslinking of the ion
exchange resin or swellability of the ion exchange resin,
swellability permeability of the ion exchange resin, acid strength
of the supported counterion and gross size of the ion exchange
resins.
74. The process of claim 56, wherein the catalyst complex comprises
a complex salt.
75. The process of claim 56, wherein the catalyst complex
comprises: a transition metal; and a complex counterion.
76. The process of claim 75, wherein the ion exchange medium is an
ion exchange resin.
77. The process of claim 56, wherein the ion exchange medium has
acidic counterions.
78. The process of claim 56, wherein the ion exchange medium
comprises cations selected of at least one of H.sup.+ or
Na.sup.+.
79. The process of claim 56, wherein the catalyst complex is bound
to the ion exchange medium through a shared counterion on the ion
exchange medium.
80. The process of claim 56, wherein substantially all of the
catalyst complex is removed from the reaction medium.
81. A controlled polymerization process, comprising: polymerizing
free radically (co)polymerizable monomers in the presence of a
system comprising: an initiator having a radically transferable
halide; a transition metal compound; and a nitrogen containing
ligand.
82. The process of claim 81, wherein the free radically
(co)polymerizable monomers are (meth)acrylamides.
83. The process of claim 81, wherein the ligand is at least one of
a primary or secondary linear amine.
84. The process of claim 83, wherein the ligand is further
complexed by a polar solvent to prepare a neutral complex.
85. The process of claim 81, wherein the ligand is a charged
species.
86. A process for atom transfer radical addition for adding
functionality to an oligomer or polymer, comprising: reacting a
first oligomer or polymer having a radically transferable atom or
group with a second compound having a first desired functional
group, the second compound reactive with the first oligomer or
polymer after removal of the radically transferable atom or group,
in the presence of a system initially comprising: a catalyst which
participates in a reversible cycle with the first oligomer or
polymer.
87. The process of claim 86, wherein the catalyst comprises a
transition metal salt.
88. The process of claim 86, wherein the catalyst comprises a
transition metal and further comprising: adding the transition
metal in its metal zero state.
89. The process of claim 86, wherein the second compound is not a
free radically polymerizable monomer.
90. The process of claim 89, wherein the second compound comprises
.alpha.,.alpha.-disubstituted olefin group.
91. The process of claim 86, wherein the catalyst is a transition
metal complex.
92. The process of claim 91, wherein the transition metal complex
comprising a transition metal and a ligand further comprising
adding additional transition metal and, optionally, additional
ligand.
93. The process of claim 86, further comprising forming a second
oligomer or polymer which is not polymerizable in the system.
94. The process of claim 93, further comprising reacting the second
oligomer or polymer with a second compound which is reactive with
the second oligomer or polymer, wherein the second compound has a
second desired functional group.
95. The process of claim 94, wherein the second compound
additionally comprises a fourth desired functional group, the
functional groups are thereby incorporated into the polymer at each
reactive chain end, wherein the third compound has a
structure:CH.sub.2.dbd.CR.sup.1--(CH.sub.2).sub.- n--Xwherein
R.sup.1 is on selected from H, CH.sub.3 or aryl; n is an integer;
and, X is a functional group.
96. The process of claim 86, wherein the first oligomer or polymer
has a plurality of radically transferable atoms or groups.
97. The process of claim 93, wherein the second polymer is one of a
homotelechelic-polymer or a heterotelechelic polymer.
98. The process of claim 97, wherein the second desired functional
group is subject to further reaction conditions to convert the
second functional group into a third functional group.
99. The process of claim 98, wherein the said further reaction
forms a double bond.
100. The process of claim 99, wherein the said further reaction
includes a dehydrohalogenation reaction.
101. The process of claim 100, wherein the reaction is assisted by
the presence of an acid acceptor.
102. The process of claim 86, wherein the second compound is an
unsaturated molecule which is not free radically (co)polymerizable
and terminates the polymer.
103. The process of claim 102, wherein the unsaturated molecule
comprises a second functional group.
104. The process of claim 103, further comprising: adding a third
compound comprising a third functional group, the third compound
which reacts with the first functional group incorporated on the
polymer.
105. The process of claim 102, wherein the unsaturated molecule is
at least one of .alpha.,.alpha.-disubstituted olefin or an
allyl.
106. The process of claim 94, wherein the second desired functional
group comprises one of an allyl, epoxy, hydroxy, amino, cyano,
carboxy, masked carboxy, alkyl, perhaloalky, silyl, silicon
containing moiety or phosphorous containing moiety.
107. A process for a catalytic atom transfer functionalization of
oligo/polymeric materials having one or more radically transferable
atom(s) or group(s), comprising the steps: providing a polymer
having a radically transferable atom or group; and adding a
compound containing a .alpha.,.alpha.-disubstituted olefin group to
the polymer in the presence of a transition metal complex capable
of undergoing a redox reaction with the radically transferable atom
or group, resulting in the addition of the compound containing the
.alpha.,.alpha.-disubstituted olefin group at the site of the
radically transferable atom or group and an elimination reaction
involving the radically transferable atom or group to form a
reactive unsaturated group.
108. The process of claim 107, wherein the substituents on the
.alpha.,.alpha.-disubstituted olefin group are individually
selected.
109. The process of claim 108, further comprising: forming a
functional polymer having a reactive exo-double bond and wherein
one of the substituents is a methyl group.
110. The process of claim 109, further comprising: forming a
functional polymer having an endo-double bond.
111. The process of claim 110, wherein the coupling compound
comprises an .alpha.-aryl styrene.
112. The process of claim 111, wherein the .alpha.-aryl styrene is
selected from diphenylethylene, 1,3-bis(1-phenylethenyl)benzene, or
2,2-bis{4-(1-phenylethenyl)phenyl}propane.
113. The process of claim 107, wherein the polymeric material is an
oligimer.
114. The process of claim 107, wherein one substituant on the
.alpha.,.alpha.-disubstituted olefin is a methyl group and the
formed double bond is predominately a exo-double bond.
115. The process of claim 114, wherein a macromonomer with a
reactive exo-double bond is prepared.
116. The process of claim 107, wherein the elimination reaction is
enhanced by the addition of an acid acceptor.
117. The process of claim 116, wherein the acid acceptor is
selected from the group consisting of basic organic molecules,
linear and heterocyclic N containing compounds, ion exchange resins
or inorganic acid acceptors.
118. A process for a catalytic atom transfer coupling of polymers
comprising: providing a first polymer having a first radically
transferable atom or group; adding a coupling compound containing
one or more .alpha.,.alpha.-disubstituted olefin group(s) to the
first polymer in the presence of a transition metal complex capable
of undergoing a redox reaction with the first radically
transferable atom or group, resulting in the addition of the
coupling compound containing the .alpha.,.alpha.-disubstituted
olefin group at the site of the first radically transferable atom
or group and an elimination reaction comprising the radically
transferable atom or group to form a reactive double bond; and
allowing a second polymer having a second radically transferable
atom or group in the presence of the transition metal complex to
add to the reactive double bond.
119. The process of claim 118, wherein the first polymer and the
second polymer are substantially similar.
120. The process of claim 119, fturther comprising: forming a
functional polymer having an endo-bond and wherein the coupling
compound comprises an .alpha.-alkyl styrene.
121. The process of claim 120, wherein the coupling compound
comprises ac-methyl styrene.
122. The process of claim 107, further comprising: forming a
functional polymer comprising and enol/ketone and wherein an
.alpha.-substituent comprises a hydroxyl group.
123. The process of claim 118, wherein the coupling compound is a
second polymer comprising an isopropenyl group.
124. The process of claim 123, wherein the
.alpha.,.alpha.-disubstituted olefin group is a pendant functional
group of the second polymer.
125. The process of claim 123, wherein the graft copolymer comprise
the first copolymer grafted to the second copolymer within the
graft copolymer chain.
126. The process of claim 118, the first polymer is a mixture of
(co)polymers.
127. The process of claim 118, wherein the second polymer has a
similar composition and molecular weight to the first polymer.
128. The process of claim 118, wherein a molar ratio of the total
moles of the first polymer and the second polymer to the moles of
the coupling compound is controlled to form a third polymer of a
configuration of at least one of linear, star, graft, and chain
extended materials containing a residue of the first polymer and
the second polymer.
129. The process of claim 128, wherein the first polymer includes
two transferable atoms or groups and the coupling compound contains
two .alpha.,.alpha.-disubstituted olefin groups allowing the
formation of a network copolymer containing multiple units of the
first polymer.
130. The process of claim 128, wherein the coupling compound
contains one .alpha.,.alpha.-disubstituted olefin group, the first
polymer and second polymer have one radically transferable atom or
group and a molar ratio of the total moles of the first polymer and
the second polymer to the moles of the coupling compound is
essentially 1:0.5.
131. The process of claim 128, wherein the coupling compound
contains two .alpha.,.alpha.-disubstituted olefin groups, the first
polymer and second polymer each have one radically transferable
atom or group and the molar ratio of the total moles of the first
polymer and the second polymer to the moles coupling compound is
essentially 1:0.25.
132. The process of claim 131, wherein the first polymer and the
second polymer differ in at least one of molecular weight and
composition and a star copolymer is formed.
133. The process of claim 132, wherein a hetero-arm star copolymer
is formed.
134. The process of claim 131, wherein two
.alpha.,.alpha.-disubstituted olefin groups differ in reactivity
characteristics.
135. The process of claim 128, wherein the coupling compound is a
compact molecule and contains three .alpha.,.alpha.-disubstituted
olefin groups and wherein the molar ratio is controlled to form a
star copolymer with up to six arms.
136. The process of claim 118, wherein the coupling compound
contains two .alpha.,.alpha.-disubstituted olefin groups of
different reactivities and the first polymer and second polymer
each have two radically transferable atoms or groups resulting in
one of an extended chain or coupled polymer with an
.alpha.,.alpha.-disubstituted olefin group within the chain.
137. The process of claim 126, wherein the coupling compound
contains three .alpha.,.alpha.-disubstituted olefin groups and the
molar ratio of the total moles of the first polymer and the second
polymer to the moles coupling compound is controlled to form a star
polymer with up to six arms.
138. The process according to 128, wherein the molar ration is
1:0.167.
139. The process of claim 118, wherein the coupling compound
comprises a third polymer.
140. A star copolymer, comprising segments of free radically
polymerizable monomers wherein two or more arms have a different
composition from the other arms.
141. A star copolymer produced by the process of claim 128, wherein
the first polymer and the second polymer are different.
142. The star copolymer of claim 141, wherein the first polymer
differs from the second polymer in at least one of molecular weight
or composition.
143. A graft copolymer with a backbone polymer with incorporated
coupling compounds and a grafted polymer produced by process of
claim 118.
144. The graft copolymer of claim 143, wherein the backbone polymer
is produced by an addition or condensation polymerization
process.
145. The graft copolymer of claim 143, wherein the backbone polymer
is a polyolefin.
146. The graft copolymer of claim 143, wherein the backbone polymer
comprises blocks of at least one of polystyrene, polyethylene,
polypropylene, polyisobutylene, polybutadiene or polyisoprene.
147. An .alpha.-substituted olefin, comprising an exo-double bond,
suitable for use as a macromonomer, in which the
.alpha.-substituant is a free radically (co)polymerized
oligo/polymer with a molecular weight greater than 250 possessing a
known group at the other terminus of the polymer.
148. An .alpha.,.beta.-disubstituted olefin comprising two
substituants, wherein each substituant is a free radically
(co)polymerized oligo/polymer with a molecular weight greater than
250.
149. A macromonomer comprising: a functional group containing a
terminal exo-olefin double bond derived from free radically
(co)polymerizable monomers; a stereochemistry and tacticity of a
material formed by a free radical polymerization process; and a
symmetrical single peak molecular weight distribution less than
1.5.
150. The macromonomer of claim 149, wherein the functionality is
greater than 90 mole %.
151. A controlled polymerization process, comprising: adding a core
forming compound to an active atom transfer radical polymerization
process; and forming a multi-arm star copolymer wherein polymers
react with the core forming compound to form the star compound.
152. The process of claim 151, further comprising: adding a
plurality of initiators, wherein each initiator includes: a
radically transferable atom or group; and optionally, a functional
group.
153. The process of claim 152, wherein the core forming compound is
a divinyl compound.
154. The process of claim 153, wherein the multi-arm star polymer
includes a single well defined core.
155. The process of claim 153, wherein the multi-arm star polymer
includes a core having core compound to core compound coupling.
156. The process of claim 153, wherein the multi-arm star polymer
includes a network of coupled core compounds.
157. The process of claim 153, wherein the resulting multi-arm star
polymer is a one of a gel or crosslinked system.
158. The process of claim 153, wherein the divinyl compound is one
of a divinyl aryl compound, a di-acrylate or a di-methacrylate.
159. A telefunctional multi-arm star copolymer comprising: a core
comprising core unit to core unit coupling; a plurality of arms
synthesized from radically polymerizable monomers attached to at
least one of the core units; and a known level of functional groups
on the termini of each polymer chain.
160. A crosslinked or gel-like telefunctional multi-arm star
copolymer comprising: at least two core units; a plurality of arms
synthesized from radically polymerizable monomers attached to at
least one of a core unit and another arm forming a matrix; and a
known level of functional groups with in the matrix.
161. A telefunctional network copolymer produced by the process of
claim 141, wherein: the average number of radically transferable
atoms or groups per first polymer is greater than one; and the core
compound is a divinyl compound.
162. A telefunctional multi-arm star copolymer wherein the arms of
the copolymer are composed of different copolymers displaying
differing properties.
163. A polymerization or telomerization process for preparation of
polyvinyl acetate with a predetermined molecular weight range
comprising: polymerizing a vinyl acetate monomer in the presence of
a system comprising: an initiator having a radically transferable
atom or group, wherein in the initiator is also capable of acting
as a chain transfer agent; and a transition metal complex which
participates in a redox reaction with at least one atom or group of
the initiator having a radically transferable atom or group, the
transition metal complex comprising: transition metal; a ligand
coordinated with the transition metal to form a partially soluble
transition metal complex.
164. The process of claim 163, further comprising: forming
polyvinyl acetate having a radically transferable atom at one
polymer end; and optionally, isolating the polyvinyl acetate.
165. The process of claim 163, wherein the chain transfer rate
constant of the initiator in the system is about one and remains
substantially constant throughout the polymerization.
166. The process of claim 163, wherein the initiator is at least
one of carbon tetrahalide or an alkyltrihalide.
167. The process of claim 166, wherein the halide is a bromide or a
chloride.
168. The process of claim 163, wherein the transition metal is
iron.
169. The process of claim 168, wherein the ligand is a linear
amine.
170. The process of claim 169, wherein the ligand is a
tetramine.
171. The process of claim 163, wherein the transition metal complex
further comprises: a counterion which is not a radically
transferable atom or group.
172. The process of claim 171, wherein the counterion is an
acetate.
173. The process of claim 163, further comprises: controlling the
polymerization by adding a predetermined amount of initiator based
on the amount of vinyl acetate to be polymerized; forming polyvinyl
acetate of a predetermined average molecular weight.
174. The process of claim 163, wherein the polymerization is a
telomerization and further comprising: forming a polyvinyl acetate
telomer.
175. The process of claim 174, further comprising: controlling the
telomerization by adding a predetermined amount of initiator based
on the amount of vinyl acetate to be telomerized, wherein the
initiator is one of carbon tetrahalide or an alkyltrihalide group
on a molecule having at least one alkyltrihalide group; and forming
the polyvinyl acetate telomer at a predetermined average molecular
weight.
176. The process of claim 175, wherein the polyvinyl acetate has a
terminal radically transferable atom or group.
177. The process of claim 174, wherein the molecular weight of the
polyvinyl acetate telomer is less than 1,000,000.
178. The process of claim 174, wherein the molecular weight of the
polyvinyl acetate telomer is between 1,000 and 100,000.
179. The process of claim 175, further comprising: converting the
vinyl acetate telomer into a alkoxyamine macroinitiator.
180. A process for the preparation of vinyl acetate block
copolymers comprising: polymerizing free radically
(co)polymerizable monomer in the presence of a system initially
comprising: a polyvinyl acetate based macroinitiator having a
radically transferable atom or group; and a catalyst which
participates in a reversible cycle with at lease one of the
macroinitiator and a compound having a radically transferable atom
or group.
181. The process of claim 180, further comprising: first preparing
a polyvinyl acetate based macoinitiator comprising: polymerizing a
vinyl acetate monomer in the presence of a second system
comprising: an second initiator having a second radically
transferable atom or group, wherein the second initiator is also
capable of acting as a chain transfer agent; and a partially
soluble transition metal catalyst which participates in a redox
cycle with the second initiator and in a reversible cycle with the
polyvinyl acetate macroinitiator or a compound having a radically
transferable atom or group, the transition metal catalyst
comprising: a transition metal; a ligand coordinated with the
transition metal to form the transition metal complex.
182. The process of claim 181, wherein the second initiator
includes a alkyltrihalide group and the polyvinyl acetate based
macroinitiator contains two telechelic groups having a radically
transferable atom or group.
183. The process of claim 182, wherein the alkyltrihalide is an
alkyldichlorobromo-group and the telechelic groups have terminal
bromo groups.
184. The process of claim 181, wherein preparing a polyvinyl
acetate based macroinitiator further comprises: isolating the
polyvinyl acetate based macroinitiator.
185. The process of claim 181, wherein the catalyst is the
transition metal complex.
186. A process for the preparation of block copolymers, comprising:
preparing a radically (co)polymerizable polymer comprising:
polymerizing a first radically (co)polymerizable monomer in the
presence of a first system comprising: an initiator having a
radically transferable atom or group, wherein the initiator is also
capable of acting as a chain transfer agent; and a transition metal
complex which participates in a reversible cycle with at least one
of the initiator and a compound having a radically transferable
atom or group; adding and polymerizing a second free radically
(co)polymerizable monomer in the presence of a second system
initially comprising: the radically (co)polymerizable polymer
having a radically transferable atom or group, wherein the
radically (co)polymerizable polymer acts as the initiator; and the
transition metal complex, wherein the transition metal complex is
at least partially soluble in the second system and participates in
a reversible cycle with at least one of the radically
(co)polymerizable polymer and a compound having a radically
transferable atom or group; and optionally, isolating the block
copolymer.
187. The process of claim 186, wherein the second system further
comprises: the first radically copolymerizable monomer.
188. A block copolymer, comprising: a first block synthesized from
vinyl acetate monomers; and a second block of free radically
copolymerizable monomers attached to the first block.
189. A process for the preparation of block copolymers comprising:
polymerizing a first (co)polymer block by a first reaction
mechanism catalyzed by a transition metal; and polymerizing a
second (co)polymer block by a second reaction mechanism catalyzed
by the transition metal, wherein the first reaction mechanism is
different than the second reaction mechanism.
190. A block copolymer, comprising: a first block synthesized from
vinyl acetate monomers; and a second block synthesized from free
radically copolymerizable monomers and, optionally, having
functional end groups.
191. The process of preparing a block copolymer, comprising the
steps of: providing a block copolymer comprising: a first block
synthesized from vinyl acetate monomers; and a second block of free
radically copolymerizable monomers having functional end groups;
converting the functional end group into a different group.
192. An ABA block copolymer having functional end groups,
comprising: two A blocks synthesized from vinyl acetate monomers;
and a B block synthesized from free radically copolymerizable
monomers.
193. The process of preparing a ABA block copolymer, comprising the
steps of: providing an ABA block copolymer having functional groups
comprising: two A blocks synthesized from vinyl acetate monomers;
and a B block synthesized from free radically copolymerizable
monomers; and converting the functional end group into a different
group.
194. An AB star copolymer, comprising: an A block synthesized from
vinyl acetate monomers; and a B block synthesized from free
radically copolymerizable monomers.
195. A block copolymer comprising: a first block synthesized from
vinyl acetate monomers; and a second block synthesized from
(meth)acrylate monomers.
196. A polymerization process for the preparation of homopolymers
and block polymers with (meth)acrylamide monomers comprising:
copolymerizing a (meth)acrymide monomer in the presence of a system
initially comprising: a initiator having a radically transferable
atom or group; and a transition metal complex which participates in
a reversible redox cycle with at lease one of the macroinitiator
and a compound having a radically transferable atom or group,
wherein the transition metal complex allows addition of several
monomer units during each reversible redox cycle; forming a
polymer.
197. The process of claim 196, wherein the initiator is a
macroinitiator.
198. A (meth)acrylate-block-(meth)acrylamide copolymer produced by
the polymerization process of claim 196.
199. A controlled suspension or emulsion polymerization process
comprising: polymerizing free radically (co)polymerizable monomers
in the presence of a system initially comprising: a suspending
medium; a surfactant; an initiator having a radically transferable
atom or group; and a transition metal complex which participates in
a reversible redox cycle with at least one of the initiator and a
compound having a radically transferable atom or group, wherein the
redox conjugate of the catalyst transition metal is added to the
suspending medium.
200. The process of claim 199, wherein the hydrophobicity and
hydrophylicity of the transition metal complex is controlled by the
choice of one of the ligands or the substituents on the
ligands.
201. The process of claim 200, further comprising: adding a second
free radically (co)polymerizable monomer; and optionally, adding at
least one of the transition metal complex, the transition metal
compound, the transition metal redox conjugate, a counterion
comprising a second radically transferable atom or group, and a
ligand.
202. The process of claim 199, wherein the transition metal complex
comprises a picolyl amine.
203. The process of claim 199, wherein the polymerization is
initiated by the decomposition of a standard radical initiator.
204. An emulsion controlled radical polymerization process,
comprising: providing a suspension medium; adding a standard free
radical initiator, initiating the polymerization by decomposition
of the standard free radical initiator, in the presence of
radically (co)polymerizable monomers adding a transition metal
compound in a higher oxidation state comprising a radically
transferable atom or group, wherein the radically transferable
group transfers to the residue of the standard free radical
initiator to form a second initiator; and adding a third initiator
having a radically transferable atom or group.
205. The process of claim 204, further comprising: forming an
emulsion in the suspending medium, wherein the particle size of the
emulsion is controlled by the decomposition of the standard free
radical initiator and the polymerization process is controlled by
the second and the third initiators.
206. A controlled radical polymerization process, comprising:
contacting an initiator attached to a solid surface to a solution
comprising: a plurality of free radically polymerizable monomers;
and a persistent free radical formed in the controlled radical
polymerization.
207. The process of claim 206, further comprising: a free radically
(co)polymerizable monomer; and a persistent free radical or
deactivator.
208. The process of claim 207, further comprising a transition
metal compound as the persistent free radical or deactivator.
209. The process of claim 207, wherein the persistent free radical
is greater than 1% of the solution.
210. The process of claim 207, wherein the persistent free radical
is greater than 3% of the solution.
211. The process of claim 207, wherein the persistent free radical
is greater than 1% of the system and the monomer.
212. The process of claim 207, wherein the persistent free radical
is greater than 3% of the system and the monomer.
213. The process of claim 207, wherein the persistent free radical
is the redox conjugate of a transition metal catalyst.
214. The process of claim 207, wherein the persistent free radical
is the stable free radical.
215. The process of claim 207, wherein the solid surface is one of
an inorganic surface or on inorganic particle.
216. The process of claim 207, wherein the initiator comprises a
functional group attached to the solid surface through a
non-aromatic group.
217. A controlled polymerization process, comprising: a
predetermined solvent concentration, wherein the solvent
concentration is predetermined to control the concentration of the
persistent free radical or deactivator
218. A controlled polymerization process, comprising: an
unsaturated monomer having an attached polyhedral oligomeric
silsesquioxane group.
219. The process of claim 218, wherein the unsaturated monomer is a
vinyl aromatic.
220. The process of claim 218, wherein the unsaturated monomer is a
(meth)acrylate.
221. The process of claim 218, further comprising: forming a
polymer.
222. The process of claim 221, wherein the polymer is a
homopolymer, a copolymer, a block copolymer, or a star block
polymer.
223. A homogeneous reverse atom transfer polymerization,
comprising: polymerizing free radically (co)polymerizable monomers
in the presence of a system initially comprising: a first standard
radical initiator, wherein the first standard radical initiator is
decomposed; a transition metal complex in a lower oxidation state
and having a radically transferable atom or group, wherein the
radically transferable atom or group is transferred to the residue
of the first standard radical initiator forming a second initiator,
wherein the transition metal complex participates is reversible
cycle with the second initiator and a compound having a radically
transferable atom or group; and forming a polymer.
224. A multifuictional star (co)polymer, comprising: a core
compound; a plurality of polymer arms synthesized from free
radically copolymerizable monomers having a functional end and an
attached end, wherein the attached end is attached to the core
compound; a functional group attached to the functional end of the
polymer arms.
225. The multifunctional star (co)polymer of claim 224, wherein in
the polymer arms are of controlled molecular weights and wherein
the functional groups present on the outer layer of the star
(co)polymer have been added by an atom transfer addition
reaction.
226. The polymer of claim 224, wherein the free radically
copolymerizable monomers include (meth)acrylates and (meth)acrylic
acids.
227. The multifunctional star (co)polymer, wherein the functional
group is selected from hydroxy, epoxy, amino, cyano, halide.
wherein the functional group us present on the functional end of
the polymer arms.
228. A controlled polymerization process for the preparation of
block copolymers, comprising: polymerizing a plurality of first
monomers into a polymer chain; polymerizing a second monomer into
the polymer chain, wherein a second monomer is polymerized while
some of the first monomer remains unpolymerized.
229. The process of claim 228, wherein the first and second
monomers are free radically polymerizable monomers, and
polymerizing the first and second monomers comprises a persistent
free radical, a deactivator, or a redox conjugate of the
catalyst.
230. The process of claim 229, wherein the system further comprises
a solvent.
231. The process of claim 228, wherein adding and polymerizing a
second free radically (co)polymerizable monomer is conducted after
75% of the first monomer is polymerized.
232. A block copolymer produced by the process of claim 231.
233. The process of claim 228, wherein adding and polymerizing a
second free radically (co)polymerizable monomer is conducted after
50% of the first monomer is polymerized.
234. A block copolymer produced by the process of claim 233.
235. A block copolymer, comprising: a first block synthesized from
a first monomer; a second block synthesized from a second monomer;
and a third block synthesized from both the first and second
monomer.
236. The block copolymer of claim 235, wherein the third block
comprises a gradient of the concentration of first monomers from
the first block to the second block.
237. The block copolymer of claim 236, wherein the third block
comprises a gradient of the concentration of first monomers from
the second block to the first block.
238. A process for the preparation of hybrid block copolymers
comprising: polymerizing free radically (co)polymerizable inorganic
monomer in the presence of a system initially comprising: a organic
based macroinitiator having a radically transferable atom or group;
and a catalyst which participates in a reversible cycle with at
lease one of the macroinitiator and a compound having a radically
transferable atom or group.
239. The process of claim 238, further comprising: converting an
organic polymer into the macroinitiator by modifying an end
group.
240. The process of claim 239, wherein modifying an end group
comprises converting a first end group into a second end group.
241. The process of claim 238, wherein the macroinitiator is a
phosphoramine.
242. A process for preparation of graft polymers, comprising:
(co)polymerizing a macromonomer in the presence of a macroinitiator
compatible with the macromonomer.
243. A process of claim 242, wherein (co)polymerizing comprises a
radical polymerization process and the macromonomer has a terminal
olefinic bond.
244. The process of claim 243, wherein the macromonomer includes a
terminal .alpha., .alpha.-disubstituted olefin group.
245. The process of claim 243, wherein the macromonomer includes a
terminal .alpha.-methylstyryl or isopropyl benzyl group.
246. The process of claim 242, further comprising: a catalyst which
participates in a reversible cycle with the macroinitiator; wherein
the macroinitiator is a macroinitiator having a radically
transferable atom or group.
247. A controlled polymerization process, comprising: polymerizing
free radically (co)polymerizable monomers in the presence of a
system initially comprising: an initiator having a radically
transferable atom or group; and a transition metal complex
comprising: a transition metal catalyst which participates in a
reversible cycle with at least one of the initiator and a compound
having a radically transferable atom or group, wherein transition
metal complex catalyst comprising: a ligand coordinated with the
transition metal and wherein the ligand is attached to a support.
forming a (co)polymer.
248. The process of claim 247, further comprising: adding a redox
conjugate of the transition metal to the reaction system.
249. The process of claim 248, wherein the redox conjugate of the
transition metal is added to the reaction system prior to the
initiation of the polymerization.
250. The process of claim 247, wherein the transition metal is in
both the higher and the lower oxidation states.
251. The process of claim 250, wherein the redox conjugate state of
the transition metal is present at 5 weight % of the total
transition metal.
252. The process of claim 247, wherein the ligand comprises a
linear amine.
253. The process of claim 252, wherein the linear amine is a linear
tetramine.
254. The process of claim 247, wherein the support is a polymeric
support.
255. A block copolymer, comprising: at least two blocks synthesized
from free radically (co)polymerizable monomers wherein one of more
blocks comprise a copolymer of the monomer(s) in the other block(s)
with a second monomer.
256. A block copolymer, comprising: at least two monomer blocks
synthesized by at least one of a first free radically
(co)polymerizable monomer and a second free radically
(co)polymerizable monomer, wherein at least one block comprises a
tapered copolymer.
257. An AB block copolymer, comprising: a first block synthesized
from a first free radically polymerizable monomer; a second block
synthesized from a second monomer and the first monomer, wherein
the concentration of the first monomer in the second block
increases the greater the distance from the first block along the
polymer chain.
258. The block polymer of claim 257, wherein the first monomer and
the second (co)monomer differ in phylicities.
259. A controlled polymerization process, comprising: polymerizing
free radically (co)polymerizable monomers in the presence of a
system at a polymerization temperature, the system initially
comprising: an initiator having a radically transferable atom or
group; a transition metal complex which participates in a
reversible cycle with at least one of the initiator and a compound
having a radically transferable atom or group; and a solvent;
forming a polymer, wherein the polymer is soluble in the solvent at
the polymerization temperature; altering at least one of the
temperature, the polarity or the pressure of the system to a
precipitation temperature wherein the polymer is not soluble in the
solvent.
260. The process of claim 259, wherein the transition metal complex
is soluble in the solvent at the polymerization temperature and the
precipitation temperature.
261. The process of claim 260, further comprising: separating the
polymer from the system.
262. The process of claim 261, wherein separating the polymer
comprises filtering the polymer from the system.
263. The process of claim 259, wherein the solvent is a polar
solvent.
264. The process of claim 259, wherein the solvent is a non-polar
solvent.
265. The process of claim 259, wherein the transition metal complex
comprises a ligand.
266. A controlled polymerization process, comprising: polymerizing
a first free radically (co)polymerizable monomer and a radically
copolymerizable monomer in the presence of a system initially
comprising: an initiator having a radically transferable atom or
group; and a catalyst which participates in a reversible cycle with
at least one of the initiator and a compound having a radically
transferable atom or group.
267. The process of claim 266, wherein the second free radically
copolymerizable monomer comprises a second functional group.
268. The process of claim 267, wherein the second functional group
comprises a polar substituent.
269. The process of claim 268, wherein the polar substituent is a
carboxylic acid group.
270. A homo-telechelic copolymer, comprising: a polymer synthesized
from free radically copolymerizable monomers having a first
terminal end and a second terminal end; a first functional group
attached to said first terminal end; a second functional group
attached to said second terminal end, wherein the said second
functional group has a different reactivity than said first
functional group.
271. The controlled polymerization process for the production of
telefunctional multi-arm star copolymers, comprising: polymerizing
a free radically (co)polymerizable monomer in the presence of a
system comprising: a telefunctional multi-armed star initiator
synthesized from free radically copolymerizable monomers, a first
initiator with one radically transferable atom or group, and a
divinyl compound.
272. The process of claim 271, wherein the first initiator further
comprises a second functional group.
273. The controlled polymerization process, comprising:
polymerizing a free radically (co)polymerizable monomer in the
presence of a system comprising: a transition metal catalyst
comprising a ligand.
274. The process of claim 273, wherein the ligand and the
substituents are chosen to control the hydrophylicity and the
hydrophobicity of the catalyst.
275. The process of claim 273, wherein the ligand and the
substituents are chosen to partition sufficient concentration of
the redox conjugate of the catalyst into the system to control the
polymerization.
276. The process of claim 273, wherein the structure of the ligand
is chosen to control the redox potential of the catalyst complex in
the polymerization system.
277. A graft copolymer, comprising: a polyolefin backbone polymer;
and a poly(meth)acrylate grafted on the backbone polymer.
278. The graft copolymer of claim 277, wherein the
poly(meth)acrylate comprises (meth)acrylic acid units.
279. A controlled polymerization process, comprising: a free
radically polymerizable monomer in the presence of a system
comprising: an initiator, wherein the initiator comprises a
radically transferable atom or group attached to the particle
surface through a non-aromatic linking group.
280. A process for the preparation of a composite structure,
comprising: polymerizing one or more free radically polymerizable
(co)monomers in the presence of an initiation system comprising: a
functional silica particle initiator comprising: a silica particle;
and a functional group containing a radically transferable atom; a
catalyst comprising a transition metal complex which participates
is a reversible cycle with at least one of the initiator and a
compound having a radically transferable atom or group.
281. The process of claim 280, wherein the silica particle is a
monodisperse particle.
282. A process for the preparation of a composite structure,
comprising: polymerizing one or more free radically polymerizable
(co)monomers in the presence of an initiation system comprising: a
functionalized nanotube initiator comprising: a functional group
containing a radically transferable atom; a catalyst comprising a
transition metal complex which participates is a reversible cycle
with at least one of the initiator and a compound having a
radically transferable atom or group.
283. A self reinforced nanocomposite comprising: a matrix
synthesized from free radically polymerizable monomers.
284. A process for removal of a catalyst from a polymerization
system, comprising: adding a compound to a polymerization system
comprising: a catalyst; and a polymer; wherein the compound causes
precipitation of the catalyst from the polymerization system by
interaction with the catalyst; filtering the reaction system to
remove the catalyst.
285. A process for removal of a catalyst from a polymerization
system, comprising: altering at least one parameter of a
polymerization system comprising: a catalyst; and a polymer;
wherein the parameters are selected from a group consisting of
polarity of the system, temperature and pressure which causes
precipitation of the catalyst from the polymerization system;
filtering the reaction system to remove the catalyst.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a nonprovisional application claiming
priority from U.S. Applications Serial Nos. 60/125,809 and
60/142,980.
BACKGROUND OF THE INVENTION
[0003] There is a continuing effort in polymer chemistry to develop
polymers that exhibit macro functionality or to develop new
functional polymers that possess specific chemical reactivity.
These developments would extend the level of control available to
materials engineers in processing polymers and using polymers as
building blocks in, or components for, subsequent material forming
reactions, such as copolymerization, chain extension and
crosslinking reactions, and interaction with substrates, including
dispersed solids. To be commercially useful, these reactions should
start from readily available, low cost monomers and produce
materials which are reactive during separate operations or during
fabrication, for example, by reaction injection molding,
compounding or alloying, and other processes to form coatings,
fibers, films, composite structures or bulk articles, with
modifiable and controllable desirable properties. A significant
economic hurdle that has to be overcome in this effort is to
provide the benefits of controlled polymerization, resulting in
greater control over the preparation of materials from such
available low cost monomers, exhibiting both micro- and
macro-functionality, in available commercial process equipment.
These long term objectives have provided the backdrop, or driving
force, for the continuing advances in controlled polymerization of
radically (co)polymerizable monomers, disclosed by some of the
present inventors in earlier applications, and provide the
incentive to extend, simplify and make more robust the process
known as atom transfer radical polymerization (ATRP).
[0004] The most evolved version of the classic ATRP reaction is
described in U.S. patent application Ser. No. 09/018,554, the
entire contents of which are hereby incorporated herein by
reference. Methods for exercising control over many parameters in a
catalytic process for the controlled polymerization of a wide range
of free radically (co)polymerizable monomers have been described in
publications authored or co-authored by Krzysztof Matyjaszewski and
others. See for example, Wang, J. S. and Matyjaszewsk, K., J. Am.
Chem. Soc., vol. 117, p.5614 (1995); Wang, J. S. and Matyjaszewsk,
K., Macromolecules, vol. 28, p. 7901 (1995); K. Matyjaszewski et
al., Science, vol. 272, p.866 (1996); K. Matyjaszewski et al.,
"Zerovalent Metals in Controlled/"living" Radical Polymerization,"
Macromolecules, vol. 30, pp. 7348-7350 (1997); J. Xia and K.
Matyjaszewski, "Controlled/"Living" Radical Polymerization.
Homogenous Reverse Atom Transfer Radical Polymerization Using AIBN
as the Initiator," Macromolecules, vol. 30, pp. 7692-7696 (1997);
U.S. Pat. Nos. 5,807,937 and 5,789,487, the contents of each of
which are hereby incorporated herein by reference. The subtle
interactions between the parameters have been further explored and
implementation of the teachings disclosed in these publications has
allowed the preparation of many inherently useful novel materials
displaying control over functionality and topology, and production
of novel tele-functional building blocks for further material
forming reactions, resulting from application of the site specific
functional and topological control attainable through this robust
controlled polymerization process for free radically
(co)polymerizable monomers.
[0005] The system or process employed to gain control over the
polymerization of free radically (co)polymerizable monomers has
been described in earlier applications as comprising the use of
four components: (i) an initiator molecule, or polymerization
originator molecule and (ii) a transition metal compound having
(iii) an added or associated counterion and the transition metal
compound complexed with (iv) a ligand(s). The initiator molecule,
or polymerization originator molecule can be any molecule
comprising one or more radically transferable atom(s) or group(s)
capable of participating in a reversible redox reaction with the
transition metal compound. The transition metal compound includes
an added or associated counterion. So that all reactive oxidation
states are soluble to some extent in the reaction medium, the
transition metal is complexed with ligand(s). The components of the
system are chosen to (co)polymerize the added monomers. See U.S.
Pat. No. 5,763,548, the entire contents of which are hereby
incorporated herein by reference.
[0006] In an embodiment known as "reverse" ATRP, the initiator
molecule described above can be formed in-situ by reaction of a
free radical with the redox conjugate of the transition metal
compound. Other components of the polymerization system such as the
choice of the radically transferable atom or group, counterion
initially present on the transition metal, and optional solvent can
influence the process. In addition, the functions of the components
of the system can be combined in a single molecule. U.S. Pat. No.
5,807,937 provides as an example of a single molecule containing a
combination of functions, a complex in which the counterion and
ligand are in one molecule. The role of the deactivator, the
"persistent radical," or for ATRP, the transition metal redox
conjugate, is also described in U.S. Pat. No. 5,807,937.
[0007] It is still often advantageous to think of the process
prerequisites individually so that one can conceptually consider
the conditions for control over every aspect of the process. For
example, if one wishes to introduce site specific functionality
into the resulting polymer one can either add an initiator, or
originator molecule containing the desired functional group, or a
masked functional group if the desired group can interact with the
transition metal complex, or one can utilize the radically
transferable atom or group which will be present at the active
growing polymer chain end(s) to introduce the desired functionality
to the product after polymerization is complete.
[0008] While not to be limited to the following description, the
theory behind ATRP is that polymerization proceeds essentially by
cleavage (and preferably essentially homolytic cleavage) of the
radically transferable atom or group from the rest of the initiator
molecule or, during the polymerization process the dormant polymer
chain end, by a reversible redox reaction with a complexed
transition metal catalyst, without any strong carbon-transition
(C-M.sub.t) bond formation between the active growing polymer chain
end and the transition metal complex. Within this theory as the
transition metal complex, in a lower active oxidation state, or in
its activator state, activates the initiator or dormant polymer
chain end by homolytically removing the radically transferable atom
or group from the initiating molecule, or growing polymer chain
end, in a reversible redox reaction, an active species is formed
that allows other chemistry, essentially free radical based
chemistry to be conducted. This is a reversible reaction. The
transition metal complex in the higher oxidation state, the redox
conjugate state or deactivator state, transfers a radically
transferable atom or group to the active initiator molecule or
growing chain end, thereby reforming the lower oxidation state
transition metal complex. When free radical based chemistry occurs,
a new molecule comprising a radically transferable atom or group is
also formed. In prior publications, the catalytically active
transition metal compound, which can be formed in situ or added as
a preformed complex, has been described as containing a range of
counterions. The counterion(s) may be the same as the radically
transferable atom or group present on the initiator, for example a
halide such as chlorine or bromine, or may be different radically
transferable atoms or groups. An example of the latter counterion
is a chloride counterion on the transition metal compound when the
initiator first contains a bromine. Such a combination allows for
efficient initiation of the polymerization followed by a controlled
rate of polymerization, and has additionally been shown to be
useful in certain crossover reactions, from one set of (co)monomers
to a second set of (co)monomers, allowing efficient formation of
block copolymers.
[0009] Presently, a wide variety of vinyl monomers can be
(co)polymerized in a controlled or "living" manner by this ATRP
technique with an increasing number of demonstrated transition
metals, e.g. copper, iron, nickel, ruthenium and rhodium in
conjunction with different ligands. Many ligands are available for
each transition metal used in ATRP, but, despite this, ligands that
are cheaper and better able to form catalytically active complexes
with improved redox potentials are still desired. In addition,
there is a continuing desire to identify catalyst complexes that
are amenable to recycle or reuse by known chemical manufacturing
processes.
BRIEF SUMMARY OF THE INVENTION
[0010] Several improvements will be disclosed and discussed herein
which simplify the atom transfer radical polymerization process and
make it more compatible with commercial practices, which should
reduce the overall cost for production of materials prepared by the
process. In addition, the improved process provides improved
functional materials for a number of useful applications.
[0011] The present invention includes a controlled polymerization
process comprising generally, polymerizing free radically
(co)polymerizable monomers and forming a (co)polymer. The free
radically (co)polymerizable monomers are polymerized in the
presence of a system which initially includes: an initiator having
a radically transferable atom or group and a catalyst which
participates in a reversible cycle with at least one of the
initiator and a compound having a radically transferable atom or
group. The catalyst most preferably comprises a transition metal
salt which may in one embodiment, includes a counterion, preferably
a complex counterion, such as an onium based counterion, or either
a halide or a metal based counterion. The free radically
(co)polymerizable monomers are preferably chosen from acrylates,
(meth)acrylates and (meth)acrylamides.
[0012] The present invention also provides a controlled
polymerization process of atom or group transfer polymerization
including polymerizing one or more radically (co)polymerizable
monomers in the presence of a polymerization system. The system
initially contains an initiator which has one or more radically
transferable atom(s) or group(s) and a transition metal compound
comprising one or more counterion(s) attached to a solid support.
The attached metal complex can comprise a transition metal compound
coordinated with ionic bonds to a complex counterion or a
transition metal compound which interacts with a N--, O--, P--, or
S-- containing ligand and coordinates in a .sigma.-bond, or
interacts with a carbon-containing ligand which can coordinate in a
.pi.-bond, to the transition metal. The transition metal compound
participates in a reversible redox cycle with the initiator or a
compound having a radically transferable atom or group. The
transition metal compound is one of physically, physicochemically
or chemically attached to the surface of the solid support through
ionic bonding, physisorption, chemisorption, Van der Waals forces,
coordinate or covalent bonding.
[0013] In one embodiment of the invention, the transition metal
compound comprises one or more counterion(s) attached to a solid
support, wherein one or more additional counterions are complex
counterions and the attached transition metal compound participates
in a reversible cycle with the initiator or a compound having a
radically transferable atom or group.
[0014] In another embodiment of the invention, the controlled
polymerization process includes polymerizing one or more radically
polymerizable monomers in the presence of a system initially
comprising an initiator and a transition metal compound. The
transition metal compound comprises one or more of the
counterion(s) attached to a solid support, a ligand coordinated in
a .sigma.-bond to the transition metal, a redox conjugate of the
transition metal compound. At least one of the transition metal and
redox conjugates participate in a reversible redox cycle with at
least on of the initiator or a compound having a radically
transferable atom or group. In this embodiment, the ligand may
contain a C atom which coordinates in a .pi.-bond to the transition
metal. The redox conjugate of the transition metal may be at least
partially soluble in the polymerization process. The solid support
may be an ion exchange resin. The process may be conducted in a
batch reactor or may be conducted in a continuous flow system. The
initiator may be formed by transferring a radically polymerizable
atom or group from the transition metal compound in a higher
oxidation state to a formed free radical.
[0015] In an alternative embodiment, the present invention provides
a process for atom transfer radical addition for adding
functionality to an oligomer or polymer. The process includes
reacting a first oligomer or polymer having a radically
transferable atom or group with a second compound having a first
desired functional group, the second compound reactive with the
first oligomer or polymer after removal of the radically
transferable atom or group, in the presence of a system initially
comprising a catalyst which participates in a reversible cycle with
the second compound. The catalyst is preferably a transition metal
complex, and may further comprise a ligand, and more preferably a
transition metal salt. The second compound is preferably an
unsaturated molecule which is not free radically (co)polymerizable,
terminating the polymer growth. The unsaturated molecule may
comprise a first functional group and may be at least one of an
.alpha.,.alpha.-disubstituted olefin or an allyl. The process may
include adding a molecule comprising a second functional group
wherein the molecule which reacts with the first functional group
is incorporated on the polymer. A third compound may be added
comprising a third functional group, wherein the third compound
reacts with the first functional group incorporated on the
polymer.
[0016] The present invention may also include a further embodiment
of the controlled polymerization process which includes preparing a
second initiator having a radically transferable atom or group by
decomposing a first free radical initiator in the presence of a
transition metal salt. In this embodiment, the transition metal
salt should comprise a complex counterion; and a radically
transferable atom or group. The transition metal salt transfers the
radically transferable atom or group to a decomposition product of
a first initiator to form the second initiator. Free radically
(co)polymerizable monomers are polymerized in the presence of a
system initially comprising the second initiator and a catalyst
which participates in a reversible cycle with at least one of the
second initiator and a compound having a radically transferable
atom or group. The polymer may preferably be formed having a
partial residue of the first initiator at one terminus. A further
step may include isolating the polymer. The transition metal salt
initially present is preferably in a higher oxidation state and a
transition metal in the metal zero state may be added such that the
average oxidation state is lower than that required to react with
the molar ratio of initiator. The process is performed in one of a
bulk system, a system comprising an appropriate solvent, in a
suspension, in an emulsion, or over a solid support in a batch,
semi-batch or continuous process.
[0017] The polymerization process of the present invention may
include preparing an initiator having a radically transferable atom
or group by rupturing a peroxide in the presence of a transition
metal compound where the transition metal compound in a lower
oxidation state comprises a radically transferable atom or group,
and the transition metal compound transfers the radically
transferable atom or group to a residue of the peroxide to form the
initiator or originator. The process further includes polymerizing
free radically (co)polymerizable monomers in the presence of a
system initially comprising the initiator and a catalyst which
participates in a reversible cycle with the initiator and a
compound having a radically transferable atom or group.
[0018] The controlled polymerization process of the present
invention may comprise polymerizing free radically
(co)polymerizable monomers, such as (meth)acrylamides, in the
presence of a system including an initiator having a radically
transferable halide, a transition metal compound, and a nitrogen
containing ligand, which is preferably at least one of a primary or
secondary linear amine. The ligand may be further complexed by a
polar solvent to prepare a neutral complex. The ligand may be a
charged species.
[0019] The invention further comprises a process for the removal of
a transition metal catalyst complex from a polymerization reaction.
The removal process comprises the steps of contacting a reaction
medium to an ion exchange medium wherein the reaction medium which
includes a polymer, optionally monomers, and a catalyst complex,
preferably comprised of a transition metal in one or more oxidation
states, a ligand, and one or more counterions. The catalyst complex
is optionally a complex salt, comprising a transition metal and a
complex counterion. The ion exchange medium preferably has acidic
counterions, and more preferably, cations selected from at least
one of H.sup.+ and Na.sup.+. The catalyst complex is bound to the
ion exchange resin through a shared counterion on the exchange
resin. The reaction medium may further include a solvent,
preferably having a polarity which enhances the rate of removal of
the catalyst complex from the medium and more preferably, wherein
substantially all of the catalyst complex is removed from the
reaction medium. The reaction medium is passed over a bed of the
ion exchange resin. The ligand on the catalyst complex is
preferably chosen to allow efficient removal of the transition
metal complex from solution by the ion exchange resin and the
process further includes separating the ion exchange resin from the
reaction medium.
[0020] The process may also include the further step of
regenerating the catalyst complex by exposing the ion exchange
resin bound transition metal complex to a regeneration medium
containing one of an acid or a salt comprising a radically
transferable atom or group as counterion, and separating the
regeneration medium from the ion exchange resin. The regeneration
medium may contains free radically (co)polymerizable monomers. The
equilibrium between the transition metal complex in solution and
transition metal complex bound to the ion exchange resin is most
preferably controlled by adjusting one or more of the polarity of
the regeneration medium, ionic character of the ion exchange resin,
pH of the regeneration medium, degree of crosslinking of the ion
exchange resin or swellability of the ion exchange resin,
swellability permeability of the ion exchange resin, acid strength
of the supported counterion and gross size of the ion exchange
resins.
[0021] The present invention also includes a process for a
catalytic atom transfer functionalization of oligo/polymeric
materials having one or more radically transferable atom(s) or
group(s). This embodiment of the process comprises the steps of
providing a polymer having a radically transferable atom or group,
adding a compound containing a .alpha.,.alpha.-disubstituted olefin
group to the polymer in the presence of a transition metal complex
capable of undergoing a redox reaction with the radically
transferable atom or group, resulting in the addition of the
compound containing the .alpha.,.alpha.-disubstituted olefin group
at the site of the radically transferable atom or group and an
elimination reaction involving the radically transferable atom or
group to form a reactive unsaturated group. The polymeric material
is optionally an oligomer. In a preferred format, one substituant
on the .alpha.,.alpha.-disubstituted olefin is a methyl group and
the formed double bond is predominately a exo-double bond. A
macromonomer with a reactive exo-double bond may be prepared. The
elimination reaction may be enhanced by the addition of an acid
acceptor preferably selected from the group consisting of basic
organic molecules, linear and heterocyclic N containing compounds,
ion exchange resins or inorganic acid acceptors.
[0022] In another embodiment of the invention, a process is
provided for a catalytic atom transfer coupling of polymers. The
coupling process includes providing a first polymer having a first
radically transferable atom or group, adding a coupling compound
containing one or more .alpha.,.alpha.-disubstituted olefin group
to the first polymer in the presence of a transition metal complex
capable of undergoing a redox reaction with the first radically
transferable atom or group, resulting in the addition of the
coupling compound containing the .alpha.,.alpha.-disubstituted
olefin group at the site of the first radically transferable atom
or group and an elimination reaction comprising the radically
transferable atom or group to form a reactive double bond, and
allowing a second polymer having a second radically transferable
atom or group in the presence of the transition metal complex to
add to the reactive double bond. The molar ratio of the total of
the first polymer and the second polymer to the coupling compound
may be optionally controlled to form a third polymer of a
configuration of at least one of linear, star, graft, and chain
extended materials containing a residue of the first polymer and
the second polymer. The coupling compound may contain one
.alpha.,.alpha.-disubstituted olefin group, and the first polymer
and second polymer may have one radically transferable atom or
group. The molar ratio of the total moles of the first polymer and
the second polymer to the moles of the coupling compound in that
case is essentially 1:0.5. The coupling compound may contain two
.alpha.,.alpha.-disubstituted olefin groups and the first polymer
and second polymer may each have one radically transferable atom or
group and the third polymer is a star polymer with fur arms or the
first and second polymer may have two radically transferable atoms
or groups resulting in one of an extended chain or coupled polymer
with the .alpha.,.alpha.-disubstituted olefin group within the
chain. The coupling compound may be a compact molecule that
contains three .alpha.,.alpha.-disubstituted olefin groups wherein
the molar ratio can be controlled to form a star copolymer with up
to six arms.
[0023] The present invention also includes an .alpha.-substituted
olefin, possessing an exo-double bond, suitable for use as a
macromonomer, in which the .alpha.-substituant is a free radically
(co)polymerized oligo/polymer with a molecular weight greater than
250 possessing a known group at the other terminus of the polymer.
Alternatively, the present invention includes an
.alpha.,.beta.-disubstituted olefin in which each substituant is a
free radically (co)polymerized oligo/polymer with a molecular
weight greater than 250.
[0024] The present invention can provide a graft copolymer when the
coupling compound comprises a backbone polymer with
.alpha.,.alpha.-disubstituted olefin groups as substituents and
forms a grafted polymer wherein the grafts are attached to the
backbone polymer within the graft copolymer chain. The backbone
polymer is preferably produced by an addition or condensation
polymerization process. The backbone polymer is preferably a
polyolefin, and most preferably one of polystyrene, polyethylene,
polypropylene, polyisobutylene, polybutadiene or polyisoprene and
copolymers thereof.
[0025] The present invention further includes a macromonomer
comprising a functional group containing a terminal exo-olefin
double bond derived from free radically (co)polymerizable monomers,
a stereochemistry and tacticity of a material formed by a free
radical polymerization process, and a symmetrical single peak
molecular weight distribution less than 1.5. The macromonomer
preferably has a functionality greater than 90 mole %.
[0026] The present invention may also be extended to a controlled
suspension or emulsion polymerization process comprising
polymerizing free radically (co)polymerizable monomers in the
presence of a system initially comprising a suspending medium, a
surfactant, an initiator having a radically transferable atom or
group, and a transition metal complex which may be a picolyl amine
and participates in a reversible redox cycle with at least one of
the initiator and a compound having a radically transferable atom
or group, wherein the redox conjugate of the catalyst transition
metal is added to the suspending medium. The hydrophobicity and
hydrophylicity of the transition metal complex may be controlled by
the choice of the attached ligands. The polymerization may be
initiated by the decomposition of a standard radical initiator.
[0027] An emulsion controlled radical polymerization process is
provided by the present invention. This process comprises a free
radical initiator, wherein a polymerization is initiated by the
decomposition of the free radical initiator; and a transition metal
compound in a higher oxidation state comprising a radically
transferable atom or group, wherein the radically transferable
group transfers to the residue of the free radical initiator to
form a second initiator, and a third initiator having a radically
transferable atom or group. The process may further comprise adding
a second free radically (co)polymerizable monomer and adding at
least one of the transition metal complex, the transition metal,
the transition metal redox conjugate, a second radically
transferable atom or group, and the counterion.
[0028] A controlled radical polymerization process provided by the
present invention comprises using an initiator attached to a solid
surface, and may further comprise using a free radically
(co)polymerizable monomer and a deactivator, a redox conjugate of a
transition metal complex or a stable free radical. The initiator is
preferably attached to a solid surface. The process catalyst may
comprise a transition metal salt and the system may further
comprise at least one of a persistent free radical, the redox
conjugate of the transition metal catalyst, a stable free radical
or another deactivator. The process persistent free radical is
preferably greater than 1% of the controlled polymerization system
and the monomer. The persistent free radical is more preferably
greater than 3% of the controlled polymerization system and the
monomer.
[0029] The invention provides another embodiment wherein the
controlled polymerization process comprises using an unsaturated
monomer having an attached polyhedral oligomeric silsesquioxane
group t form a polymer. The unsaturated monomer is preferably a
vinyl aromatic or a (meth)acrylate. The polymer formed may be a
homopolymer, a copolymer, a block copolymer, or a star block
polymer.
[0030] The invention further provides a homo-telechelic copolymer
comprising a polymer synthesized from free radically
copolymerizable monomers having a first terminal end and a second
terminal end, a first functional group attached to said first
terminal end, a second functional group attached to said second
terminal end, wherein selection of the other substituents on the
first and second group affords the said second functional group has
a different reactivity than said first functional group.
[0031] The invention further provides a controlled polymerization
process for the production of telefunctional multi-arm star
copolymers. This process comprises polymerizing a free radically
(co)polymerizable monomer in the presence of a system comprising a
telefunctional multi-armed star initiator synthesized from free
radically copolymerizable monomers, a first initiator with one
radically transferable atom or group, and a divinyl compound. The
first initiator may further comprise a second functional group.
[0032] The invention also provides a block copolymer comprising a
block synthesized from vinyl acetate monomers, and a block of free
radically copolymerizable monomers, preferably having functional
end groups. A process for the preparation of block copolymers
comprises polymerizing a first monomer block by a first reaction
mechanism catalyzed by a transition metal, and polymerizing a
second monomer block by a second reaction mechanism catalyzed by
the transition metal, wherein the first reaction mechanism is
different than the second reaction mechanism. The process of
preparing the block copolymer preferably further comprises the
steps of providing a A block synthesized from vinyl acetate
monomers, and a block of free radically copolymerizable monomers
having functional end groups. The functional end group or groups
may be converted into a different group or groups.
[0033] An ABA block copolymer may be formed. It is comprised of two
A blocks synthesized from vinyl acetate monomers, and a B block
synthesized from free radically copolymerizable monomers having
functional end groups. The process of preparing the ABA block
copolymer comprises the steps of providing an ABA block copolymer
having two A blocks synthesized from vinyl acetate monomers and a B
block synthesized from free radically copolymerizable monomers
having functional end groups, and converting the functional end
group into different groups.
[0034] The understanding that the transition metal can contain a
non-radically transferable atom(s) or group(s) as the initial
counterion and that the polymerization proceeds solely through
transfer of the atom or group initially present on the initiator is
the foundation for one of the improvements of the present
invention. Two important improvements in the ATRP process involving
the choice of counterion in the transition metal complex will be
described.
BRIEF DESCRIPTION OF THE FIGURES
[0035] The present invention will be better understood by reference
to the figures.
[0036] FIG. 1. is a graph showing the solvent effect on the removal
of CuBr/PMDETA using DOWEX MSC-1 ion exchange resins.
[0037] FIG. 2. is a graph showing temperature effect on the removal
of CuBr/PMDETA in 50% methyl acrylate/50% chlorobenzene solution
using DOWEX MSC-1 ion exchange resins.
[0038] FIG. 3. is a graph showing Solvent effect on the removal of
CuBr.sub.2/PMDETA using DOWEX MSC-1 ion exchange resins.
[0039] FIG. 4. is a graph showing removal of CuBr/PMDETA using
different types of ion exchange resins.
[0040] FIG. 5. is a graph showing ligand effect on the removal of
CuBr complex using DOWEX MSC-1 ion exchange resins.
[0041] FIG. 6. is a reaction schematic showing coupling through
.alpha.-methylstyrene.
[0042] FIG. 7. is a reaction schematic showing preparation of four
armed star by coupling.
[0043] FIG. 8. is a reaction schematic of the Stober process toward
functional silica particles.
[0044] FIG. 9. is a reaction schematic of surfactant assisted
particle synthesis.
[0045] FIG. 10. is a graph showing kinetic plot for the bulk
polymerization of styrene in Example 1.
[0046] FIG. 11. is a graph showing dependence of molecular weights
and polydispersities on monomer conversion for the bulk
polymerization of styrene in Example 1.
[0047] FIG. 12. is a graph showing kinetic plot for the solution
polymerization of MMA (50% o-xylene, v/v) in Example 2.
[0048] FIG. 13. is a graph showing dependence of molecular weights
and polydispersities on monomer conversion for the solution
polymerization of MMA in Example 2.
[0049] FIG. 14. is a graph showing kinetic plot for the bulk
polymerization of methyl acrylate in Example 3.
[0050] FIG. 15. is a graph showing dependence of molecular weights
and polydispersities on monomer conversion for the bulk
polymerization of methyl acrylate in Example 3.
[0051] FIG. 16. is a graph showing time dependence of conversion
and logarithmic conversion for "reverse" ATRP of MMA.
[0052] FIG. 17. is a graph showing dependence of M.sub.n and
M.sub.w/M.sub.n on the monomer conversion in "reverse" ATRP of
MMA.
[0053] FIG. 18. is a graph showing M.sub.n vs. conversion, for
different ratios MnCl.sub.2/TBAC.
DETAILED DESCRIPTION OF THE INVENTION
[0054] Without limiting the applicability of the use of transition
metal salts as catalysts for controlled polymerization of free
radically (co)polymerizable monomers in any way, the utility will
be explained by initially discussing iron based systems. Up to now,
the ligands used for iron-based ATRP catalysts have preferably been
selected from the classes of phosphines (for example,
tributylphosphine and triphenylphosphine), aliphatic amines (for
example, tributylamine and trioctylamine), substituted bipyridines
(for example, 4,4'-dinonyl-2,2'-bipyridine, dNbpy), tetradentate
Schiff bases, or carbon monoxide and cyclopentadienyl. The iron
complexes with the aforementioned ligands preferably display either
tetrahedral (for example, triphenylphosphine and tributylamine) or
square-planar (tetradentate Schiff base) configurations. See
Matyjaszewski, K.; Wei, M.; Xia, J.; McDermott, N. E.,
Macromolecules, vol. 30, p. 8161 (1997); Moineau, G.; Dubois, P.;
Jerome, R.; Senninger, T.; Teyssie, P., Macromolecules, vol. 31, p.
545 (1998). Wolfe, P. S.; Nguyen, S. T., Am. Chem. Soc., Polym.
Prepr., vol. 39(2), p. 552 (1998). Kamigaito, M.; Sawamoto, M., Am.
Chem. Soc., Polym. Prepr., vol. 40(2), p. 325 (1999). Kotani, Y.;
Kamigaito, M.; Sawamoto, M., Am. Chem. Soc., Polym. Prepr., vol.
40(2), p. 468 (1999).
[0055] Based on the understanding of the structure of the iron
based catalyst, the structure and/or composition of the catalyst
suitable for the process has now been developed further. The
present invention provides a new class of transition metal
complexes and transition metal mediated controlled polymerization
with less than four added components. Catalysts can be formed when
a transition metal is in the presence of a salt where the anion of
the salt interacts with the transition metal to form a new
transition metal compound. Not to be limited by the following
description, an example is a catalyst that is formed by mixing
FeCl.sub.2 with a salt comprising halide anions, with bulky organic
counterions, such as tetrabutyl ammonium chloride, forming
FeCl.sub.3.sup.- NBu.sub.4.sup.+. Additionally the complex
FeCl.sub.3.sup.- NEt.sub.4.sup.+, formed from FeCl.sub.3 and
NEt.sub.4Cl can be used in reverse ATRP. ATRP also can be conducted
using iron catalysts supported on anion exchange resins.
[0056] In this embodiment, particularly suitable for controlled
polymerization of certain monomers with a novel expanded range of
transition metal complexes, the functions of both the initial
counterion on the transition metal and the ligand are superseded by
the use of a transition metal salt containing a soluble charged
counterion. This invention has also been extended to a "reverse"
ATRP reaction. The utility of this novel class of catalysts is
exemplified by a description of conditions for conducting the
reaction with an iron based salt as catalyst for the polymerization
of styrenes, acrylates and methacrylates. While not being limited
to a single class of transition metal salts or a single mechanism,
it is believed that the salts interact with the transition metal in
such a manner that the anionic component of the salt contacts the
transition metal to form a negatively charged transition metal and
a positively charged salt fragment. When the salt is a halide
anion, the halide anions are clearly present as counterions in the
isolated salts but could act as "bifunctional" molecules in
solution with the halide anion fulfilling the role of ligand in the
"classic" ATRP catalyst. Such species have now been demonstrated to
be active catalysts for ATRP.
[0057] The use of complex organic counterions such as tributyl
ammonium or trialkylphosphonium anions permits the use of iron as
the transition metal catalyst to be extended to the controlled
(co)polymerization of acrylates. The present invention achieves a
controlled polymerization process with only three identifiable
added components, (i) an initiator, or polymer chain originator
added or prepared in situ; with one or more radically transferable
atom(s) or group(s); (ii) a transition metal and (iii) associated
counterions comprising a salt capable of copolymerizing added free
radically (co)polymerizable monomers.
[0058] Tetrahedral complexes of iron can be used as catalysts for
ATRP. Such iron complexes with halide anions as ligands have been
known for many years. (See, Gill, N. S., J. Chem. Soc., 3512
(1961); Clausen, C. A.; Good, M. L., Inorg. Chem., vol. 9, 220
(1970); Sproul, G. D.; Stucky, G. D., Inorg. Chem., vol. 11, 1647
(1972). Dunbar, K. R.; Quillevere, A., Angew. Chem. Int. Ed. Engl.,
vol. 32, 293 (1993)). They are negatively charged and are usually
accompanied by bulky organic or arsenic based onium counterions.
The structures of such complexes described in the literature are
shown below and in most cases they are formed by the direct
reaction of onium halides with iron halides in solution. These
complexes have been studied and the present inventors have found
that halide anions with bulky organic counterions (for example,
tetrabutylammonium, tetrabutylphosphonium, tetraalkylarsonium etc.)
are especially preferable as ATRP catalysts. Inorganic counterions,
such as K, Na, Mg etc., may also be employed. 1
[0059] Complexes 1 and 3, (Scheme 1) have been isolated for both
chlorine and bromine, while 2 is known only for X.dbd.Cl. It is
also worth mentioning that, unlike chlorine-based complexes,
mononuclear iron(III) complexes with more than four bromine atoms
have not been isolated, presumably due to their lower stability.
Complex 1 is very likely the active species involved in the direct
ATRP process described below. Complex 2 may be present at onium
salt/FeBr.sub.2 ratios lower than 2. By abstracting the halogen
atom from the initiator or the polymeric "dormant" species,
[FeBr.sub.4].sup.2- complex is converted to a [FeBr.sub.5].sup.2-
species. Although [FeBr.sub.5].sup.2- has not been isolated, it
could be present in solution. The formation of the
[FeBr.sub.5].sup.2- complex anion is supported by the "reverse"
ATRP experiments, which are discussed in Examples 4a -4c, the first
stage of which is shown diagrammatically in Scheme 2. 2
[0060] In the "reverse" ATRP with transition metal salts different
complexes may be involved depending on the counterion/FeBr.sub.3
ratio, as suggested by the variable polydispersities obtained for
different salt/FeBr.sub.3 ratios. The lower polydispersities
obtained for salt/iron ratios higher than 2 suggest the involvement
of [FeBr.sub.5].sup.2- complex, which may allow for an easier
abstraction of a bromine atom due to its lower stability, and
therefore a faster deactivation. In this case, the resulting
[FeBr.sub.4].sup.2- complex could be responsible for the activation
step.
[0061] The ionic nature of transition metal salt complexes when
used as catalysts in the polymerization allows for an easy removal
of the catalyst by simply washing with water the final reaction
mixture. This procedure was tested for the case of styrene
polymerization through direct ATRP and with methylmethacrylate
(MMA) polymerization by the "reverse" approach.
[0062] In the above discussion the halide anion has been depicted
as a bromine atom, but other halides and mixed halide systems can
be used. Different halide counterions can initially be present on
the transition metal and onium salt to form a mixed halide complex.
In addition as taught in other applications mixed halide systems
can be used to control the rate of initiation and rate of
propagation by choosing appropriate initial halide atoms on the
transition metal and initiator molecule.
[0063] The examples detailed later clearly show that ionic iron
complexes with halide anions as ligands associated with cations can
be now be used to control the polymerization of styrene and
(meth)acrylates by both direct and "reverse" ATRP. In the direct
approach, iron (II) bromide complexed with either chloride, bromide
or iodide onium salts allowed for the preparation of polymers with
predetermined molecular weights and low polydispersities. However,
styrene and acrylate polymerizations were initially slow, while for
MMA it was quite fast.
[0064] The "reverse" ATRP process was successfully applied to MMA.
The molecular weights increased with conversion, and they were
close to the values calculated based on the initial monomer/AIBN
ratio. Methyl acrylate displayed the same slow polymerization rate
as in the case of the initial direct approach, while for styrene
the mechanism for the polymerization process changed and the
occurrence of a cationic process led to uncontrolled molecular
weights and high polydispersities. Depending on the onium
salt/FeBr.sub.3 ratio, different iron complexes may be involved in
the polymerization.
[0065] The formation of some polyiron complexes with a lower
reactivity during the polymerization can be an explanation for the
slower reaction rate. If this premise were true then they could be
destroyed by the addition of a complexing agent. The rate of
polymerization for styrene systems was increased by the addition of
Bu.sub.3P.
[0066] The transition metal complex salts disclosed above have also
been shown to be more tolerant of functional groups on the
initiator and (co)monomer(s) than the catalyst systems discussed in
earlier applications. These transition metal complex salts catalyst
systems can initiate polymerization from initiators containing free
carboxylic acid groups and further can incorporate materials
containing a "free" carboxylic acid into the controlled
polymerization process. This is a significant extension of the
capabilities of ATRP since many applications for acrylate based
coating materials or adhesives utilize monomers bearing "free"
carboxylic acids as functional groups to modify the interaction of
the film forming polymer with organic or inorganic substrates.
[0067] The transition metal salts used in ATRP are preferably iron
based salts. Other metals, including copper, nickel, manganese and
chromium were screened and found to be also active for the
initiation of polymerization. However, they appear to offer less
control over the deactivation step leading to polymers with broad
molecular weight distribution.
[0068] In another embodiment related to counterion selection for
process control, the transition metal is held in close conjunction
with, or attached to a solid support. "Attached" as used herein
means physically, physicochemically or chemically bound to the
surface of a solid support through ionic bonding, physisorption,
chemisorption, Van der Waals' forces, coordinate or covalent
bonding and in essence, held separate from the polymerizing phase.
In one particular embodiment, the catalyst is attached to a solid
support through interaction with a counterion that is directly
attached to the support. This embodiment allows the polymerization
to be carried out in an essentially transition metal free
environment which greatly simplifies the production of a catalyst
free product. Preferably, the transition metal itself is supported
directly on either the solid support or the solid ion exchange
resin; and more preferably, the transition metal catalyst is
supported directly on the solid ion exchange resin; and most
preferably, the transition metal catalyst and counterion are
supported on the solid ion exchange resin. In an even more
preferred embodiment, the transition metal is closely associated
with the solid ion exchange resin through one or more shared
counterions that are in turn supported on the solid ion exchange
resin. In this embodiment, the solid ion exchange resin is believed
to function as one of the counterions for the transition metal
compound.
[0069] The concentration of the transition metal, transition metal
catalyst, or counterion is not particularly limited, as long as it
is active in the polymerization according to the invention.
[0070] The ratio of catalyst or supported catalyst is not
particularly limited as long as it is active in the polymerization
according to the invention. This may require that the catalyst be
active in the polymerization medium while interacting with the
support solid. The activity and interaction are balanced by
consideration of all process parameters.
[0071] The ion exchange resin may be any resin or solid support
known to those of ordinary skill in the art and may include without
limitation, organic solids (including organic resins,
functionalized organic resins, acrylic resins, styrenic resins and
phenolic resins), inorganic solids, functionalized inorganic
solids, synthetic and natural zeolites, silicates, clays, aerogels,
xerogels, aluminosilicates, micro- meso- and macroporous materials,
metal oxides, carbonaceous, kieselguhr, aluminas, pumice, activates
carbon, and silica carbides. The ion exchange resin or support may
be in the form of a bead, particle, foam, membrane, paper or fiber.
Preferably, the ion exchange resin may be any of the organic
resins, functionalized organic resins, acrylic resins, styrenic
resins, and phenolic resins. Likewise the method of loading, use
and regeneration of ion exchange resins and solid supports are not
particularly limiting. Various suitable ion exchange resins and
solid catalytic supports and methods of loading and use and
regeneration are described in, e.g. Kirk-Othmer Encyclopedia of
Chemical Technology 4.sup.th ed., (1993), and particularly pages
321-460 in volume 5, and pages 737-783 in volume 14, the entire
contents of which are hereby incorporated by reference.
[0072] The concentration of redox conjugate in solution is not
particularly limited as long as it is active in the polymerization
according to the invention. In a batch polymerization system, it is
preferred that the redox conjugate be present at the start of the
polymerization process.
[0073] The present methods are applicable to the full expanded
range of radically (co)polymerizable monomers that may be produced
by both ATRP and "reverse" ATRP.
[0074] The present invention permits the catalyst to be used in a
fixed or fluid bed reactor when immobilized by or attached (as
previously defined) through interaction of the catalyst complex
with the counterion attached to an ion exchange resin or another
solid support.
[0075] In U.S. Pat. No. 5,807,937, the removal of the catalyst from
the polymerized system by exposure of the catalyst to an absorbing
solid including alumina, silica and/or clay was described. The
significant role of additional control over each of the specific
components of the ATRP process was explored in U.S. patent
application Ser. No. 09/018,554. Heretofore, improvements in
catalyst removal through selective precipitation of the catalyst,
or the polymer while the catalyst was retained in solution, was
described by consideration of the role of the ligand present on the
catalyst. The additional control over the specific components of
the process, such as ligand interaction with solvent, further
specified in U.S. patent application Ser. No. 09/018,554 also
affected the efficiency with which the transition metal complex can
be removed from the system. The importance of the other process
parameters in determining the best conditions for polymerization of
a specific selection of (co)monomers is provided in this
application. The process parameters are also valuable for
optimizing catalyst support, catalyst removal, recycle or reuse.
The range of materials that have been demonstrated to absorb,
adsorb or interact with the complete catalyst complex has now been
expanded to include ion exchange resins and it has been determined
that the rate of removal of the catalyst is dependent on the
polarity of the solvent, the temperature, type of ion exchange
resin, the ionic character and size of the metal complex. By
attention to these variables, as discussed herein, it is possible
to run a controlled polymerization using a catalyst attached (as
previously defined) to, or interacting with a support. The same
considerations regarding the process parameters may be used to
remove the transition metal complex and its redox conjugate from
the polymerization system relatively quickly. In the case of ion
exchange resins, it is believed that this occurs by replacing one
of the counterion(s) initially present on the transition metal
complex by the ion exchange resin. This also offers an expedient
method for catalyst recycle by replacing the first counterion by a
bound or attached counterion and subsequent release of the
transition metal complex from the ion exchange resin by further
treatment with "unbound or free" counterion replacement.
[0076] The removal of active ATRP catalysts by exposure to an ion
exchange media with acidic counterions was studied by examining the
role that different ligands, considering both activator and
deactivator redox conjugate oxidation states, had on the ability of
ion exchange resins to remove the transition metal complex, as
active complexes, from solution. For example, the removal of cupric
and/or cuprous halide complexed by bidentate, tridentate or
tetradentate nitrogen based ligands was demonstrated by contacting
the solution with acidic ion exchange resins. The efficiency of the
removal of the copper was followed by measuring the rate of
decolorization of the system and/or by the release of the
counterion into the system. 3
[0077] bpy is used herein to mean 2,2-bipyridine PMDETA is used
herein to mean N,N,N',N",N'"-pentamethyldiethylene-triamine
Me.sub.6TREN is used herein to mean
tris[(dimethylamino)ethyl]amine
[0078] Scheme 3. Counterion exchange with supported counterion.
[0079] Additionally, for Cu(II) complexes, the amount of Br.sup.-
released is dependent on the ligand used. Indeed, the position of
the equilibrium set up between the transition metal catalyst
(copper) in solution and strongly interacting with the solid
support media was shown to be dependent on the polarity of the
medium, ionic character of the exchanging complex, pH of the
solution, the degree of crosslinking present in the exchange media
or swellability/permeability of the exchange media, acid strength
of the supported counterion and gross size of the ion exchange
resins in addition to the size of the transition metal complex.
Attention to these variables is important for optimum results both
for conducting an ATRP reaction with an ion exchange resin as
counterion and for successful removal of the catalyst for recycle
by an ion exchange system.
[0080] At pH values lower than 3, protonation of the ligand can
occur causing decomposition of the transition metal complex.
[0081] Suitable ion exchange resins include most commercially
available cationic exchange resins containing a sulphonyl anionic
counterion.
[0082] Exchange is faster with a H+ cation.
[0083] Exchange is not strongly dependent on solvent when a large
excess of cation sites are available.
[0084] The rate increased with solvent polarity at lower relative
ratios of total transition metal to available sites.
[0085] FIGS. 1 through 5, discussed in detail in the Experimental
Section herein, show the rate of removal of the catalyst as solvent
polarity, temperature, oxidation state of the transition metal,
different ion exchange resins and different ligands are
considered.
[0086] The experiments detailed in the Experimental Section
demonstrate an efficient method for the removal of the transition
metal complex, exemplified by Cu(I) and Cu(II) complexes, from an
ATRP reaction using ion exchange resins with acidic groups. These
resins can be employed to remove catalysts from bulk
polymerization, organic and inorganic solutions, in addition to
suspension and emulsion systems.
[0087] The resins have removed catalyst from ATRP biphasic
water-borne polymerizations without coagulation of the polymer
latex. It was found that the rate of removal of the catalyst
complexes is dependent on the solvent polarity, temperature, type
of ion exchange resins used and ionic character and size of the
copper complex. In the limiting case of using large excess of
H.sup.+ sites on the resins, both redox conjugate states of the
transition metal complexes can be removed from reaction mixtures
relatively fast.
[0088] The catalyst can be released from the resin by washing the
resin with an acid solution containing a strong acid counterion
such as a hydrogen halide.
[0089] With these tools available to the process engineer, it will
be possible to design a catalyst package that both conducts the
polymerization and is amenable to removal, recycle and reuse
through use of solids discussed in U.S. Pat. No. 5,807,937 with
which the catalyst interacts, and now in particular, ion exchange
resins.
[0090] Another approach to catalyst recycle would be precipitation
polymerization. The polymerization is conducted in a solvent, which
dissolves the polymer at the polymerization temperature, but the
polymer precipitates out at room temperature (or below). The
polymer is recovered by filtration, and the filtrate with the
catalyst dissolved therein is recycled.
[0091] Methanol and absolute ethanol were used as solvents for the
ATRP of MMA, as expected, the reaction mixture was homogeneous at
90.degree. C., but after cooling the non-agitated solution to room
temperature the polymer precipitated as lump, which made it
difficult to recover as a pure material although the bulk of the
catalyst remained in solution. Also, ethanol had swelled the
polymer to some degree. The polydispersity was larger than desired,
indicating some question on the absolute level of control during
polymerization. The less polar solvent, ethanol, afforded a lower
polydispersity.
[0092] A non-polar solvent, heptane was also examined, and while
the polymer again precipitated out of the non-agitated
polymerization during the polymerization as a lump the molecular
weight distribution was 1.21 indicating a certain degree of
control.
[0093] Earlier work disclosed in U.S. patent application Ser. No.
09/018,554, described and demonstrated the concept of designing
functionality into polymers by conducting additional chemistry on a
polymeric material containing one or more radically transferable
atoms or groups. Two extensions of atom transfer processes were
specifically introduced. The extensions could be conveniently
applied at the end of an active atom transfer polymerization
reaction or to any materials containing a radically transferable
atom or group. All materials produced through the ATRP process
contain such a group unless steps have been taken to transform it
into another desired functional group. One concept introduced and
described in U.S. patent application Ser. No. 09/018,554, was
coupling of a polymer containing a radically transferable atom or
group through reaction with a stoichiometric amount of a transition
metal compound, optionally, partially in the zero oxidation state.
Another was utilization of a catalytic atom transfer radical
addition reaction at the end of a catalytic atom transfer
polymerization process to introduce another functional group to the
termini of the polymer.
[0094] Practice of the first polymer coupling process would produce
homo-telechelic materials with the same functional group present at
each polymer terminus while the second terminal functional group
addition process could produce either homo-, "homo"-, or
hetero-telechelic materials. The term "homo"-telechelic will be
employed in this application to describe molecules in which the
same functional group can be attached to atoms containing different
substituents and hence each polymer chain end could react at
different rates in subsequent condensation or crosslinking
reactions. Such behavior would be desirable for example in adhesive
applications where partial reaction, under one set of stimuli could
yield a tacky product for contact adhesion and full reaction, under
a second stimuli would yield a structural adhesive joint. Another
instance would be the controlled build up of molecular weight in
compounding operations whereby the build up of viscosity and hence
intensity of mixing would be predictable.
[0095] The present invention provides flurther examples of and
defines improvements in these processes. The utility of the
improvements is exemplified by preparation of novel building blocks
for subsequent material forming reactions. A novel catalytic atom
transfer coupling process is described based on a greater
understanding and a combination of the chemistry involved in both
the polymer coupling and terminal functional group addition
processes.
[0096] One aspect of the present invention describes the addition
of a non-polymerizable monomer, such as an
.alpha.,.alpha.-disubstituted olefin, to the later stages of an
ATRP reaction and how an understanding, and extension, of the
chemistry that can occur after the addition of this monomer to the
polymer chain can lead to a novel catalytic coupling process. This
specific improvement can be viewed as an extension of the teaching
of introducing functionality through an atom transfer radical
addition reaction and can be exemplified by a discussion of the
chemistry that can occur after the addition of an .alpha.-methyl
styrene unit at the end of a controlled polymerization process
utilizing a bromine as the radically transferable atom or group. It
should be stressed however that the following specific descriptions
of the theory behind the individual steps of this novel catalytic
atom transfer coupling process using various appropriately
isopropenyl substituted benzene molecules are purely illustrative
of the chemistry and are not meant to put any limitation on the
structure of the .alpha.,.alpha.-disubstituted olefin or on the
topology or compositional variations attainable from such coupled
polymeric materials.
[0097] The inventors have determined that the fluctionality that is
ultimately present on a telechelic polymer and the topology of the
material formed by addition of an .alpha.,.alpha.-disubstituted
olefin to an active ATRP process initiated by an initiator
containing one radically transferable atom or group is dependent on
the following factors: (i) the molar ratio of the
.alpha.,.alpha.-disubstituted olefin that is added to the reaction
and the radically transferable atom or group present on the active
growing chain end of the functionally-terminated polymer, (ii)
whether there is one or more chain ends bearing a radically
transferable atom or group, and (iii) whether the molecule
containing the .alpha.,.alpha.-disubstituted olefin comprises one
or more .alpha.,.alpha.-disubstituted olefin units.
[0098] FIG. 6 schematically illustrates the chemistry that takes
place at each active functional radically transferable atom or
group after the addition of an .alpha.,.alpha.-disubstituted
olefin. The .alpha.,.alpha.-disubstituted olefin is represented by
an .alpha.-methyl styrene unit.
[0099] In FIG. 6, starting with a bromo-terminated polymer the
first step of the coupling process is shown as a transition metal
complex mediated redox atom transfer addition reaction. In this
addition reaction, one .alpha.-methyl styrene unit is incorporated
onto the end of a polymer chain. The new .alpha.-methylstyryl
radical end group is formed by addition of the .alpha.-methyl
styrene monomer to an oligomer or polymer radical chain end. When
the .alpha.-methylstyryl radical end group receives the initially
transferred radically transferable atom or group back from the
transition metal complex in the "reverse" redox reaction, a new
polymer end group, containing an .alpha.-methyl-, an .alpha.-phenyl
and an .alpha.-bromo-group, is formed. This type of end group,
containing an .alpha.-substituant, an .alpha.-bromo-group and a
.beta.-hydrogen, can lose hydrogen bromide, preferentially forming,
the kinetically favored new functional exo-olefinic bond. A similar
kinetically favored exo-olefinic bond is formed when
hydrogenhalides are "lost" from methacrylate end groups. Note that
publication WO 99/54365 indicates that the thermodynamically
favored, unreactive endo-double bond is formed in such a reaction.
We have found however that if a molar excess of .alpha.-methyl
styrene has been added to the process, this first stage of the
coupling process exemplifies an atom transfer addition reaction,
and the material can be isolated, affording a functional
hetero-telechelic polymer that can be considered as a macromonomer
suitable for the preparation of graft copolymers by
(co)polymerization through the reactive terminal exo-olefinic
bond.
[0100] However, if less than, or a stoichiometric amount of
.alpha.-methylstyrene is added to the reaction and this newly
formed, kinetically favored, terminally unsaturated functional
polymer is further exposed in situ to the action of the redox
active transition metal compound on a second polymer chain also
containing a terminal radically transferable atom or group, the
formation of a second free radically active chain end can result in
addition of the first formed polymer possessing a reactive
unsaturated exo-bond this first formed polymer adds to the second
active chain end; resulting in a catalytic atom transfer chain
coupling reaction, or an atom transfer linking reaction (ATLR),
with the formation of a new homo-telechelic polymer possessing an
.alpha.-bromo-phenyl group within the polymer chain. If this
coupled polymer loses a second hydrogen bromide group it forms a
halogen free homo-telechelic polymer with an endo-olefinic bond
within the polymer chain. Polymers possessing such endo-olefinic
bonds are less active as macromonomers in ATRP reactions and such
materials are stable under reaction conditions and easily isolated
without gelation of the product.
[0101] The result of this specific exemplary series of controlled
catalytic radical transfer addition reactions and hydrogenhalide
elimination reactions, is a catalytic coupling reaction forming an
.alpha.,.beta.-disubstituted styrene wherein each substituant is
the first formed polymer.
[0102] While this ATLR process has been described and exemplified
by consideration of a mono-functional halo-telechelic polymer with
.alpha.-methylstyrene it can be applied to any oligo/polymer with a
radically transferable atom or group and any linking molecule that
will form a reactive exo-olefinic bond after an ATRA reaction and
loss of hydrogen halide.
[0103] In the above example, if the first formed polymer had been
designed using an initiator with two radically transferable atoms
of groups then the catalytic coupling reaction would take place at
each termini of the polymer and the reaction would be a catalytic
atom transfer chain extension reaction.
[0104] In FIG. 7, the potential of this reaction and its
applicability to the preparation of novel polymers is illustrated
by the example of a di-isopropenyl benzene as the coupling agent.
In the appropriate mole ratio, the use of di-isopropenyl benzene
which results in a sequence of atom transfer addition reactions and
dehydrohalogenation reactions, can culminate in the preparation of
a four armed star polymer, with arms of controlled molecular
weight, composition and functionality, with a residual
disubstituted benzene core.
[0105] Use of triisopropenyl benzene, under appropriate conditions,
would result in a halogen free six armed star polymer with
functional end groups.
[0106] Further defining the capabilities of this reaction to
prepare novel materials, if one employs, for example, a (co)polymer
with .alpha.-methylstyryl, or isopropenyl benzene substituents
along the chain as the linking molecule for this catalytic coupling
reaction then one would prepare graft copolymers with the
possibility of two similar graft (co)polymers emanating from one
specific site on a polymer backbone. This would be a new type of
graft copolymer for copolymers with grafts composed of free
radically (co)polymerizable monomers. The new graft copolymer is
one in which the polymers are grafted to each other within both
polymer chains rather than grafting to the backbone polymer at the
terminus of the other polymer chain. Indeed there would be a
further degree of symmetry in these "grafted within" copolymers
since the grafting site would essentially be situated at the
midpoint of the grafted chain. "Grafting within" two polymer chains
results in differences in the development of bulk properties in
materials, particularly elastomeric materials, and in differences
in various interfacial and diffusion properties. The differences in
the interfacial and diffusion properties occurs for the bulk graft
copolymer, for property development in composites, and blends or
alloys containing such a graft copolymer as a component or as a
polymeric surfactant, and for surface property modification or
interfacial property control, particularly when compared to graft
copolymers where grafting occurs at one polymer terminus as is the
case for current commercial graft copolymers. The two polymer
chains particularly suited to "grafting within" include polymer
chains with differing, readily modifiable, composition, differing
phylicities or different macrofunctionalities, and known functional
groups on the grafted polymer chains.
[0107] (Co)polymers with isopropenyl benzene substituents along the
chain need not be considered exotic starting materials since
copolymers of ethylene, propylene and isobutylene are presently
commercially available with benzene substituents present on the
backbone. These units introduced through copolymerization of
ethylene, propylene or isobutylene with (substituted) styrene could
be readily prepared with precursors for isopropenyl substituents,
yielding the potential for novel "grafted within" copolymers from
the largest volume addition polymers in the market. Indeed any
copolymer containing a styrene residue in a monomer unit could be
converted into a backbone polymer suitable for grafting to, or
grafting through, by this purely exemplary disclosed coupling
process resulting in polymers "grafted within" both polymer chains
and such backbone polymers can be prepared by controlled
polymerization processes yielding materials in which all polymer
segments have been assembled utilizing controlled processes.
[0108] Indeed, the system described above can be utilized with any
polymer containing an appropriate .alpha.,.alpha.-disubstituted
olefin functional group attached to the polymer chain. Such
.alpha., .alpha.-disubstituted olefins would include isopropenyl
(meth)acrylate, vinyl ethers, or isopropenyl ethers which can be
derived from allyl ethers. In this later case it would be possible
to copolymerize a vinyl allyl ether with other free radically
copolymerizable monomers by an ATRP process, isomerize the allyl
substituent to an isopropenyl substituent, and use this material as
the linking molecule for a second polymer prepared by an ATRP
process yielding a grafted within polymer in which each segment of
the graft copolymer has been prepared by a fully controlled radical
polymerization process. Since the comonomers for the copolymer
segments can be chosen from any free radically copolymerizable
monomers there is an almost unlimited choice of property
differentiation attainable between the blocks of the graft
copolymer in a simple sequential process.
[0109] If one employed di-isopropenyl benzene as coupling agent at
a concentration of 0.5 molar equivalents to the growing polymer
chain, or radically transferable atoms or groups, then the first
coupled polymer formed would be a statistical mixture of coupled
products retaining a statistical mixture of residual available
.alpha.,.alpha.-substituted unsaturation within the first coupled
polymer chain(s). Further use of this polymer to couple a second
(co)polymer formed from different (co)monomer(s) would result in a
statistical mixture of four armed star polymers.
[0110] However if one desired further control one could employ a
molecule comprising two different .alpha.,.alpha.-disubstituted
olefins, with slightly different reactivities, then the more
reactive .alpha.,.alpha.-disubstituted olefin would react with the
first copolymer forming a coupled copolymer with a second
.alpha.,.alpha.-disubstituted olefin within the coupled polymer
chain. Use of this first coupled (co)polymer to couple a second
(co)polymer would result in a (co)polymer with two arms of one
(co)polymer composition and two arms of another (co)polymer
composition; essentially two polymers mutually grafted at the
middle of each (co)polymer chain. Again such a novel four armed
star material, each arm of which is prepared by a controlled
polymerization from a wide range of radically (co)polymerizable
monomers, and optionally possessing functionality at the end of
each polymer chain, would bring a new set of properties to
surfactants, adhesives, alloying and blending surfactants,
dispersants, personal care products and composite matrix components
as polymer properties such as solubility, phylicity, Tg, and other
properties are tailored for subsequent use or reaction in the
preparation of blends, alloys or composite materials.
[0111] One does not have to prepare two different copolymers in
order to obtain useful properties from such hetero-arm star
(co)polymers. When one initiates the polymerization of one or more
radically (co)polymerizable monomers with one concentration of
initiator and adds a second aliquot of initiator prior to
completion of the first (co)polymerization then a material with a
bimodal molecular weight is obtained. If indeed one was conducting
a copolymerization and the (co)monomers had different reactivity
ratios then the copolymers, initiated at different times in a batch
process, would have different compositions or gradients along the
copolymer chain. Another route to compositional variation would be
to add a second monomer some time after the initiation of
polymerization or at the time of the second addition of initiator
to form in-situ a block/gradient copolymer. Coupling by use of
molar equivalents of .alpha.,.alpha.-disubstituted olefin units
lower than 0.5 forms a multiarmed star with a statistical mixture
of arms of different molecular weight/composition, the star
polymers are a statistical mixture of the compositions and
molecular weights initially present, and the hetero-armed star
(co)polymers are formed in a single coupling step.
[0112] Materials with similar topology have been formed by living
anionic polymerization of styrene and butadiene, where a second
addition of catalyst is made prior to the complete conversion of
the first added styrene monomer, forming block copolymers with
polystyrene segments with different molecular weights. Such
materials are known commercially as Styroflex.RTM. resins when
supplied by BASF. (See, Macromol. Symp., vol. 132, pp. 231-43
(1998); and U.S. Pat. No. 5,910,546 issued to Phillips Petroleum
Company). However, in contrast to the limited choice of monomers
that can be polymerized by an anionic mechanism, with the ATRP
processes described in this application the composition and linear
topology of the arms can be chosen from a wide range of radically
(co)polymerizable monomers and the resulting materials can develop
a much wider range of properties than the commercially available
useful pure styrene or styrene/butadiene copolymers known to
date.
[0113] Since many useful materials can be prepared with "less than
perfect," or statistic coupling of the components of the system,
then desirable products would also be obtained by coupling between
a dispersed particle or surface and a reactive polymer chain end.
If the particle or the surface of the material possessed an
attached functional group additionally comprising a radically
transferable atom or group then the above described coupling
reaction could be conducted to form polymer grafted to the particle
or surface. Such a reaction would modify the particle or surface of
a material and would produce more readily dispersible particles or
blends of materials with stronger interfacial properties.
[0114] An exo-double bond is itself a reactive group and much known
chemistry is available to capitalize on this functional group or to
convert this group into alternate active functionality for further
reactions or interactions including polymerization and
copolymerization. A further degree of functionality would be
introduced to the first head group by conducting an atom transfer
addition reaction with an appropriately substituted
.alpha.-substituted-.alpha.-hydroxymethyl olefin yielding an
aldehyde/enol after dehydrohalogenation has occurred. Examples of
such an olefin include .alpha.-hydroxymethyl styrene,
1-hydroxy-.alpha.-ethyl styrene or ethyl-.alpha.-hydroxy
methylacrylate.
[0115] In the above examples describing the fully controlled
coupling reaction the chemistry has been exemplified using an
.alpha.-methyl substituant on a styrene. Other substituents would
also work equally well, or even better if faster reactions are
desired.
[0116] Use of an aromatic substituant such as that present in
1,1-diphenylethylene or 1,3-bis(1-phenylethenyl) benzene would also
appear to be appropriate for "living" radical coupling. Both
molecules have been demonstrated as suitable coupling agents for
living anionic and "living" cationic coupling. However in the case
of these specific agents, the first formed polymer product of
addition of the appropriate .alpha.,.alpha.-di-aryl substituted
olefin is a molecule with an endo double bond. I.e.
1,1-diphenylethylene essentially caps the polymer chain forming a
polymer with a terminal endo-double bond. This is precisely the
chemistry described in WO 99/54365. However
1,3-bis(1-phenylethenyl) benzene acts to couple two chains by
sequentially capping two different chains. One further available
molecule that would act to link two polymer chains by such
sequential atom transfer capping reactions described above is
2,2-bis[4-(1-phenylethenyl)phenyl]propane.
[0117] In the above examples a single benzene unit has been used as
one substituant on the olefin or as the foundation for the linking
group for multifunctional molecules but other substituents and
other linking groups can be employed.
[0118] Throughout this discussion the focus has been on the
preparation of polymers possessing functional groups of the termini
of the polymer chains. However, for some applications, such as
viscosity index modifiers, star copolymers with no functional
groups would find utility and indeed would be preferred.
[0119] The complete reaction of a non-polymerizable (co)monomer
such as allyl alcohol or 1,2-epoxy -5-hexene with the active
polymer chain end, optionally with a hydroxy group present on the
initiator chain end, is generally a slower reaction than the
polymerization of the monomer. The inventors have found it
convenient to utilize some of the tools demonstrated in earlier
applications to increase the rate of reaction, including the use of
(i) an excess of the allyl alcohol, (ii) the addition of more
catalyst and, (iii) a reduction in the concentration of the redox
conjugate present in the system. These actions arise from a
consideration of the dynamics of the equilibrium between each of
the components of the ATRP process. A high level of functionality
can be introduced into a polymer by following these steps, see the
later Experimental section.
[0120] The "homo" telechelic materials formed in this type of
reaction can be very useful in the formation of adhesives and
sealants through reaction with isocyanate curing agents. The
differences in reactivity between the hydroxy groups on each end of
the polymer allows one to control the curing rate of each polymer
terminus and the resulting properties of the partially cured and
completely cured material.
[0121] True homo-telechelic polymers can also be prepared by use of
this combination of an ATRP process followed by reaction with a
non-polymerizable monomer containing the desired functionality as a
second substituent. One employs an initiator with more than one
radically transferable atom or group. A difunctional initiator
leads to a linear homo-telechelic polymer while use of initiators
with greater numbers of transferable atoms or groups leads to
telechelic star (co)polymers. In a non-limiting example, use of an
initiator such as dimethyl-2,6-dibromohep- tadionate for the
polymerization of methyl acrylate followed by addition of a
hydroxy-containing non-polymerizable monomer leads to a true
homotelechelic .alpha.-.omega.-dihydroxy-poly(methyl acrylate.) As
above, the other components in the process affect the rate of
reaction but under appropriate conditions a dihydroxy polymer
suitable for subsequent material forming reactions such as
conversion into a polyurethane is produced.
[0122] With these teachings available three general techniques can
now be applied for the synthesis of telechelic polymers and will be
exemplified by consideration of the preparation polydiols by atom
transfer radical polymerization and they are shown below in Scheme
4. The first method (A) involves a one-pot technique where the
polymerization of methyl acrylate (MA) was initiated by a
difunctional initiator (Br--I--Br), such as dimethyl
2,6-dibromoheptadionate. An excess of allyl alcohol was added to
the polymerization mixture at high conversion. Allyl alcohol is
able to add to the growing polymer chain. However, the formed
radical is not able to propagate. Instead, it undergoes an
essentially irreversible reaction with cupric bromide yielding a
bromine terminated polymer. The polymer was analyzed before and
after the addition of allyl alcohol. 4
[0123] The degree of functionalization was determined. In the
example given, the degree of functionalization was f=1.9 three
hours after the addition of allyl alcohol.
[0124] The second technique employed involved initiation of methyl
acrylate by a hydroxyl-functionalized initiator, i.e. ethylene
glycol mono(2-bromoisobutyrate), as is shown as route B in Scheme
4. At high conversion, allyl alcohol, copper(0), cuprous bromide
and PMDETA were added. The degree of functionalization was
calculated before the addition of allyl alcohol and 3 hours after
the addition of allyl alcohol. The degree of functionalization just
before the addition of allyl alcohol was f=1.0 corresponding to one
chain per hydroxyl group. This is expected because the only chain
initiating event occurs when the hydroxyl-functionalized initiator
reacts with CuBr yielding a hydroxyl-functionalized radical and
cupric bromide. Three hours after the addition of allyl alcohol the
degree of functionalization was f=1.8.
[0125] The third technique shown in Scheme 4, as route C, involves
coupling of .alpha.-hydroxy-.omega.-bromo-poly(methyl acrylate) by
a coupling agent. This polymer was prepared by initiating methyl
acrylate with ethylene glycol mono(2-bromoisobutyrate). The
polymerization was terminated at 80% conversion, and the polymer
was isolated by precipitation in hexanes. The coupling reaction was
performed by measuring the polymer and cuprous bromide in a
round-bottomed flask. The flask was sealed and purged with
nitrogen. PMDETA, the coupling agent, and benzene were added and
the reaction mixture was placed at 60.degree. C. In the case where
the coupling agent was .alpha.-methylstyrene and the ratio of
chains to .alpha.-methylstyrene was two, the molecular weight
increased from 1330 g/mol to 2960 and the molecular weight
distribution increased from 1.10 to 1.32. The degree of
functionalization as determined by .sup.1H NMR was f=1.8.
[0126] The functionality of the polymers formed by coupling was
demonstrated by formation of a polyurethane by reaction of the
linear .alpha.-.omega.-dihydroxy-polymers with
methylenediisocyanate [MDI].
[0127] When m-diisopropenylbenzene was used as the coupling agent
and the ratio of chains to m-diisopropenylbenzene was four, the
molecular weight increased from 1060 to 3860 and the molecular
weight distribution increased from 1.10 to 1.69. The degree of
functionalization was f=2.8. This result indicates that stars are
formed if the coupling is performed with m-diisopropenylbenzene. If
a 1:1 ratio of chains to m-diisopropenylbenzene was used, analysis
clearly showed that addition of m-diisopropenylbenzene was followed
by elimination of HBr. This led to the suggested mechanism shown in
FIG. 7 where addition of poly(methyl acrylate) to
m-diisopropenylbenzene is followed by reaction with cupric bromide
and subsequent elimination, yielding HBr and a terminal olefin (1).
The newly formed olefin is able to add to poly(methyl acrylate), to
yield (2), which then reacts with cupric bromide and eliminates HBr
to yield the coupled product (3). A similar addition can occur at
the second double bond of the coupling agent and the final product
is a star with up to four arms.
[0128] In example B) of Scheme 4, describing the use of a
bifunctional initiator molecule containing first a radically
transferable atom or group and a second different functional group
then a hetero-telechelic polymer is initially formed. When the
second functional group on the initiator molecule is a hydroxy
group then the initial (co)polymer product contains a hydroxy group
at one chain end and a radically transferable atom or group at the
other chain end(s). The atom transfer catalytic coupling process
described above, C) of Scheme 4 , can lead to a homo-telechelic
.alpha.-.omega.-dihydroxy-polymer, i.e. when 0.5 mole equivalents
of a molecule exemplified by .alpha.-methyl styrene is added, or a
tetra-.omega.-hydroxy star polymer after addition of 0.25 mole
equivalents of a molecule exemplified by a di-isopropenyl benzene
at the desired stage of the atom transfer polymerization step.
[0129] In the above discussion a first hetero-telechelic polymer;
.alpha.-bromo-(.omega.-hydroxy poly(methyl acrylate) was used as an
exemplary model polymer for this atom transfer coupling reaction.
This model polymer was prepared by polymerization of methyl
acrylate using ethylene glycol mono(2-bromoisobutyrate) as
initiator and cuprous
bromide/N,N,N',N",N"-pentamethyldiethylenetriamine (PMDETA) as the
transition metal catalyst. Use of 0.5 mole of .alpha.-methylstyrene
per mole of .alpha.-bromo-.omega.-hydroxy poly(methyl acrylate)
essentially doubled the number average molecular weight (Mn). When
0.25 mole of di-isopropenyl benzene was used in the coupling
reaction, the Mn of the polymer, after removal of bromine, was
quadrupled indicating the formation of a four armed star polymer
with four terminal hydroxy groups.
[0130] The dehydrohalogenation reaction to form either the endo- or
exo-double bond can be base enhanced, or assisted by the addition
of an acid acceptor. Any acid acceptor can be used including
compounds such as a basic organic molecule including linear and
heterocyclic N containing compounds, ion exchange resins and/or
inorganic acid acceptors. In the particular exemplary examples
provided above to demonstrate how this novel coupling reaction can
give increased control over topology and functionality by
application of these reactions it was also determined that the
dehydrohalogenation reaction can be assisted by the addition of
base including an organic base such as triethylarnine or
2,6-di(t-butyl)-pyridine.
[0131] While not limiting the application of the coupling reaction
to the use of an .alpha.-substituted styrene as the linking
molecule, it is clear that any hetero-telechelic molecule
containing a radically transferable atom or group can be
transformed though this catalytic atom transfer coupling reaction
and that the overall level of functionality of the resulting
material can be controlled by selective use of compact molecules
containing mono-, di-, or tri-substituted isopropenyl groups to
form linear, four armed or hexa-armed polymers. When di-, or tri-,
substituted isopropenyl benzene are used and the reaction is run
with higher, but still less than one to one, molar ratio's of the
unsaturated isopropenyl benzene to radically transferable atom or
group, then controlled levels of functionality between 2 and 4 or 2
and 6 can be obtained. Another route to functional linear polymers
with controlled levels of functionality greater than two is to use
mixtures of mono and di-, or tri-, substituted isopropenyl benzene.
Materials with levels of functionality greater than two are a
desired choice when the resulting application for these polymers is
use of these materials in polymeric condensation reactions to form
fully crosslinked systems. The level of crosslink density being
controlled by the degree of functionality first present in the
components of the system.
[0132] One should also consider that the intermediate products, the
exo-olefinic terminated polymers formed when an excess of the
.alpha.,.alpha.-substituted olefin is added, are themselves
multifunctional materials. The .alpha.-methyl styrene discussed
above is one example of an .alpha.-substituted olefin.
[0133] If one desired non-linear thermoplastic polymers with a
multiplicity of polymer chain interactions an extension of the use
of an isopropenyl benzene as a substituant in a (co)polymer to form
graft copolymers wherein the graft copolymer is grafted within the
polymer chain can be employed. A convenient building block is a
copolymer with a m-di-isopropenyl benzene as a substituant in a
(co)polymer. This would lead to a four armed graft copolymer
emanating from each unit initially containing the m-di-isopropenyl
group.
[0134] The above example for the preparation of a linear polymer
used an initiator in which the second functional group present on
the initiator molecule was a hydroxy group and produced polymers
with terminal hydroxy functionality. However, it is known from the
literature that the second functional group can be chosen from many
functional groups and is introduced to an ATRP polymerization by
choosing an appropriate initiator. All normal small organic
functional groups including epoxy, carboxy, amine, silyl,
perfluoro-alkyl, and cyano, can now be introduced into
homo-telechelic polymers by this catalytic coupling process using
appropriate (masked)functional initiators. However, as described in
other applications the initiator can be any molecule containing a
radically transferable atom or group including low molecular weight
inorganic materials and organic/inorganic or hybrid polymers.
Application of this catalytic coupling process can therefor lead to
telechelic symmetrical hybrid polymers, block copolymers and
functional hybrid star copolymers.
[0135] The use of di-isopropenyl benzene to prepare a range of
useful well defined star polymers as described above is a more
controlled process than the use of divinylbenzene as a (co)monomer
to prepare "star polymers" by the "arm first" method, described in
earlier in U.S. patent application Ser. No. 09/018,554. However use
of functional initiators for an ATRP process followed by addition
of divinylbenzene, or other radically (co)polymerizable diolefinic
molecules, to the reaction can lead to end functional star polymers
with a greater numbers of arms than the fully controlled process
described above. End functional star polymers with various
functional groups such as hydroxy, epoxy, amino, cyano, alkyl,
perfluoroalkyl, silyl, siloxane, phosphazene and halogen on the
outer layer chain termini can be successfully prepared by
addressing the pertinent factors, such as choice of counterion,
optional solvent, appropriate concentration of redox conjugate, and
where appropriate added metal zero and if required added ligand,
the structure and molar ratio of added diolefinic molecule to
.omega.-functional linear growing polymer initially terminated with
a radically transferable atom or group.
[0136] Divinylbenzene is shown to be particularly suited for
preparation of "arm first" star polymers containing styrene as a
(co)monomer. The utility of other commercially available diolefinic
coupling agents is also demonstrated for acrylate and methacrylate
containing copolymers. 1,4-Butanediol diacrylate and ethyleneglycol
dimethacrylate have been used to form star polymers with
substituted acrylate and methacrylate (co)monomers. Within the
descriptions of these diolefinic coupling agents as models it is
clear that any difunctional free radically (co)polymerizable
monomer can be chosen as the active (co)monomer for the core of
this type of tele-functional multi-armed star (co)polymer.
[0137] The different coupling agents displayed differences in
reactivity similar to that displayed by the monovinyl model
monomers. Under one set of reaction conditions for evaluation of
the coupling reactions based on coupling of telechelic
t-butylacrylate oligo/polymers with ethyleneglycol dimethacrylate
gave complete gelation of the reaction mixture while use
1,4-butanediol diacrylate and divinylbenzene did not lead to
gelation. Use of 1,4-butanediol diacrylate did lead to formation of
a viscous fluid very quickly. Size exclusion chromatography (SEC)
traces showed that 1,4-butanediol diacrylate coupled core polymers
had undergone significant star-star coupling affording high
molecular weight polymers with broader molecular weight
distributions. In contrast, divinyl benzene led to formation of
single core coupled star polymers with narrow molecular weight
distributions. Continued exposure of these divinyl benzene star
polymers to reaction conditions led to a more tightly coupled
single core polymer rather than core to core coupling. As before,
several factors are pertinent to the reaction including the choice
of exchange halogen, the addition of the appropriate level of redox
conjugate deactivator, the ratio of coupling agent to telechelic
oligo/polymer and the optional use of solvent.
[0138] The coupling chemistries discussed above are shown
diagrammatically in Scheme 5. 5
[0139] The structure of the R linking group in the divinyl compound
can be chosen to reflect the solubility parameters of the first
polymer and/or the desired structure of the star (co)polymer. In
addition it is possible to further modify the structure of the core
by (co)polymerization of the chosen divinyl compound with a monomer
that will further tailor the properties of the core to the
application of the product.
[0140] The properties of the materials prepared by the topological
control described above can also be enhanced by use of functional
initiator for the prior preparation of telechelic functional arms.
Discussing, once again as a non-limiting example, use of an
initiator with a radically transferable atom or group and a hydroxy
group, as a substituent on the polymer originator, allows one to
form multiarm core polymers with hydroxy functionality at the
terminus of each arm. In addition to possessing inherently useful
bulk properties these tele-functional multiarm (co)polymers can
find use as material modifiers since they possess low viscosity,
for ease of dispersion, and high functionality for reactivity with
other materials or for surface modification in blends and alloys.
As an example they would modify the surface properties of fibers,
films or the interfacial properties of blends containing dispersed
solid phase materials and in interfacial property modification
during the preparation of composites.
[0141] Another specific non-limiting example would be initiation of
the (co)polymerization of the linear arms with an initiator
possessing a functional silicone containing group. The resulting
multifunctional multi armed star (co)polymer would be a hybrid
(co)polymer possessing functional inorganic groups at each
accessible polymer terminus. An example of the utility of this type
of hybrid material would be to act as both a material dispersant
and to modify the surface properties of a high performance magnetic
recording media polyester film, another would be in the preparation
of glass or mineral filled materials where the multiple
functionality would find utility in tailoring the interfacial
properties between the matrix and dispersant/reinforcement.
[0142] In addition to tailored telechelicity use of the disclosed
controlled polymerization process combined with the capabilities of
modifying the properties along a polymer chain, the multifunctional
gradient or block star copolymers can possess tailored bulk
properties such as compressibility, allow for efficient dispersion
in any matrix, and hence modification of both compressive and
tensile properties of composite materials.
[0143] As we have demonstrated for well controlled catalytic
coupling of active polymer chains in ATRP there are significant
changes in the polymer topology when one moves from one functional
coupling group to multiple groups. In this "less controlled" system
using simple di-substituted vinyl compounds for coupling, or core
forming reactions, there are also topological changes when one
moves to multi-functional compounds as the matrix material. Use of
such multi-functional reactants produce products that resemble well
defined functional networks rather than stars. Use of this
technique will allow the formation of elastomeric networks in which
the elastic response and hysteresis of the material can be tuned by
consideration of the molecular weights of the low Tg segments and
branching density of the core or linking molecule.
[0144] Miktoarm star (.mu.-star) polymers can be prepared by the
formation of star polymer first through the "arm first" approach,
followed by growing polymers from the crosslinked macroinitiator
core. This has been demonstrated for controlled radically
(co)polymerizable monomers by first using a preformed poly(tBA) arm
as the first macroinitiator for the core forming coupling reaction.
A star poly(tBA) core macroinitiator was produced which was
followed by the formation of .mu.-star when nBA was added and
polymerization was continued. Hydrolysis of the tBA produced a
(.mu.-star) polymers with arms of differing phylicities.
[0145] In the integrated ATRP/ATRA process, the first alkyl halide
end-groups are activated by a transition metal catalyst, to
generate radicals which then react with or add to functional
alkenes that are not capable of homopolymerization under these
conditions. As an example of this approach, stars and hyperbranched
polymers prepared by ATRP are functionalized by the incorporation
of reactive moieties on the activated terminal sites of arms, or
branches, of the polymer. Additionally as described earlier, the
use of a functional initiator allows for the synthesis of polymers
with functionality at the initiator site, along with an alkyl
halide group at the chain end. The synthesis of functional
multi-armed stars can be achieved by two schemes using the ATRP of
free radically (co)polymerizable monomers to produce polymers with
alkyl halide groups at one chain end. With an initiator possessing
a radically transferable atom or group and a second functional
group stars are formed by in the presence of divinylbenzene (DVB)
at the end of the polymerization process. The other approach is to
use an initiator with multiple radically transferable atoms or
groups and conduct an atom transfer radical addition reaction with
a molecule possessing a second functionality at the end of the
polymerization step.
[0146] Schemes 6 and 7 present the synthesis of functional stars
and hyperbranched polymers by ATRA and ATRP reactions. 6 7
[0147] If one wished to form functional star copolymers by the arm
first approach in which the core was essentially free from
radically transferable atoms, then one would carry out the coupling
reactions with isopropenyl substituents rather than
vinyl-substituents as described above for the catalytic atom
transfer coupling reaction.
[0148] One specific tool for control over the ATRP process that was
introduced in U.S. Pat. No. 5,807,937 was the use of the redox
conjugate of the transition metal complex to control the rate of
polymerization and the molecular weight distribution of the polymer
formed. This concept can now be extended, particularly in emulsion
systems to incorporate addition of the transition metal redox
conjugate alone, i.e. without additional complexing ligands, to
further modify the various equilibria associated with use of a
transition metal complex in an active biphasic polymerization
media. This is demonstrated by the addition of cupric bromide to
the aqueous phase of a copper based emulsion ATRP. The presence of
the cupric bromide in the aqueous phase prevents, significantly
reduces, or sufficiently reduces, the migration of the ligand
complexed cupric bromide redox conjugate from the organic phase
into the aqueous phase and hence one retains control over the
polymerization. The critical role of the redox conjugate plays in
determining the controllability of the polymerization is further
detailed by a consideration of the manner in which the transition
metal complex is partitioned within the system by a continuation of
the careful consideration of the effect of substitution in various
ligands
[0149] Conditions for the controlled polymerization of free
radically (co)polymerizable monomers have also been developed for
miniemulsions using a small molecule cosurfactant, U.S. patent
application Ser. No. 09/126,768. Oil soluble standard free radical
initiators, exemplified by AIBN, can be now be utilized in such
systems. A further advance in emulsion systems allows the
polymerization of water soluble monomers by the "standard" ATRP
process. "Free radical initiator" and "standard free radical
initiator" as used herein shall refer to the initiators used in
conventional noncontrolled free radical polymerization to generate
a radical and begin the radical polymerization. Examples include
azo compounds, such as AIBN, peroxide compounds, such as bibenzoyl
peroxide, and other commercially available initiators, such as
V-50. Removal of the catalyst by exposure to ion exchange resins is
particularly expedient in emulsion systems. The increased level of
control that arises from advances in understanding the role of the
ligand in modifying catalyst activity is also demonstrated for
emulsion systems where the rate of polymerization of acrylates is
increased by use of ligands such as a substituted picolyl amine
such as N,N,-bis-(2-pyridylmethyl)octylamine (BPMODA).
[0150] U.S. patent application Ser. No. 09/126,768 disclosed
extension of controlled ATRP to biphasic water-borne systems and
discussed the new challenges to finding an appropriate catalytic
system. To achieve the controlled/"living" feature of the
polymerization, as well as maintain a stable dispersed system,
there were many issues to be considered. For the ligand, at least
two extra requirements had to be considered, the ligand should have
sufficient binding affinity towards the metal in order to compete
with water as a potential ligand; it should also solubilize
sufficient active metal complex, namely both Cu(I) and Cu(II), in
the organic phase where the polymerization takes place, so that the
essential equilibrium for ATRP can be established. Not every ligand
that works in bulk or solution ATRP continues to be successful in
water-borne systems. To find appropriate ligands, several potential
candidates were investigated. The investigation indicated that
greater solubility of the Cu(II) species was critical, and by
increasing the solubility of the bipyridine ligand through
increasing the length of the alkyl substituant greater control was
obtained.
[0151] The results are presented in Table 13 for the polymerization
of butyl methacrylate with various substituted bipyridene
derivatives as ligands. The ligands are shown in Scheme 8. 8
[0152] The use of 4,4',4"-Tris(5-nonyl)-2,2':6',2"-terpyridine
(tNtpy), shown below, a substituted terpyridine also led to
controlled polymerization of BMA. 9
[0153] Similar to the experience with unsubstituted bipyridine, the
use of the aliphatic amines, PMDETA and Me.sub.6TREN, shown below;
failed to give controlled character to the polymerization of BMA in
water-borne system, due to the high solubility of the Cu(II)
complex in water. 10
[0154] Two hybrids of aliphatic and aromatic amines, picolyl
amines, N,N,-bis(2-pyridylmethyl)octylamine (BPMOA) and BPMODA,
were also tested as the ligands for the ATRP water-borne systems.
11
[0155] Again using butyl methacrylate, purely as an exemplary
monomer which in no manner should limit the utility of the
conclusions, the polymerizations using both ligands initially were
not very well controlled. Since these ligands work very well in
bulk and solution polymerization this result in an emulsion system
could be attributed to non-optimal partitioning of the transition
metal system in the multiphase system. With this interpretation of
the "failure" it is expected that adjusting the reaction
conditions, the control of the polymerization of BMA may be largely
improved, especially in the case of BPMODA.
[0156] Indeed, when the two ligands were applied to butyl acrylate,
the control was improved because of the larger partitioning
constants of Cu(II) complexes in butyl acrylate than in butyl
methacrylate. BPMOA, although excellent in bulk polymerization of
butyl acrylate still resulted in the formation of polymers with
polydispersities higher than 1.5 in water-borne system. This
indicates a poor solubility of the deactivator in the organic
phase. Having a longer hydrophobic chain, BPMODA greatly enhances
the organic solubility of Cu(II) species. As a consequence, the
polymerization of butyl acrylate using BPMODA as the ligand was
well controlled, as evidenced by a linear increase of molecular
weight with monomer conversion, as well as polydispersities less
than 1.3 throughout the polymerization. This would indicate that
the phylicity of the catalyst complex is of importance in
determining the level of control attainable from a given system and
that the partition coefficient of the catalyst complex can be
adjusted by consideration of the substituents on the ligand in
addition to consideration of the type of ligand employed.
[0157] Among the several non-limiting ligands investigated,
bipyridene derivatives with long alkyl substituents (dNbpy, dAbpy
and dHDbpy), and BPMODA are good ligands for ATRP water-borne
systems. The partitioning of the corresponding Cu(II) complexes
between organic and aqueous phases, as well as the values of the
atom transfer equilibrium constants, play crucial roles in
controlling the polymerization outcome.
[0158] In U.S. patent application Ser. No. 09/126,768 describing
emulsion ATRP the use of reactive substrates was discussed. In
addition the use macromonomers as surfactants and comonomers has
led to novel compositions for polymeric emulsions. In the area of
surfactants the relative hydrophylicity of the molecule must be
considered. In the polymerization of butyl methacrylate use of a
hydrophylic surfactant leads to polymer coagulation as the
polymerization proceeds. With a surfactant that leads to a stable
emulsion it is possible to produce a stable system at low
surfactant concentrations and the level of surfactant employed does
not affect the polymerization rate or the molecular weight of the
polymer produced. This is an unexpected result since one could
expect a proportional relationship. The effect can be explained if
one assumes that the amount of surfactant affects the partitioning
of the different oxidation states of the metal complex. A higher
level of surfactant could bring more cupric complex into the
organic phase decreasing the polymerization rate hence offsetting
the effect of reducing the particle size or increasing the number
of particles. This indicates that the surfactant can be selected to
produce the desired particle size at an appropriate polymerization
rate.
[0159] The particle size is also affected by the concentration of
Cu(II) added to the system.
[0160] In reverse ATRP emulsion systems, the efficiency of the
added standard free radical initiator is only 30% for AIBN,
although this efficiency can be improved by selection of more polar
initiator molecules. If a conventional ATRP initiator RX is also
added to the system the apparent efficiency of the initiation is
increased to 75%. This is a result of the standard ATRP initiator
participating in the initiation of the polymerization after
"reverse" ATRP has formed the active catalyst complex. 12
[0161] With this increased level of choice in ligands suitable for
controlled polymerizations, described above, it is now possible to
consider additional aspects of the process. The desire for catalyst
recyclability leads to the understanding that substituents on the
ligand can be also be chosen, or designed, to allow for isolation
of the catalyst complex from the reaction medium by reversibly
changing one or more process parameters such as precipitating the
catalyst. One such suitable parameters can be temperature, as
taught by W. J. Brittian et al., Polymer Preprints, vol. 40 (2), p.
380 (1999) for polyethylene substituted ligands. However, a more
energy efficient process can be developed around chemical
modification of the ligand or catalyst complex to cause
precipitation at the reaction temperature or at lower temperatures.
One specific example of such a mechanism can involve a ligand or
catalyst complex responsive to pH changes or further complexation
with an added solid or salt resulting in the formation of a solid
easily removed from the polymer solution. Another approach would be
the addition of a material that can co-crystallize with the ligand,
in the example described above by Brittian the polyethylene
substituant on the ligand, while having a sufficiently high
molecular weight to precipitate from solution as the temperature is
changed, also has a sufficiently high molecular weight to interfere
with the dynamics of the polymerization due to the bulk of the
substituant in solution. The polymer prepared using this ligand had
a higher molecular weight, lower conversion, and broader MWD than a
material prepared with a normal ATRP catalyst system. A ligand with
a lower molecular weight polyalkane substituant such as BPMODA has
been shown to provide the control expected for ATRP and this
polyalkane group can co-crystallize or interact with a non-attached
added material to allow separation from the reaction medium. Such a
system is suitable for recycle or reuse of the catalyst complex
since the separation from the system can be dependent on a readily
adjustable process parameter. Monomers are added, the catalyst is
made available, the polymerization occurs, the catalyst is
separated by adjustment of one process parameter, filtered and made
available for the next batch as the first parameter is changed back
to allow the catalyst to return to the active state.
[0162] The use of macroinitiators for the preparation of block and
graft copolymers using ATRP as the polymerization process has been
described earlier along with the use of macroinitiators in the
(co)polymerization of macromonomers. It has been determined that
use of an appropriate macroinitiator in a (co)polymerization of a
macromonomer leads to early compatabilization of the polymerization
system and more efficient incorporation of the macromonomer into
the copolymer. This concept will work for other controlled
polymerization systems and also in non-controlled (conventional)
polymerization systems. Indeed, in non-controlled polymerizations
the use of the macroinitiator may even be more critical to allow
both incorporation of the macromonomer into the instantaneously
higher molecular weight copolymer, and to act as a surfactant to
keep the polymerization system in one phase.
[0163] The synthesis of block copolymers in bulk or solution ATRP
can be done either through sequential addition of the required
monomers, or through the isolation of the various macroinitiators
in a more step-wise fashion. The sequential addition of monomers is
by far the less time consuming, practical and easiest method and
potentially lower cost process. Such an approach can assist in the
cross propagation in all controlled polymerization systems when
switching from one monomer to another where a tapered structure at
the end of one block improves the initiation for the next block.
However, this may involve compromising the polydispersities,
homogeneity functionality or interfacial properties of the block
copolymer. A challenging synthetic task has been the synthesis of
block copolymers containing acrylates and methacrylates, since they
are difficult to obtain through other polymerization mechanisms.
Furthermore, even using ATRP it is necessary to ensure full
functionality of the polymer chain ends and to have relatively fast
initiation of the second (or third) block (i.e. fast
cross-propagation). In the case of PBA initiating MMA, it was
necessary to ensure the end group on the PBA was Br, and CuCl was
used as the catalyst, otherwise cross propagation initiation was
slow. Within a sequential addition experiment, this requires that
the PBA be initiated with a bromine containing initiator and CuBr
should be used as the catalyst. On addition of the second monomer
(MMA in this case), CuCl must also be introduced into the reaction
to facilitate halide exchange and thus increase the rate of
cross-propagation relative to the homopropagation of MMA.
[0164] An examination of the molecular weight distributions from
two different experiments, one the synthesis of a diblock copolymer
of PBA-b-PMMA, and the other of a tri-block copolymer
PMMA-b-PBA-b-PMMA is informative. In each case, the PBA was grown
first (with monofunctional and diflinctional initiators
respectively), then the MMA, with CuCl/HMTETA dissolved in it, was
added to the PBA. The molecular weight increased, and there is no
sign of terminated polymer that would correspond to `dead`
macroinitiator. The number average molecular weights,
polydispersities and monomer conversions are given in the examples
section. In each case the conversion first of BA and then of MMA
reached approximately 90%, and the polydispersities remained low
(.about.1.20-1.25). These experiments show that ATRP can be applied
to the synthesis of block copolymers without the need to isolate
macroinitiators, even when there are several factors, such as
cross-propagation rates, that may effect the success of the block
copolymerization.
[0165] These experiments demonstrate that ATRP is a very versatile
method for synthesizing block copolymers, specifically being able
to produce block copolymers with free radically copolymerizable
monomers. This applies to both within water-borne polymerizations
and through sequential monomer additions in bulk
polymerizations.
[0166] The above examples demonstrate an extremely economical way
to make novel block copolymers without isolation and purification
of the intermediate macroinitiator when a second (co)monomer is
added to the polymerization before the first (co)monomers have been
converted to polymer. In "living" radical polymerization systems
three different types of gradient copolymer can be formed in the
second (co)polymerizing block in such continuous block
copolymerizations. When the(co)monomers of the first block are
preferentially incorporated into the (co)polymerizing second block
then an interfacial tapered block can be formed as all the first
(co)monomer is consumed prior to a "pure" second block being
formed. For polymers that undergo phase separation this will
provide a polymer with broader modifiable interfacial boundary. The
length and composition of this tapered block depends of the percent
conversion for the first (co)monomers prior to the addition of the
second (co)monomers. In an elastomeric material this will
significantly modify the properties of the bulk polymer, changing
tensile yield strength, ultimate tensile strength, % elongation and
hysteresis.
[0167] However if the first (co)monomer is more slowly incorporated
into the second block then the second block can be a statistical or
random copolymer of the first and second monomers.
[0168] In the third case, if the first (co)monomer is not readily
incorporated into the polymer then a "reverse" gradient copolymer
would be formed only if the polymerization of the second monomer is
driven to high conversion.
[0169] Thus it is possible to prepare three different types of AB
block copolymers in such continuous block (co)polymerizations
depending on the reactivity ratios of the monomers in the A block
and B block. In a non-limiting discussion of the third case in the
above polemic, consider an A-block with a hydrophylic monomer or a
masked hydrophylic monomer, such as t-butyl acrylate, and then
(co)polymerize the first monomer with a more hydrophobic monomer
that only incorporates the first monomer at low levels, such as
methyl methacrylate. If the second monomer is added while say there
is 20% of the first monomer in solution and the copolymerization
runs to high overall conversion then a gradient copolymer is formed
with a short (co)polymer block comprising a higher concentration of
hydrophylic monomer at the growing polymer tail. This will lead to
surfactant molecules with tunable micellular properties.
[0170] As previously mentioned in this application in emulsion
systems it is often advantageous to add non-complexed redox
conjugate transition metal salt to the aqueous phase to control the
concentration of the complexed redox conjugate in the
polymerization phase. In block copolymers where higher levels of
redox conjugate are required for the preparation of the first block
than the second block and one does not wish longer reaction times
for the preparation of the second block, various methods are
available to control the concentration of each oxidation state of
the catalyst in the reaction. One can either add additional lower
oxidation state transition metal catalyst with the second monomer,
or the concentration of the redox conjugate can be reduced by
adding metal zero, or even a combination of adding both
Cu(I)/Iligand to the organic phase and Cu(II) to the aqueous phase
for a copper based catalyst in an emulsion system.
[0171] In a "reverse" emulsion ATRP, the initial ratio of
CuBr.sub.2/2dNbpy to the standard free radical initiator has a
great effect. The polymerization is much faster when less amount of
the catalyst is employed. This is due to the fact that
CuBr.sub.2/2dNbpy acts as the radical deactivator in the atom
transfer reaction and if all CuBr.sub.2 is reduced to CuBr by
reaction with generated free radicals then the rate is increased.
On the other hand, the molecular weight control of the
polymerization, or more precisely the initiation efficiency, was
little affected by the amount of the deactivator. The comparison of
the molar mass evolution with different ratio of CuBr.sub.2/2dNbpy
vs. the standard free radical initiator is also shown in to be more
or less independent of the initiation efficiency or the amount of
the catalyst which indicates that the CuBr.sub.2 dissolved in water
is not the major cause for the irreversible termination in the
aqueous phase, rather, the termination between first formed free
radicals is mainly responsible for the low initiation efficiency.
With more CuBr.sub.2/2dNbpy, the polydispersity of the obtained
polymer is slightly smaller. This is due to the higher partitioning
of the deactivator in the organic phase, thus afford more efficient
deactivation.
[0172] In emulsions, the particle size is quite sensitive to the
amount of the catalyst. This probably results from the different
ionic strength of the aqueous phase. With more CuBr.sub.2 dissolved
in the aqueous phase, the increased ionic strength weakens the
ability of the surfactant to stabilize the particles. This can
explain why the variation of the particle sizes with the amount of
the catalyst is more pronounced at lower level of the
surfactant.
[0173] Reverse ATRP is the preferred approach in emulsion
polymerization if the target product is a stable small particle
sized latex. In such systems there is a linear increase of
molecular weight with monomer conversion. This indicates that the
number of chains is constant, in other words, chain transfer
reactions are negligible. The products display low polydispersities
(1.2.about.1.5), meaning that nearly all the chains start to grow
simultaneously with the same speed. Both features suggest that the
polymerization can be regarded as controlled. However there is
relatively low initiation efficiency (25-45%, versus 80% for the
homogeneous system). This is calculated based on the theoretical
molecular weight values, assuming that one molecule of standard
free radical initiator generates two radicals. The main reason for
this low efficiency is attributed to the irreversible radical
termination in the aqueous phase, which might include the reaction
between two radicals, or between a radical and CuBr.sub.2 dissolved
in water. The final latex is usually stable, lasting from days to
even more than a year without any sedimentation. The final particle
size is reproducible, in the range of 200 mn. In all the
experiments, it is observed that the measured particle diameter
progressively decreases until 20% to 40% conversion, then keeps
constant after 40% conversion.
[0174] In order to improve the initiation efficiency and control
the level of both redox conjugate states of the transition metal
complex in reverse ATRP, a conventional ATRP initiator (RX) was
added to the "reverse" ATRP emulsion system, with V-50 (a
commercially available free radical initiator) added as the radical
source, in addition to the standard free radical
initiator/CuBr.sub.2 system. Under such conditions, the final
forward ATRP initiator would be a mixture of RX together with
initiator molecules formed from V-50 after reaction of the formed
free radicals with CuBr.sub.2. If RX is dominating, the effect of
termination of the radicals generated by V-50 in the aqueous phase
could be negligible. The concentration of catalyst employed in the
polymerization would also be separated from the amount of standard
free radical initiator added. The advantage of this approach is
that the final particle size may be much smaller than those
obtained from direct ATRP. Under appropriate conditions, the
overall initiation efficiency was improved from 0.2-0.3 for pure
reverse ATRP to .about.0.6 in the presence of ethyl
2-bromoisobutyrate (EBiB), from Aldrich. In addition the level of
catalyst complex and the concentration of different redox conjugate
states can be independently controlled from the amount of added
standard free radical initiator.
[0175] Within the examples provided in this application most
experiments are run on small scale. However, when a larger scale
"reverse" ATRP emulsion polymerization was carried out in a 250 ml
reactor with mechanic stirring (.about.400 rpm), the results were
identical to the small scale experiment. The experimental
conditions were identical and within experimental error, the
experiments have similar kinetics, molecular weight evolution and
particle size indicating further scale up should be controlled and
predictable.
[0176] The use of conventional xadical initiators in ATRP in the
presence of complexes of transition metals in their higher
oxidation state, has been disclosed in prior applications and
referred to as "reverse" or "alternative" ATRP. The range of
"standard free radical initiators" that can be used in such
"reverse" ATRP reactions can now be expanded to include peroxides.
This expansion is demonstrated by the results of the homogeneous
"reverse" copper-mediated ATRP using as the initiator benzoyl
peroxide (BPO) which are presented, and compared with those using
azobisisobutyronitrile (AIBN).
[0177] Homogeneous "reverse" ATRP can now be successfuilly carried
out, or initiated by, decomposition of either diazo-compounds or
peroxides. For AIBN initiated polymerization, addition of CuBr has
little effect while "reverse" ATRP occurs efficiently in the
presence of CuBr.sub.2 which can scavenge initiating/growing
radicals and form CuBr and RBr species. In contrast, CuBr.sub.2 is
an inefficient component of "reverse" ATRP initiated by BPO due to
fast electron transfer from the resulting Cu(I) to BPO and
coordination of benzoate anions to copper. However, the
polymerization initiated by BPO can be controlled in the presence
of a sufficient amount of CuBr. After the induced decomposition of
BPO, growing radicals are deactivated by Cu(II) species to produce
bromine terminated oligomers and Cu(I) species. Both Cu(O.sub.2CPh)
and CuBr can then successfully catalyze ATRP.
[0178] Charged ligand-metal complexes 1 and 2 were synthesized and
tested as their Cu(II) complexes in the reverse ATRP of styrene, MA
and MMA. The influence of the charged coordination site should be
seen in two effects:
[0179] 1. the stabilization of the Cu(II) species and therefore the
formation of a highly active catalyst for ATRP.
[0180] 2. due to the ionic nature of the bond between copper and
the charged coordination side of the ligand a more stable complex
should result. 13
[0181] Cu-Complexes of Charged Ligands
[0182] Different polymerization reactions using Complex 1 as
catalyst were run and in bulk polymerization lead to higher
molecular weight products when compared with non-charged polyamines
as ligands. However the catalyst also showed decreased
activity.
[0183] The motivation to use the tripodal charged ligand, Complex
2, was twofold. First, because Me.sub.6TREN, which has a similar
structure, forms highly active complexes for ATRP, it was
determined that a charged ligand with the same geometry of its
related Cu-complex should also show an enhanced activity. As a
second aspect, it was desired to evaluate the influence of the
charged coordination site by comparing the activities of complex 2
with Me.sub.6TREN-CuBr. The complex 2 showed a good activity in the
polymerization of styrene and MMA but polymerized MA more
slowly.
[0184] Earlier in this application the preparation of novel graft
copolymers wherein the graft (co)polymer was attached to the
backbone (co)polymer within the grafted (co)polymer chain was
described. Previous applications disclosed several other approaches
to prepare normal topology graft copolymers through utilization of
controlled polymerization processes including copolymerization of
the primary monomer with a known (often low) concentration of
another monomer which contains a second functional group capable of
initiating ATRP directly, or a copolymer comprising a
monomer-containing a second-functional group comprising a masked
ATRP initiator, or functionalization techniques on a preformed
backbone to form initiation sites, all of which can be employed as
functional macroinitiators for the growth of pendant graft
(co)polymer chains from the backbone. The latter process, of
(co)polymer functionalization, has already been confirmed for the
controlled polymerization of vinyl monomers from poly(vinyl
chloride) and poly(dimethylsiloxane) macroinitiators. The graft
copolymerization from chlorosulfonated polyethylene has also been
disclosed in earlier applications. This present application
describes the modification of, and subsequent polymerization from,
a commercially available poly(ethylene-co-glycidyl methacrylate)
copolymer. Examples describing the ring-opening of the epoxide
groups with chloroacetic acid are given along with subsequent graft
(co)polymerization with styrene, benzyl acrylate and methyl
methacrylate as exemplary vinyl monomers. Hydrolysis of the benzyl
groups in the benzyl acrylate graft copolymer are also taught which
leads to the synthesis of amphiphillic graft copolymers with a
polyethylene backbone.
[0185] The use of an organic polymer-supported ligand has been
disclosed in an earlier application. The specific improvement now
disclosed is based on the use of a linear tetramine immobilized on
crosslinked polystyrene as the ligand, forming the transition metal
complex and critical application of the recognition of the
importance of the redox conjugate in obtaining a fully controlled
system. Based on the polymeric nature of the support, the systems
should exhibit high compatibility between the support and the
growing chains. Supports with a high loading of ligands on the
surface (1.5 mmol/g) were formed. Several polymerizations with
various monomers were carried out and the results are reported in
the examples section. The polymer supported tris(2-aminoethyl)amine
(s-TREN) showed the best results for methyl acrylate (MA)
polymerizations. In the case of styrene (St) and methyl
methacrylate (MMA), the polydispersities were high, and the
polymerizations were slower compared to methyl acrylate.
[0186] In order to obtain better control over the reaction
N,N-Bis(2-pyridylmethyl)-2-hydroxyethylamine (HO-BPMEA) was
immobilized on a commercially available Merrifield resin containing
benzyl chloride functional group, which is used widely for peptide
synthesis and combinatorial synthesis of small organic molecules.
Methyl acrylate (MA) was chosen for study since HO-BPMEA provided
one of the best-controlled solution polymerizations of MA. In the
first experiment, a bimodal molecular weight distribution was
observed by SEC. The reason for the bimodal molecular weight
distribution was not immediately clear, but it was surmised that
the initial growing radicals cannot easily access the deactivator
and thus continue to polymerize in uncontrolled manner with normal
free radical termination reactions occurring. This gives rise to
the polymer seen in the high molecular weight peak. After
generation of enough amounts of deactivator by termination
reactions a fully controlled ATRP polymerization then proceeds
forming the material seen in the low molecular weight peak.
[0187] In order to obtain control of the ATRP process from the
instant of initiation of the polymerization process, it is
preferred that one enhance the deactivation process. Deactivator,
Cu(II)Br.sub.2 together with activator Cu(I)Br, was added at the
beginning of the reaction, and therefore both copper species should
be complexed by the solid-supported ligand in proximity to each
other. In a series of examples in which the total amount of copper
species was kept the same, the effect of differing ratios of redox
conjugates were determined. Results from use of three different
ratios of Cu(II)Br.sub.2 to Cu(I)Br are reported. With higher
percentage of Cu(II)Br.sub.2 in the initial catalyst complex, the
molecular weights were closer to the expected values with lower
polydispersity (See Entry 2-5 in Table 26). These observations
suggest that the higher available concentrations of Cu(II)Br.sub.2
lead to an increase in the rate of deactivation, thus improving
control.
[0188] In a stirred reaction vessel, both the mobility of the
particles carrying the immobilized catalyst and the diffusion of
the polymer coils in the reaction mixture can affect the level of
control in an ATRP polymerization process. If the catalyst is
closely attached to a bulky support this hinders the diffusion of
the growing chain end to the catalytic site. In homogeneous ATRP,
the rate constant of activation in ATRP is typically in the range
of k.sub.act.apprxeq.10.sup.0 L mol.sup.-1 s.sup.-1 and that of
deactivation k.sub.deact.apprxeq.10.sup.7 L mol.sup.-1 s.sup.1.
Diffusion of the active and dormant chain ends to the activator and
deactivator immobilized on the surface may be in the range of
microseconds or milliseconds. Therefore, the overall rate of
activation should not be affected significantly
(k.sub.1>>k.sub.act- ). However, with a ligand supported
catalyst complex the overall rate of deactivation may be
significantly slower than with a homogeneous catalyst and diffusion
may become rate-determining (k.sub.2<<k.sub.deact). This
would result in poor control due to slow deactivation and requires
a higher concentration of the deactivator than under homogeneous
conditions. This can explain why an apparent large excess of the
deactivator, the redox conjugate in ATRP, or "persistent radical"
in other controlled radical polymerization processes, is needed to
gain control in heterogeneous systems; and also why polymerization
occurs in spite of the enormous excess of Cu(II), when compared to
homogeneous systems. Deactivation rate is enhanced by the addition
of deactivator at the beginning of the polymerization. Increasing
the initial concentration of deactivator enhances the probability
that growing radicals will react with it and be transformed to the
dormant species. Also, an increase in the number of particles
increased the number of catalyst sites in the mixture, and caused a
higher probability of deactivation in the polymerization.
[0189] This understanding of the critical role of the "deactivator"
or "persistent free radical" is operable in most controlled radical
polymerization systems and will lead to narrower molecular weight
distributions, or more precisely tailored broader molecular weight
distributions if so desired, and higher functionality, due to
control being imposed on the system at the first instance of
initiation of polymerization.
[0190] Such continued increase in the understanding or the role of
the components of the catalyst complex, particularly the role of
the redox conjugate in ATRP or "persistent radical" in other
controlled radical polymerizations, have allowed further advances
to be made on the range of initiators that can be employed for
controlled radical polymerization. One of the most potentially
useful applications is the use of modified surfaces for the direct
initiation of controlled polymerization. Unlike prior art processes
described by Ejaz, M.; Yamamoto, S.; Ohno, K.; Tsuji, Y.; Fukuda,
T., Macromolecules, vol. 31, p. 5934 (1998); Husseman, M.;
Malmstrom, E. E.; McNamara, M.; Mate, M.; Mecerreyes, D.; Benoit,
D. G.; Hedrick, J. L.; Mansky, P.; Huang, E.; Russell, T. P.;
Hawker, C. J., Macromolecules, vol. 32, p. 1424 (1999), which do
not prepare 100% tethered polymer we have now developed and defined
conditions for controlled polymerization from surfaces that can
accomplish this task without the use of any sacrificial initiator,
i.e. without the production of any non-tethered polymer. In this
way all (co)polymer produced in the polymerization process is
"controlled" and is attached to the surface at the desired site,
and leads to a brush, or carpet pile, growth of active chains from
each known activated initiator site. Each polymer chain remains
active and can continue to (co)polymerize radically active monomers
forming block copolymers and functional chain end materials, or in
this case functional or tailored surfaces.
[0191] The practical advantage, or economic incentive for such a
system, exemplified by a discussion of ATRP but as indicated
earlier applicable to all controlled polymerization systems
operating through or in conjunction with a "persistent radical"
effect, is that the solution of the transition metal complex in
monomers, and optional solvent, can be used many times over in
continuous processes for polymerization from surfaces with attached
or tethered initiators by sequential immersion of new materials in
the medium. The molecular weight of the attached polymer being
dependent on time of immersion in the solution. In addition block
copolymers are prepared by moving the surface from the first
polymerization bath to a second solution containing transition
metal complexes and monomers most appropriate for the second block
copolymerization. Since the polymer retains an active initiation
group at the `dormant` chain end intermediate process steps can be
carried out between sequential polymerizations. An example is
forming a mask and depositing fresh initiator on the conductive
masked material to allow polymerization from both the original
polymer and new initiator site to produce a uniform insulating
layer. This process can be reproduced easily by repeating the
steps. There is no waste polymer produced and the monomer/catalyst
solutions can be continuously employed by addition of monomer.
[0192] This advance was also attained by consideration and
application of the fundamental dynamics of controlled
polymerization reactions. For controlled growth from a surface one
requirement is that the "persistent radical," or deactivator, be
present in the liquid phase. Rather than build up the required
concentration of deactivator by conducting a normal polymerization
in the contacting solution in addition to polymerization from the
surface tethered initiator, one can add of an excess of the redox
conjugate of the transition metal complex in ATRP, or an excess of
the stable free radical in thermally labile stable free radical
mediated polymerization, to control the polymerization from the
first moment of initiation of polymerization from the tethered
initiator.
[0193] The extension of ATRP to polymerize styrene and acrylates
from surfaces was accomplished through the use of 2-bromoisobutyryl
groups bound to surface functional silicon wafers as initiator,
enabling the synthesis of surface bound polymer brushes. From this
approach, homopolymers of styrene and methyl acrylate, as well as
block copolymers from styrene and acrylates were grown from a
surface. By self-assembly of a 2-bromoisobutyryl functional
trichlorosilane on silicon wafers, monolayers of ATRP initiating
groups were deposited. Polymerization was then conducted, in the
presence of a homogeneous catalyst system of
Cu(I)Br/4,4'-di-n-nonyl-2,2'-bipyridine (dNbpy), as well as
Cu(II)Br.sub.2/dNbpy deactivator (3-5-mole % relative to Cu(I)Br).
Addition of Cu(II)Br.sub.2 at the beginning of the polymerization
suppressed termination reactions, allowing for higher retention of
alkyl halide end-groups. Thus, the addition of deactivator, or
"persistent free radical" at the beginning reaction surprisingly
avoids and significantly improves upon the need to add free,
untethered initiator, as previously reported by other workers for
controlled polymerization from surfaces.
[0194] The growth of polymer chains from the surface of silicon
wafers, without attendant polymerization in the contacting
solution, was confirmed by ellipsometry measurements of film
thickness. Thus, in the homopolymerization of styrene and methyl
acrylate, a linear increase in film thickness with time was
observed, indicative of successful ATRP from the wafer. Due to the
extremely low loading of the polymer onto the silicon substrate,
direct analysis of surface grafted polymers could not be performed.
However, chain extension reactions from surface bound polymers were
done, verifying the presence of ATRP active alkyl halide
end-groups. From this approach, surface-tethered block copolymers
from styrene and various acrylate monomers were synthesized,
indicating that deactivation by Cu(II) had occurred. This method
also enables the tuning of surface properties by polymerizing
acrylate monomers of varying composition. In particular,
hydrophobic and hydrophilic surfaces were prepared by chain
extending wafer-bound p(Sty) with
3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl acrylate
or t-butylacrylate, respectively. Hydrophilic surfaces were then
obtained by acidic hydrolysis of the tethered p(Sty-b-tBA) to yield
the amphiphillic block copolymer.
[0195] Understanding the kinetics of initiation and deactivation is
also important in the preparation of low molecular weight polymers,
particularly low molecular weight block copolymers suitable for use
as surfactants or reactants, where molecular weight control and
high functionality is required both for efficient crossover from
the A (co)monomer(s) to the B (co)monomers and for the application,
the presence of the correct level of deactivator prior to
initiation is required. This is exemplified by the preparation of
hermaphrophylic oligomeric block copolymers for surfactant
applications. In the preparation of polystyrene/t-butylacrylate
block copolymers with polystyrene blocks exhibiting a MW.sub.n of
1050 not only is it advantageous to add 5% of CuBr.sub.2 but also a
polar solvent such as acetone at levels that will ensure solubility
of the deactivator. Under such conditions the initial polystyrene
block was formed with narrow MW distribution and cleanly moved to
higher molecular weight when the second monomer was added.
[0196] The importance of functional control attainable through ATRP
is further demonstrated through the capacity to prepare block
copolymers from disparate types of monomers by sequential
modification of end groups, expediently preparing a macroinitiator,
with the appropriate end group for further chain extension. Two
approaches to a new type of organic/inorganic polymer hybrid,
well-defined organic polymer-polyphosphazene block copolymers are
feasible. One method initially described in U.S. patent application
Ser. No. 09/018,554 is the preparation of a polyphosphazine
macroinitiator for an ATRP polymerization. Another approach herein
disclosed is to prepare an organic macroinitiator by ATRP and
conversion of the radically transferable atom into an initiator
site for the polymerization of the phosphorimine. This is
accomplished by converting the end group first into an azide and
then reacting the tele-azidopolymer with
2,2,2-tris(trifluoroethyl)phosphite to convert the functional end
group into a new initiator molecule, a macroinitiator with a
phosphoranimine end group. Such a macroinitiator can be used for
the preparation of block copolymers by initiating the
polymerization of monomers such as
P-tris(2,2,2-trifluoroethoxy)-N-trimethylsilyl phosphoranimine.
[0197] A vast number of methodologies have been reported for the
preparation of organic/inorganic hybrid materials. Traditional
approaches include the use of sol-gel chemistry to synthesize
ceramic materials with polymeric components either covalently bound
or interpenetrated with the inorganic phase. Alternatively,
inorganic/organometallic monomers and polymer systems can be
combined with their organic counterparts to prepare hybrid polymers
with inorganic blocks, or pendant groups. Through the utilization
of inorganic (macro)initiators or monomers, atom transfer radical
polymerization (ATRP) has been demonstrated to be a versatile
method for the preparation of hybrid materials. ATRP has been
successfully used to synthesize a variety of well-defined
(co)polymers from an exemplary range of acrylates, methacrylates
and styrenes. Due to the radical nature of ATRP, a wide range of
monomers and polymers can be employed, provided that interaction
with both active species of the catalyst is avoided. Inorganic
(macro)initiators for ATRP only require the incorporation of an
activated alkyl halide group (e.g., .alpha.-haloesters, benzyl
halides) into the targeted inorganic polymer, or substrate.
[0198] Through this approach, poly(dimethylsiloxane) (PDMS) and
silicon wafers, functionalized with initiator groups, have been
used as macroinitiators for ATRP for the preparation of hybrid
materials. Similarly, inorganic monomers have been (co)polymerized
by ATRP from organic (macro)initiators. Specifically, polyhedral
oligomeric silsesquioxane (POSS) monomers have been utilized for
the synthesis of hybrid polymers.
[0199] The synthesis of block and graft copolymers of PDMS and
poly(styrene, acrylates and methacrylates) was conducted using
ATRP, as outlined earlier, through the use of alkyl halide
functional PDMS as a macroinitiator in the ATRP of vinyl monomers.
The incorporation of ATRP initiating groups into PDMS was achieved
through hydrosilation of silane-terminated PDMS with either
4-vinylbenzyl chloride, or 3-butenyl 2-bromoisobutyrate.
Previously, only p(-DMS-b-Sty) di-, triblock and p(DMS-g-Sty) graft
copolymers could be prepared due to the limited efficiency of
benzyl chloride groups to initiate ATRP of acrylates and
methacrylates. Now PDMS has been successfully functionalized with
2-bromoisobutyryl groups, allowing for the synthesis of AB block
copolymers of PDMS and poly(acrylates) or poly(methacrylates).
Additionally, the synthesis of p(Sty-b-DMS-b-nBA) and
p(Sty-b-DMS-b-MMA) triblock copolymers has also been performed. The
synthetic route for triblock copolymers of styrene,
hexamethylcyclotrisiloxane and (meth)acrylate monomers is
accomplished through a cross mechanism block copolymerization
starting with the living anionic polymerization of styrene to
produce a polystyrene chain (Mn=4,600; Mw/Mn=1.09) which was used
to initiate the ring-opening polymerization of
hexamethylcyclotrisiloxane (D3). Subsequent quenching of the
lithium silanoate chain end of the p(Sty-b-DMS) block copolymer
with chlorodimethylsilane yielded a silane terminated chain end
(Mn=7,760; Mw/Mn=1.15). A macroinitiator for ATRP was then prepared
by hydrosilation of the silane-functional p(Sty-b-DMS) copolymer
with 3-butenyl 2-bromoisobutyrate. ATRP with the p(Sty-b-DMS)
macroinitiator with either n-butyl acrylate (nBA) or methyl
methacrylate (MMA) enabled the synthesis of ABC triblock
copolymers. The synthesis of these triblock copolymers was
confirmed by SEC analysis. The SEC chromatogram showed that the
synthesis of well-defined polymers at each step of the block
copolymerization, going from p(Sty) to p(Sty-b-DMS) anionically,
followed by addition of n-butyl acrylate (Mn=10,200; Mw/Mn=1.18),
or methyl methacrylate (Mn=10,100; Mw/Mn=1.21) using ATRP.
[0200] One approach towards the synthesis of organic/inorganic
hybrids disclosed above and in earlier applications has been the
incorporation of both well-defined inorganic and organic components
into a material. Previously, inorganic initiators comprising
benzyl-chloride functionalized cyclic siloxanes and polyhedral
oligomeric silsesquiokanes (POSS) were applied to the ATRP of
styrene. This work has now been extended to include the use of
monofunctional methacryloyl/styryl POSS monomers (Scheme 10).
14
[0201] Polysiloxane monomers comprised of methacryloyl and styryl
groups with bulky, POSS moieties, were applied to ATRP systems.
Previous work in the literature reported the conventional radical
polymerization of Sty-POSS and MMA-POSS. The introduction of a POSS
cube into a polymer chain has been demonstrated to effect chain
mobility, thermal behavior and the overall mechanical strength of
the hybrid material. However, the synthesis of POSS-based
(co)polymers has not yet been reported using controlled radical
processes. POSS-polymers prepared using controlled radical
polymerization methods offer the advantage of possessing end-group
functionalities capable of reinitiating polymerization. This allows
for the synthesis of block copolymers of POSS, such as
thermoplastic elastomers, with a soft middle segment and
POSS-polymers at the periphery. Additionally, more complicated
topologies can be achieved through controlled radical
polymerizations, allowing for the synthesis of star polymers and
star block copolymers. Thus, the application of POSS-based-monomers
to ATRP can yield a wide range of hybrid materials possessing both
well-defined inorganic and organic polymer segments.
[0202] POSS polymers represent a novel class of hybrids that has
been demonstrated to impart greater thermal stability and
mechanical strength to a material. Structurally, POSS is a cubic
siloxane octamer, possessing an outer diameter of 1.5 nm. POSS
groups can be incorporated into polymer chains by polymerization of
a monofluctional POSS monomer, bearing some polymerizable group. It
is the inclusion of these bulky, inorganic pendant groups that
gives POSS polymers their unusual structure and properties. While
POSS polymers and materials have been prepared from a variety of
methods, the application of POSS monomers to ATRP allows for
greater control of polymer molecular weight, topology and
composition. By using ATRP, well-defined homo-, block and random
copolymers can be synthesized. Homopolymers of a
methacryloyl-functional POSS monomer (MA-POSS) have been
synthesized by solution ATRP in toluene. Random copolymers can also
be prepared by copolymerization of either styryl-functional POSS
(Sty-POSS) or MA-POSS with conventional vinyl monomers (e.g.,
styrenics, (meth)acrylics). Additionally, by the use of
poly(acrylate) macroinitiators, both AB and ABA block copolymers
has been prepared, with soft middle segments from the
macroinitiator, and hard POSS segments obtained from chain
extension reactions. In particular, the synthesis of a
p(MA-POSS)-b-p(nBA)-b-p(MA-POSS) triblock copolymer has been
conducted. As determined from SEC, efficient chain extension of
MA-POSS from the p(nBA) macroinitiator was observed.
[0203] These experiments discussed above and reported later
demonstrate that the preparation of hybrid materials from POSS
monomers, using ATRP, has been conducted. The synthesis of
well-defined homopolymers, random and block copolymers from
controlled radical polymerization resulting in the preparation of
controlled hybrid (co)polymers containing functional inorganic
groups. The synthesis of POSS-PMMA homopolymers and copolymers
incorporating either POSS-Sty or POSS-MMA monomers has
been-successfully demonstrated, using ATRP. The types of POSS-based
polymers that have been prepared by ATRP are presented in scheme
11. 15
[0204] The synthesis of hybrid organic/inorganic silicate
nanoparticles is hereby demonstrated via polymerization of vinyl
monomers from initiator-functionalized particles. The first
approach was use of a benzyl chloride functional silicate particles
as initiator, T. E. Patten, Polymer Preprints, vol. 40(2), p. 354.
Difficulties in optimizing the conditions for the ATRP of styrene
from the benzyl chloride initiator particles were encountered,
presumable due to inefficient initiation from the benzyl chloride
groups. To overcome this difficulty, the synthesis of nanoparticles
possessing 2-bromoisobutyryl functional group was pursued.
[0205] The synthesis of 2-bromoisobutyryl functional silicate
particles was attempted using both a modified Stober process
(Philipse et al., Journal of Colloid and Interface Science, vol.
128, p. 121 (1989)) and a surfactant template approach (Schmidt et
al, Adv. Mater., vol. 9, p. 995 (1997)). Using the Stober process,
silica particles with methacrylate and 2-bromoisobutyryl surfaces
were prepared.
[0206] A surfactant template approach was also conducted in the
synthesis of functional particles. Using the surfactant system,
conditions were ascertained for the synthesis of soluble silicate
particles bearing trimethylsilyl methacrylate and 2-bromoisobutyryl
as surface modifying initiator groups. Elemental analysis of the
particles indicated that bromine was successfully incorporated to
the particles.
[0207] Procedures for functional silica particles from a modified
Stober process have been reported (Philipse et al., Journal of
Colloid and Interface Science, vol. 128, p. 121 (1989). In this
process, monodisperse particles are prepared from hydrolysis and
condensation of tetraorthosilicate (TEOS) and surface silanol
groups of the particle co-condensed with a functional
trialkoxysilane. For the preparation of a particle suitable as an
initiator for ATRP the functional trialkoxysilane bears a
functional group containing a radically transferable atom, in the
first case, 3-(methacryloxy)propyl-trimethoxysilane (MPS). In
another approach to the preparation of functional particles, this
approach was repeated, using
3-(methacryloxy)propyl-trimethoxysilane as the surface treating
agent. This was also extended to 3-(2-bromoisobutyryloxy)propylt-
rimethoxysilane (BIB-TMS). The general scheme for the synthetic
reactions using the Stober process are presented in FIG. 8.
[0208] The synthesis of monodisperse, soluble, functional particles
was also conducted in the presence of a surfactant. In such
systems, surfactants form micelles, which serve as nanosize
templates and reactors for the preparation of particles. The
surfactant then stabilizes the surface of the particle, allowing
for consecutive condensation reaction of the particle with other
silanes. In this way, various functionalities can be introduced to
the surface of the particle. A key feature of this system is that
soluble particles can be prepared by deactivation of surface
silanol groups with monoalkoxysilane and disilazanes.
Monochlorosilanes can also be used to both deactivate surface
silanol groups and introduce functionality to the particle. The
general synthetic scheme for the synthesis of particles from this
approach is presented in FIG. 9.
[0209] Functional particles were prepared from a variety of methods
using this approach. In all cases, methyltrimethoxysilane should be
used as the core forming component, but functional trialkoxysilanes
can be co-condensed with methyltrimethoxysilane, followed by
surface deactivation, to prepare functional particles.
Additionally, particles can be prepared comprising solely of a
methyltrimethoxysilane, followed by surface deactivation with
functional mono-alkoxy/chlorosilanes and disilaaanes. Soluble
spherical particles suitable as ATRP initiators were formed.
[0210] The synthesis of methacryloyl functional particles was
conducted by co-condensation of
3-(methacryloxy)propyltrimethoxysilane (MPS) and
methyltrimethoxysilane in 50%-wt mixture of the silanes followed by
surface deactivation with methoxytrimethylsilane and
hexamethyldisilazane.
[0211] Functional single walled carbon nanotubes, i.e., elongated
fullerenes, are also promising materials for the preparation of
similar hybrid materials, in this case rigid rod, carbon based,
reinforced nanocomposites. Currently, there are two technical
problems associated with the development of carbon nanotubes as
reinforcing fibers, for composite materials. The first is that the
nanotubes tend to aggregate and form bundles; whereas ideally the
fibers should be dispersed within the polymer matrix. The second
problem is that the nanotubes should be sufficiently well bonded to
the polymer matrix so as to transfer any mechanical load to the
fiber from the polymer, as opposed to the two slipping past each
other. Normally, carbon nanotubes are insoluble suspensions of
aggregated nanotubes. It has however been reported that nanotubes
can be dispersed in organic media by functionalization at the ends
of the tubes with carboxylic acid end groups subsequently
esterified with long alkyl chain alcohols. (J. Chen et. al.;
Science, vol. 282, p. 5 (1998).) Such materials however would not
exhibit interaction/adhesion to the matrix.
[0212] By using a similar methodology to that disclosed above for
monodisperse silica particles, tubes functionalized with carboxylic
acid groups can be converted into groups suitable to initiate the
polymerization of vinyl monomers by known controlled polymerization
processes. For initiation of ATRP they may just be alkyl halides,
which would provide for the formation of a majority of polymeric
groups at each tube end; additionally, the polymer segments would
be of controlled (pre-defined) molecular weight and of low
molecular weight distribution. The (co)polymer can be selected to
dissolve in the matrix material providing good adhesion or indeed
be the desired matrix material and a true nanocomposite. Such
well-defined polymer segments would also contain the starting
functional group at each chain end which could be further modified
using organic chemistry techniques to yield other functional
groups, i.e., amines, carboxylic acids, alcohols, allyl,
phosphonium, thiol, azide, etc.
[0213] In the description of the preparation of hybrid materials
the polymerization of a single monomer has been described, but more
complex structures can be formed as well. For example, the polymer
composition can be adjusted to prepare block copolymers (to induce
a variety of morphologies), or gradient/statistical copolymers
(mixtures of two or more monomers polymerized simultaneously). Such
materials would be expected to display novel morphologies and
consequently, unique physical and structural properties based on
control over the nanophase separation and resulting large scale
order.
[0214] The reinforced materials would be unique in that the
reinforcing agent, the organic/inorganic composite or the
nanotubes, would reinforce the material on the molecular scale.
Such benefits would allow for easier processing of an essentially
homogeneous thermoplastic composite material by extrusion or
injection molding, or the end group functionality could be employed
in cross-linking reactions in a reaction injection molding type
process to form a nano-thermoset composite. Both of these types of
composites would be useful in the development of high strength
fibers films and parts.
[0215] Although a variety of monomers have been successfully
polymerized in a well-controlled manner through implementation of
the teachings of the inventors and others, the "living"/controlled
radical polymerization of vinyl acetate has not yet been
successful. The importance of controlling vinyl acetate
polymerization arises not only from its industrial importance, but
also from the fact that vinyl acetate has so far been polymerized
only via a radical mechanism.
[0216] We can now report that a robust process for incorporation of
vinyl acetate into controlled polymerization has been
developed.
[0217] Polymerization of vinyl acetate was carried out using
CCl.sub.4 as the initiator in the presence of an
Fe(OAC).sub.2/PMDETA
(PMDETA=N,N,N',N",N"-pentamethyldiethylenetriamine) complex.
Polyvinyl acetate with a wide range of molecular weights were
synthesized in a predictable fashion in high yields by varying the
ratio of the initial concentrations of monomer to initiator. The
resulting polyvinyl acetate was used as an efficient macroinitiator
for the synthesis of block copolymers using typical ATRP catalytic
systems.
[0218] However, more detailed kinetic studies revealed that the
first stage polymerization was not obeying atom transfer radical
polymerization behavior but was an improved redox-initiated radical
telomerization with CClA acting as both the initiator and the chain
transfer reagent. Use of this polymer as a macroinitiator for block
copolymerization was due to the chain extension with the radically
transferable atom being provided by the tail trichloromethyl end
groups rather than head --CH(OAc)--Cl groups. This is a therefor a
novel combination of a novel iron mediated redox telomerization of
vinyl acetate and a controlled polymerization of radically
(co)polymerizable monomers utilizing one catalyst rather than
extension of ATRP to vinyl acetate. The materials prepared by this
sequential combination of two controlled polymerization processes
are novel and useful.
[0219] The redox-initiated radical telomerization was studied.
Typically, CCl.sub.4 or RCCl.sub.3 is used as the telogen and salts
of transition-metals, such as iron or copper, are used as the
catalysts. Results suggested that polymerization of VOAc with
CCl.sub.4 as the initiator in the presence of the
Fe(OAc).sub.2/PMDETA complex was a redox-initiated radical
telomerization (Scheme 12). 16
[0220] Thus, the telomerization was initiated by halogen
abstraction from CCl.sub.4 by Fe(OAc).sub.2/PMDETA. However,
different from typical ATRP where the chain transfer constant to
the transition-metal salt (e.g., CuCl.sub.2, FeCl.sub.3) is much
greater than that to the telogen/initiator, the major chain
transfer pathway in the CCl.sub.4/Fe(OAc).sub.2/PMDETA system was
likely transfer to initiator. In other words, CCl.sub.4 acted as
both the initiator and the main transfer reagent an INIFER (Scheme
12, Steps 1 & 4). Since the chain transfer constant to
CCl.sub.4 in the polymerization of vinyl acetate is about 1 under
the reaction conditions, the ratio of consumed monomer to CCl.sub.4
remained approximately constant throughout the polymerization. As a
result, polymers with fairly constant molecular weights were
obtained.
[0221] The preparation of similar block copolymers have been
reported previously, also using ATRP in conjunction with
trichloromethyl terminated polyvinyl acetate. In that preparation,
the macroinitiator was synthesized using CHCl.sub.3 as a transfer
agent in polymerization of vinyl acetate initiated by AIBN. Since
the transfer coefficient for CHCl.sub.3 is very low (C.sub.tr=0.01)
and it is more difficult to prepare polymers in high yield with
good functionality and without contamination with the end groups
originating from the AIBN initiator and molecular weight control is
poor. By contrast the novel application of CCl.sub.4 as an
initiator and transfer agent for the preparation of a polyvinyl
acetate macroinitiator gives better control of end groups and a
transfer coefficient closer to C.sub.tr=1, provides polymers with
lower polydispersity and predictable molecular weights even in the
presence of small amounts of the transfer agent.
[0222] The same catalyst system can be used for both block
copolymerization steps even though two different polymerization
mechanisms are operating simplifying the process and reducing the
cost for preparation of these useful materials.
[0223] In summary, the polymerization of vinyl acetate using
CCl.sub.4 as the initiator in the presence of Fe(OAc).sub.2/PMDETA
provided polymers with degrees of polymerization predetermined by
the ratio of the reacted monomer to the introduced initiator. The
high level of functionality in the polyvinyl acetate has been
successfully used for subsequent block copolymer formation by
ATRP.
[0224] This system should also be applicable to other monomers that
are currently difficult to polymerize under fully controlled
conditions, including vinylidene fluoride which would lead to a
PVDF/ATRP (co)polymer block copolymer.
[0225] If one wishes to prepare ABA block copolymers with a vinyl
acetate mid block then one can use a difunctional INIFER such as an
.alpha.,.omega.-dichlorobromo-alkane.
[0226] This sequence of synthetic steps can also be reversed, where
a well-defined macroinitiator is synthesized by ATRP and then used
for polymerization of a second block by redox type polymerization.
This combination can exploit the advantages of both methods, i.e.,
the wider range of (co)polymerizable monomers and the
well-controlled processes. This approach to prepare block
copolymers containing vinyl acetate is demonstrated by the use of a
bromo-terminated poly(n-butyl acrylate) as a macro initiator in the
redox initiation of vinyl acetate. The ATRP produced macroinitiator
initiated the polymerization of vinyl acetate in the presence of
CuBr/1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradeca- ne
(Me.sub.4-Cyclam) in 50 vol.-% ethanol.
[0227] It has been determined that for polymerization of n-butyl
acrylate using CuBr/Me.sub.4-Cyclam with methyl 2-bromopropionate
was a relatively poor initiating system for controlled
polymerization. Presumably, the metal complex can abstract the
halogen atom from the initiator to form a radical but the
deactivation rate (abstraction of the halogen from metal by the
growing radical) is much slower than for other catalyst systems.
Slow deactivation results in poor control and resembles a
redox-type initiation. Based on this observation, it was expected
that this catalyst could activate the bromo-terminated poly(n-butyl
acrylate) chain to form macroradicals which would then initiate the
polymerization of vinyl acetate.
[0228] This ligand/catalyst system also allowed successful
incorporation of (meth)acrylamides including
N,N-dimethylacrylamide, N-t-butylacrylamide, and
N-(2-hydroxypropyl)methacrylamide into controlled polymerization
systems, allowing the preparation of homopolymers with functional
termini capable of acting as macroinitiators for the preparation of
block copolymers. These (meth)acrylamide monomers required a slowly
deactivating system to build up significant molecular weight at
each activation cycle. The optimum approach for the preparation of
block copolymers is the preparation of the non-acrylarnide block,
by atom transfer polymerization of free radically (co)polymerizable
monomers and use of this macroinitiator for a second atom transfer
initiated polymerization of N,N-dimethylacrylarnide,
N-t-butylacrylamide, and N-(2-hydroxypropyl)methacrylamide in a
similar manner to vinyl acetate employing the same
CuBr/1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetrad- ecane
(Me.sub.4-Cyclam) catalyst complex moderated by presence of the
redox conjugate.
[0229] In this manner (meth)acrylates-b-(meth)acrylamide block
copolymers were prepared.
[0230] A poly(n-butyl acrylate) macroinitiator was prepared using
methyl 2-bromopropionate and CuBr/PMDETA in the presence of 20
mol-% of Cu(II)Br.sub.2 with respect to CuBr. This combination of
initiator and catalyst/catalyst redox conjugate afforded
well-defined polybutyl acrylate with a terminal bromine end group
as determined by ESI MS analysis. A chain extension experiment with
methyl acrylate supported the high degree of end group
functionality. These two results indicate the presence of the
bromo-end groups in polybutyl acrylate. The polybutyl acrylate
macroinitiator was copolymerized with vinyl acetate using
CuBr/Me.sub.4-Cyclam in the presence of 20 mol-% of Cu(II)Br.sub.2
relative to CuBr in 50 vol.-% ethanol at room temperature.
[0231] A polymerization without addition of Cu(II)Br.sub.2 yielded
a product with a higher molecular weight shoulder. The added
Cu(II)Br.sub.2 can deactivate the growing pVAc chain and thus
prevent transfer or termination by coupling. However, the rate of
deactivation is still much lower than the propagating rate, leading
to the polymer with relatively high polydispersity. The .sup.1H NMR
spectrum showed that the product contains poly(vinyl acetate)
units.
[0232] There is a continuing effort to increase the range of
monomers that are polymerized by ATRP and while (meth)acrylamides
have been polymerized earlier the polymerizations were not fully
controlled. (Meth)acrylamide polymers are biocompatible, non-toxic,
water soluble materials that find application in medicine, the food
industry and agriculture. There have been recent attempts to
develop controlled polymerization processes for these monomers
including efforts at anionic polymerization and other controlled
radical processes. A series of experiments are reported in the
Experimental Section which demonstrate that the ligand to be used
for the polymerization of (meth)acrylamides should be pure and that
final conversion of monomer to polymer is dependant on the amount
of catalyst added to the system. These results show that with the
catalyst systems described the limiting conversion first depends on
the catalyst to initiator ratio. This is tentatively attributed to
the displacement of the ligand by the polymer deactivating the
catalyst.
[0233] We have determined that controlled radical polymerization of
(meth)acrylamides can be conducted using a transition metal complex
with Me6TREN as ligand. With this system it is possible to obtain a
PDI below 1.1 but for any given catalyst level there is a
limitation on the conversion attained. However, conversions above
80% can be obtained. The level of conversion attainable in a given
system is sensitive to solvent employed, where more polar solvents
decrease the limiting conversion. The molecular weights increase
linearly with conversion and block copolymers are prepared from
macroinitiators.
Experimental Section
[0234] Having generally described this invention, a further
understanding can be gained through reference to certain specific
examples which are provided herein for purposes of illustration and
are not intended to be limiting unless otherwise specified.
[0235] Materials.
[0236] Styrene, methyl methacrylate (MMA) and methyl acrylate (MA)
were vacuum distilled from CaH.sub.2 and stored at -15.degree. C.
The onium salts, all from Aldrich, were dried under vacuum at
90.degree. C. for at least 8 h and kept in a dessicator over
anhydrous CaCl.sub.2. Iron(II) bromide and iron(III) bromide, from
Aldrich, were used as received. 1 -Phenylethylbromide (PEBr),
methyl 2-bromopropionate (MBP) and ethyl 2-bromoisobutyrate (EBiB),
from Aldrich, were used as received. AIBN was recrystallized from
methanol at 50.degree. C. and stored in the freezer. All the
solvents were used without further purification. In many cases,
monomers and solvents were bubbled with argon for at least 15 min.
immediately before polymerization.
[0237] Polymerizations.
[0238] Single-point experiments. A glass tube was loaded with the
solid compounds (FeBr.sub.2/onium salt or FeBr.sub.3/onium
salt/AIBN), capped with a rubber septum and cycled 3 times between
vacuum and argon in order to remove oxygen. Then, all liquid
components (monomer, solvent GC standard, initiator), previously
degassed, were added via syringe. The tube was sealed under argon
and placed in an oil bath and the thermostat was set at the desired
temperature. After a certain time interval, the tube was cooled,
opened and the contents dissolved in THF or toluene.
[0239] Kinetic experiments. A Schlenk flask was charged with
FeBr.sub.2 and the onium salts. The flask was sealed with a rubber
septum and was cycled 3 times between vacuum and argon. The
degassed liquid components, except for the initiator, were added
through degassed syringes, and the mixture was stirred at room
temperature until the catalytic complex formed. In the case of MA,
the initiator was added and the reaction mixture was quickly
transferred into tubes, which were immediately sealed and placed in
the oil bath. In the case of styrene and MMA, the flask was placed
in the oil bath and the initiator added. After certain time
intervals, tubes were removed from the oil bath and processed as
described above, or samples were withdrawn from the reaction
mixture using de-gassed syringes and dissolved in THF or toluene.
In the case of "reverse" ATRP, AIBN was loaded into the Schlenk
flask together with FeBr.sub.3 and the onium salt.
[0240] Measurements.
[0241] Monomer conversion was determined by GC in THF (styrene,
MMA) or toluene (MA) solution using chlorobenzene or o-xylene as
internal standards. A Shimadzu GC-14 gas chromatograph equipped
with a J&W Scientific DB-WAX column with a Shimadzu CR501
Chromatapac was used. Molecular weights and polydispersities
(M.sub.w/M.sub.n) were measured by GPC in THF using a Waters 717
Plus autosampler, PSS guard, 10.sub.5 .ANG., 1000 .ANG. and 100
.ANG. columns and a Waters 410 differential refractometer.
EXAMPLE 1
Styrene
[0242] Polymerizations were carried out according to the invention
using different molar ratios of FeBr.sub.2/onium salt (Table 1) and
showed that the reaction is slow and the rate decreasing with
increasing amounts of salt. The molecular weights agreed well with
the theoretical values, and the polydispersities were below 1.2 in
all cases. In the case of the salt/FeBr.sub.2 having a molar ratio
of 0.5, a cationic polymerization seemed to occur, leading to much
lower molecular weights and a bimodal molecular weight
distribution. Tetrabutylammonium bromide (TBABr) and
tetrabutylphosphonium bromide (TBPBr) were employed as salts. In
both cases, the optimum molar ratio of FeBr.sub.2/salt was in the
range of 1-1.5. The reaction mixture was heterogeneous at both room
temperature and 110.degree. C.
1TABLE 1 Styrene polymerization catalyzed by FeBr.sub.2/onium salts
Salt FeBr.sub.2/salt Conv. % M.sub.n,th M.sub.n,.sub.SEC
M.sub.w/M.sub.n TBABr 1/0.5 27.5 5500 2570 1.53 TBABr 1/1 23.3 4660
4670 1.18 TBABr 1/1.5 18.7 3740 4000 1.11 TBABr 1/2 11.9 2380 2460
1.18 TBPBr 1/0.5 70.0 14000 3030 2.18 TBPBr 1/1 29.3 5860 5450 1.18
TBPBr 1/1.5 16.3 3260 3240 1.10 TBPBr 1/2 5.5 1100 1050 1.15 Exp.
cond.: bulk polymerization; styrene:1-phenylethyl
bromide:Br:FeBr.sub.2 = 192:1:1; 110 C.; 7 hr.
[0243] A kinetic experiment carried out at a ratio
FeBr.sub.2/TBABr=1/1.5 showed a nonlinear kinetic plot, but good
agreement between the theoretical and experimental M.sub.ns and
polydipersities falling between 1.1 and 1.2 (FIGS. 10 and 11).
EXAMPLE 1A
Styrene Polymerization with the Catalytic System
FeBr.sub.2/TBAB/Bu.sub.3P
[0244] The formation of some polyiron complexes with a lower
reactivity during the polymerization, detailed above, can be an
explanation for the slow reaction rate. The following experiment
was conducted to determine if such complexes would be destroyed by
adding Bu.sub.3P and the polymerization would become faster (Table
1A).
2TABLE 1A Styrene polymerization with the system
FeBr.sub.2/TBAB/Bu.sub.3P Exp. FeBr.sub.2/Bu.sub.3P Conv (%)
M.sub.n,th M.sub.n M.sub.w/M.sub.n F29-1 1/0.25 48.2 9640 8800 1.28
2 1/0.5 47.2 9440 9640 1.17 3 1/0.75 56.6 11320 11040 1.24 4 1/1
58.5 11700 11830 1.21 5 1/1.5 68.6 13720 15410 1.27 Exp. cond.:
bulk, target M.sub.n = 20K; 110.degree. C.; time 20 hrs;
PEBr/FeBr.sub.2/TBAB = 1/1/1.5.
[0245] The results showed that the reaction rate did increase, by
adding Bu.sub.3P. The increase noticed may be due to the formation
of the complex between FeBr.sub.2 and Bu.sub.3P, which is known to
promote a much faster polymerization reaction.
EXAMPLE 2
Methyl Methacrylate
[0246] Polymerizations were carried out according to the invention
at different molar ratios of TBPBr/FeBr.sub.2 in xylene at
80.degree. C. and showed an optimum ratio of around 0.5-1. The
results of the kinetic experiment performed under these conditions
are shown in FIGS. 12 and 13. The reaction was fast (80% conversion
after 5 hr.), but the first-order kinetic plot was not linear,
possibly indicating the presence of termination reactions. The
molecular weights increased linearly with conversion, but they were
higher than the theoretical values. Polydispersity decreased at the
beginning of the reaction until a minimum value of 1.34 was
reached, and increased again after 60% conversion.
EXAMPLE 3
Methyl Acrylate
[0247] Single-point polymerizations were carried out according to
the invention and showed that FeBr.sub.2 complexes with chlorine,
bromine or iodine anions are active in methyl acrylate ATRP (Table
2). The experimental molecular weights agreed well with the
theoretical values, and the polydispersities were low, indicating a
controlled process. The polydispersity indices varied with the
nature of the complexing halide anion in the order
Cl.sup.->Br.sup.->I.sup.-. In addition, the polydispersity
was lower for the tetrabutylphosphonium salt than for its
tetrabutylammonium counterpart, which is possibly due to a better
solubility of the former. Similar results were obtained in the case
of butyl acrylate.
3TABLE 2 Methyl acrylate polymerization catalyzed by
FeBr.sub.2/onium salts Salt FeBr.sub.2/salt Time (hr) Conv. %
M.sub.n,th M.sub.n,SEC M.sub.w/M.sub.n TBACl 1/0.5 8.5 5 1000 1150
1.53 TBACl 1/1 8.5 16.2 3240 3960 1.39 TBACl 1/1.5 8.5 34.1 6820
8060 1.90 TBACl 1/2 8.5 29.2 5840 12400 1.92 TBABr 1/0.5 22.17 5.3
1060 1230 1.35 TBABr 1/1 22.17 22 4400 4620 1.34 TBABr 1/1.5 22.17
32.4 6480 6830 1.22 TBABr 1/2 22.17 34.5 6900 6800 1.69 TBAI 1/0.5
22 3.6 720 750 1.17 TBAI 1/1 22 13 2600 2700 1.17 TBAI 1/1.5 22
24.6 4920 5120 1.15 TBAI 1/2 22 16 3200 3510 1.12 TBAI 1/2.5 22
19.3 3860 3720 1.13 TBPBr 1/0.5 23.17 4 800 1200 1.30 TBPBr 1/1
23.17 23.8 4760 4820 1.21 TBPBr 1/1.5 23.17 27.4 5480 5980 1.20
TBPBr 1/2 23.17 32.3 6460 6680 1.23 TBPBr 1/2.5 23.17 14.4 2880
2590 1.52 Exp. cond.: bulk polymerization; MA:MBP:FeBr.sub.2 =
232.5:1:1; 90 C.
[0248] A kinetic experiment carried out at a ratio
FeBr.sub.2/TBPBr=1/1.5 showed that the methyl acrylate reaction is
very slow, and the first-order kinetic plot is nonlinear (FIG. 14).
The molecular weights agreed very well with the theoretical values,
and the polydispersities decreased with conversion to values as low
as 1.15 (FIG. 15).
[0249] The results from Examples 1-3 show that halide anions can be
used as complexing ligands in iron-mediated ATRP. Iron (II) bromide
complexed with either chlorine, bromine or iodine anion can
polymerize both styrene and (meth)acrylates in a controlled way and
achieve predetermined molecular weights and low polydispersities.
However, the first-order kinetic plot was nonlinear, possibly
indicating either the presence of termination reactions or the
modification of the catalyst structure to a complex with a lower
activity. Also, in the case of styrene and acrylates, the
polymerization was slow, whereas for MMA it was quite fast.
EXAMPLE 4
"Reverse" ATRP with Transition Metal Salts
[0250] To demonstrate the general nature of the use of transition
metal salts in "reverse" ATRP reactions the reaction was run using
ferric salts and three different monomers to exemplify the nature
of the reaction.
[0251] 4a) Methyl Methacrylate
[0252] The experimental conditions initially employed and results
obtained are shown in Table 3.
4TABLE 3 "Reverse" ATRP of MMA at 85.degree. C. FeBr.sub.3/ Exp.
TBPB Conv. % M.sub.n,th M.sub.n,SEC M.sub.w/M.sub.n Remarks FM14-1
1/0.5 11 3300 4800 1.87 hetero- geneous 14-2 1/1 58.6 17580 30600
1.63 homo- geneous 14-3 1/1.5 51.5 15450 28200 1.61 homo- geneous
14-4 1/2 13.3 3990 8700 1.31 homo- geneous 14-5 1/2.5 5 1500 2630
1.35 homo- geneous Exp. cond.: MMA/o-dichlorobenzene = 1/1 v/v;
target M.sub.n = 30K; FeBr.sub.3/AIBN = 4/1; temp. = 85.degree. C.;
reaction time = 2 hr. TBPB = tetrabutylphosphonium bromide.
M.sub.n,th = [MMA].sub.o/2/[AIBN].sub.o .times. MW.sub.MMA .times.
conversion
[0253] The obtained MWs were much higher that the theoretical
values (about double). This can be attributed to the incomplete
decomposition of AIBN. At 85.degree. C. the half lifetime of AIBN
is about 55 min. Also, the increasing viscosity of the reaction
mixture enhances the cage effect, leading to a lower yield of
primary radicals. Based on the ratio FeBr.sub.3/TBPB, it seems that
FeBr.sub.4.sup.-, is a poorer deactivator than FeBr.sub.5.sup.2-
(expts 14-2-3 vs. expts. 14-4-5).
[0254] In order to have a faster decomposition of AIBN and to
reduce the cage effect, temperature was increased to 100.degree. C.
(AIBN half lifetime about 10 min). The dilution was also increased.
The results are shown in Table 4.
5TABLE 4 "Reverse" ATRP of MMA at 100.degree. C. FeBr.sub.3/ Exp.
TBPB Conv. % M.sub.n,th M.sub.n,SEC M.sub.w/M.sub.n Remarks FM15-1
1/0.5 40.5 12150 13330 1.43 red second phase on the tube wall 15-2
1/1 63.4 19020 20110 1.65 red second phase on the tube wall 15-3
1/1.5 62.8 18840 21210 1.62 red second phase on the tube wall 15-4
1/2 38.4 11520 13650 1.30 red second phase on the tube wall 15-5
1/2.5 25.5 7650 9510 1.30 red second phase on the tube wall Exp.
cond.: MMA/o-xylene = 1/2 v/v; target M.sub.n = 30K;
FeBr.sub.3/AIBN = 4/1; temp. = 100.degree. C.; reaction time = 2.17
hr. TBPB = tetrabutylphosphonium bromide.
[0255] A much better agreement between the experimental and
theoretical M.sub.n's was obtained in this case. Again, the lowest
polydispersity was obtained when the ratio salt/FeBr.sub.3 was
higher than 2.
[0256] Using the conditions employed in experiment FM15-4, a
kinetic experiment was run. The results are displayed in FIGS. 16
and 17.
[0257] GPC traces of pMMA obtained by "reverse" ATRP show curvature
in the first order kinetic plot indicating that termination
occurred during the polymerization (FIG. 7). Due to these
termination reactions, tailing could be seen on the GPC traces and
the MW are higher than the theoretical values by about 10-15%.
Polydispersity is about 1.3 at low conversion then it increases up
to about 1.45 (FIG. 8).
[0258] 4b) Methyl Acrylate
[0259] The results of the "reverse" ATRP of methyl acrylate are
shown in Table 5.
6TABLE 5 "Reverse" ATRP of MA at 100.degree. C. FeBr.sub.3/ Exp.
TBPB Conv. % H.sub.n,th M.sub.n,SEC M.sub.w/M.sub.n Remarks FA24-1
1/0.5 3 600 480 1.11 hetero- geneous 24-2 1/1 10 2000 3400 1.84
hetero- geneous 24-3 1/1.5 23 4600 5980 1.67 hetero- geneous 24-4
1/2 26.2 5240 7500 1.31 hetero- geneous 24-5 1/2.5 29.5 5900 7350
1.30 hetero- geneous Exp. cond.: bulk; target M.sub.n = 20K;
FeBr.sub.3/AIBN = 4/1; temp. = 100.degree. C.; reaction time = 22
hr.
[0260] As in the case of direct ATRP of styrene with transition
metal salts, the polymerization is slow, similar conversions being
obtained after similar reaction times. In addition, as was
determined for the polymerization of MMA, the lowest
polydispersities are obtained for FeBr.sub.3/TBPB ratios higher
than 2.
[0261] 4c) Styrene
[0262] The reaction conditions and results are displayed in Table
6.
7TABLE 6 "Reverse" ATRP of styrene FeBr.sub.3/ Exp. TBAB Conv. %
M.sub.n,th M.sub.n,SEC M.sub.w/M.sub.n Remarks F34-1 1/0.5 53.5
10700 1700 3.7 hetero- geneous (a second red layer) 34-2 1/1 42.0
8400 2400 4.27 hetero- geneous (a second red layer) 34-3 1/1.5 31.1
6220 1980 5.17 hetero- geneous (a second red layer) 34-4 1/2 25.5
5100 1860 6.73 hetero- geneous (a second red layer) 34-5 1/2.5 37
7400 2420 5.30 hetero- geneous (a second red layer) Exp. cond.:
bulk; target M.sub.n = 20K; FeBr.sub.3/AIBN = 4/1; temp. =
110.degree. C.; reaction time = 15 hr.
[0263] TBAB=tetrabutylammonium bromide.
[0264] The results show that an uncontrolled cationic
polymerization occurred due to the presence of FeBr.sub.3. The
experiment should be redone by adding the monomer to the preformed
complex.
EXAMPLE 5
MMA Polymerization with FeBr.sub.2/Onium Salts, Initiated by
2-bromo-isobutyric Acid.
[0265] A single tube experiment was performed under the following
conditions: MMA/o-xylene=1/1 v/v; target M.sub.n=40K;
2-Br-isobutyric acid/FeBr.sub.2/TBPB=0.75/1/1; temp.=80.degree. C.;
time=2.25 hr. The results were: conversion=42%; M.sub.n,th=16800;
M.sub.n,SEC=25550; M.sub.w/M.sub.n=1.29. The initiator efficiency
calculated based on these data is 66%. After a comparison of these
results with the results obtained above for MMA polymerization
performed under similar conditions and initiated by ethyl 2-bromo
isobutyrate one may conclude that the polymerization is not too
affected by the free carboxylic initiator.
EXAMPLE 6
MMA Copolymerization with Methacrylic Acid
[0266] A copolymerization experiment of MMA with methacrylic acid
(5 mole-%) was attempted. The reaction was carried out in
o-dichlorobenzene (1/1 v/v vs. MMA), target M.sub.n=30K, at
80.degree. C., for 21.5 hr, under nitrogen. The initiating system
was EBiB:FeBr.sub.2:TBPB=1:1:1. The catalyst was prepared first at
room temperature in DCB+MMA, then degassed methacrylic acid was
added, and finally EBiB. Samples were withdrawn from the reaction
mixture at different time intervals in order to measure conversion.
The final molecular weight and polydispersity were measured on both
THF and DMF lines. The samples were processed in the usual way
(passed through an alumina column). The results are shown in Table
7.
8TABLE 7 Copolymerization of MMA and MAc using FeBr.sub.2/salts
Time Conv. MMA hr % Conv. MAc M.sub.n M.sub.w/M.sub.n 5.33 16.6
11.3 -- -- 21.5 25.4 11.8 3520* 1.91* 4660** 1.61** *THF line, PMMA
standards; **DMF line, PMMA standards.
[0267] The results from the THF line are affected by the presence
of an impurity, whose peak overlap with the polymer peak.
EXAMPLE 7
Use of Counterion Supported Catalysts and Counterion Exchange for
Catalyst Recycle
[0268] The following examples are provided to better illustrate the
present invention of supporting the catalyst through use of a
shared counterion by exemplifying the use of a transition metal
catalyst supported on DOWEX.TM. sodium exchange resins for
polymerization of methyl acrylate, and are not intended to be
limiting. Most commercially available cationic ion exchange resins
consist of sulfonated crosslinked polystyrene-divinylbenzene beads.
Cations are typically H.sup.+, Na.sup.+ or a mixture of the two and
the anionic counter ion is a sulfonyl group. The exchange of ATRP
active copper complexes with Na.sup.+ is much slower than with
H.sup.+, presumably due to the difference in cation size. Na.sup.+
sites on the ion exchange resins can be converted to H.sup.+ sites
by treatment with strong mineral acid such as HNO.sub.3 or HCl.
Effective removal of the Cu(I) and Cu(II) ATRP active complexes can
be achieved using large excess of ion exchange resins, i.e. excess
of accessible H.sup.+ sites. In that case, the above equilibrium
shifts to the right favoring the complete removal of the copper
complex from the solution. Due to the colored nature of the Cu(I)
and Cu(II) complexes employed in ATRP, UV-Vis spectrometry was used
to monitor their concentration in solution.
[0269] Materials.
[0270] CuBr (99.999%, Aldrich), CuBr.sub.2 (99.999%) and
2,2'-bipyridine (99+%, Aldrich) were stored in glove box under
nitrogen atmosphere. DOWEX MSC-1 macroporous ion-exchange resins
(20-50 mesh, Aldrich) were washed with deionized H.sub.2O, acetone,
and dried under vacuum for 48 h.
N,N,N',N",N"-Pentamethyldiethylenetriamine (99%, Aldrich),
Tris-(2-dimethylaminoehtyl)amine (synthesized according to well
known literature methods) and all solvents were distilled and
deoxigenized prior to usage.
[0271] UV-VIS Measurements.
[0272] The spectroscopic measurements were performed on a
UV/VIS/NIR spectrometer Lambda 900 (Perkin Elmer), using either a
quartz UV cell or a quartz UV cell joined to a Schlenk flask. All
samples were taken out of the reaction mixtures in the absence of
oxygen, but were exposed to air for 2 h prior to dilution with
methanol and UV-VIS analysis. Blank solutions were prepared by
mixing 0.5 mL of the reaction solvent with 4.5 mL of methanol.
[0273] Loading Capacity of DOWEX MSC-1 Macroporous Ion-Exchange
Resins in the Dry H.sup.+ Form.
[0274] In a typical experiment, 5.0 g of DOWEX.TM. MSC-1
macroporous ion-exchange resins were transformed into the H.sup.+
form by slow treatment with 500 mL of 1.6 M HNO.sub.3.
Subsequently, the resins were washed to neutrality with distilled
water, suction-filtered and dried in air. Resins were then dried in
a vacuum oven for 24 h to remove any residual H.sub.2O. Dry resins
(0.7274 g) were weighed into a 200 mL Erlenmeyer flask and allowed
to stand 24 h with 100 mL of 0.1 M NaOH in 5% NaCl solution. 20.0
mL of the solution were then back titrated with 0.1 M
H.sub.2SO.sub.4. 6.2 mL of acid was required to neutralize the
solution of NaOH. Loading capacity of the resins in the dry H.sup.+
form was then calculated, based on the original and final amount of
NaOH in the solution, to be 5.2.times.10.sup.-3 mol of Na.sup.+/g
of resins in the dry H.sup.+ form.
[0275] Loading Capacity of DOWEX MSC-1 Macroporous Ion-Exchange
Resins in the Crude Form.
[0276] The same procedure was used as above with the exception that
DOWEX.TM. MSC-1 macroporous ion-exchange resins were not treated
with excess HNO.sub.3 prior to the reaction with NaOH. Loading
capacity was calculated to be 5.0.times.10.sup.-3 mol of Na.sup.+/g
of resins in the crude form.
[0277] Kinetic Studies of Catalyst Removal.
[0278] In a typical experiment, 0.0347 g (2.420.times.10.sup.-4
mol) of CuBr and 0.05052 mL (2.420.times.10.sup.-4 mol) of
N,N,N',N",N"-Pentamethyldiethylenetriamine were placed in a Schlenk
flask and 20.0 mL of solvent added (methyl acrylate, chlorobenzene,
ethanol, acetone or different ratios of methyl acrylate and
chlorobenzene and methyl acrylate and acetone). Mixture was stirred
at room temperature for three hours to allow full complex
formation. It was then transferred (via cannula) to 0.815 g of
DOWEX.TM. MSC-1 macroporous ion-exchange resins. Samples were taken
out of the mixture (0.5 mL ) at different time intervals, exposed
to air, and diluted to 5.0 mL with methanol prior to UV/VIS
analysis. Concentrations were calculated based on Beer-Lambert's
plot for the oxidized form of
CuBr/[N,N,N',N",N"-Pentamethyldiethylenetri- amine] in methanol
(.lambda..sub.max=652 nm, .epsilon.=143.22 Lmol.sup.-1cm.sup.-1,
R.sup.2=0.9998). The same experimental procedure was also used for
other Cu(I) and Cu(II) complexes. Concentrations were determined
based on the corresponding Beer-Lambert's plots.
[0279] When a solution of CuBr/PMDETA is brought into contact with
DOWEX.TM. MSC-1 ion-exchange resins, it slowly decolorizes and
becomes acidic. This observation is consistent with the following
cationic ion-exchange equilibrium: 17
[0280] The position of the equilibrium is dependent on the polarity
of the solvent, ionic character of the exchanging complex, pH of
the solution, the degree of crosslinking, acidic strength and size
of the ion-exchange resins. These factors are very important when
considering maximizing removing capacity of ion-exchange resins
towards Cu(I) complex. In particular, pH of the solution plays very
important role. At lower pH values, protonation of PMDETA will
occur which causes decomposition of the copper(I) complex. Also, on
the other hand, exchange of CuBr/PMDETA with Na.sup.+ is much
slower than with H.sup.+ due to the difference in cation size.
Na.sup.+ sites on the DOWEX MSC-1 resins (Scheme 3) can be
converted to H.sup.+ sites by treatment with strong mineral acid
such as HNO.sub.3 or HCl, which is a typical procedure when
determining maximum loading capacity of the resins. However, these
problems can be avoided by using large excess of ion-exchange
resins relative to the concentration of CuBr/PMDETA. In that case,
the above equilibrium shifts to the right which favors the complete
removal of CuBr/PMDETA from the solution.
[0281] FIG. 1 shows the effect of the solvent on the removal of
CuBr/PMDETA using DOWEX MSC-1 macroporous ion exchange resins. From
the figure, it is apparent that solvent had little effect on the
rate of removal of the Cu(I) complex from either methyl acrylate,
methyl acrylate/chlorobenzene mixtures or ethanol. In fact, using
20.0 mL of 1.2.times.10.sup.-2 molL.sup.-1 of CuBr/PMDETA
(2.420.times.10.sup.-4 mol) and 0.815 g of resins, it took
approximately 60 min to remove more than 95% of the complex from
the solution. Part of the solvent independence on the rate of
removal lies in the fact that excess of H.sup.+ sites on the resins
were used (4.075.times.10.sup.-3 mol, 17 eq.) relative to the
amount of CuBr/PMDETA in solution, which shifted the equilibrium
(Eq. 1) to the right. The rate of removal of CuBr/PMDETA became
solvent dependent, and increased as solvent polarity increased,
when the amount of H.sup.+ relative to the CuBr/PMDETA was reduced
below 5 equivalents.
[0282] In FIG. 2 is shown temperature effect on the removal of
CuBr/PMDETA from a 50% methyl acrylate/50% chlorobenzene solution.
The rate of removal increased with temperature. At temperatures
above 50.degree. C. it took approximately 20 min to remove more
than 95% of CuBr/PMDETA from the solution. Similar results were
also obtained using methyl acrylate and acetone or THF
mixtures.
[0283] FIG. 3 shows the effect of the solvent on the removal of
CuBr.sub.2/PMDETA using DOWEX MSC-1 ion-exchange resins. Studies
were performed at much lower concentrations when compared to
CuBr/PMDETA due to the limited solubility of Cu(II) complex. The
rate of the removal was dependent on the polarity of the solvent
and generally increased as the solvent polarity increased. When
comparing Cu(I) and Cu(II) complexes with PMDETA under the same
experimental conditions (FIGS. 1 and 3) it can be seen that the
rates of removal are comparable.
[0284] The effect on the removal of CuBr/PMDETA using different
types of ion exchange resins is presented in FIG. 4. The exchange
was the fastest with macroporous resins, and was also depended on
the degree of crosslinking of polystyrene and bead size. For the
same bead size, the rate of removal of CuBr/PMDETA or
CuBr.sub.2/PMDETA decreased as the degree of crosslinking
increased. Presumably, this was due to swelling effect of the resin
polymer network, allowing for the copper salts to gain access to
the sulfonated sites in the interior of the beads.
[0285] The rate of catalyst removal from an acetone/methyl acrylate
mixture was found to be dependent upon the ligands used to complex
the catalyst, FIG. 5. It was found that the removal was fastest
with CuBr/PMDETA and slowest with CuBr/2bpy. The ionic character of
these complexes and their structures in solution are not precisely
known, and hence no definitive conclusions can be drawn as to why
they show different behavior when exchanging with H.sup.+ sites on
the ion exchange resins. For Cu(II) complexes we also found that
the amount of Br released to the solution depended on the ligand
used. This effect was presumably due to the differences in the
overall charge of the Cu(II) center, which depending on the ligand
used can be +1 or +2.
[0286] These experiments demonstrate an efficient method for the
removal of Cu(I) and Cu(II) complexes in ATRP using ion exchange
resins with acidic groups. The utility of these resins to remove
copper catalysts from bulk (monomer and solvent), polymerization
and organic solutions has also been defined. The resins have also
been used to remove catalyst from ATRP water-borne polymerizations
without coagulation of the polymer latex. It was found that the
rate of removal of copper complexes is dependent on the solvent
polarity, temperature, type of ion exchange resins used and ionic
character and size of the copper complex. In the limit of using
large excess of H.sup.+ sites on the resins, Cu(I) and Cu(II)
complexes can be removed from reaction mixtures relatively fast. It
is envisioned that the copper complexes can be recycled by the use
of ion exchange resins as well.
EXAMPLE 8
[0287] A DOWEX.TM. sodium exchange resin was loaded with Cu(I) and
complexed with Me6TREN. Methyl acrylate and MBP initiator was added
and the flask placed in an oil bath at 60.degree. C. The experiment
employed the following conditions: MA:MBP:Cu(I) on resins=500:1:10.
The reaction was extremely fast and the solution became viscous
within 5 min stirring. The product was dissolved in THF and
separated from the resin. The GPC trace indicated the presence of a
polymer with M.sub.n=38100 g/mol, M.sub.w=43770 g/mol, PDI=1.15
(theoretical, for 99% conversion is 43030 g/mol).
EXAMPLE 9
[0288] The resins from example 8, were used again for the same
reaction, but at room temperature. This time, the solution became
extremely viscous (stirring stops) after 3 h. The polymer had the
expected low molecular weight peak, but also a higher molecular
weight peak. This was attributed to poor stirring. We believe that
if the reactions are not fast the reactions cannot be done in bulk
since coupling of the chains can occur at higher conversions
(starting even at 50%), because radical chains find it difficult to
reach Cu(II) to abstract Br back, and so they couple. (As noted
elsewhere in the application this phenomenon can be addressed by
increasing the concentration of Cu(II) on the support.)
EXAMPLE 10
[0289] The resin from example 9 was reused once more. The
conditions were as follows: MA:MBP:Cu(I) on the resins=1000:1:10.
The objective was to use more monomer in order to reduce the rate
of reaction and be able to watch the reaction, because it will now
take more time. Again, after 50 min stirring at 60.degree. C. the
mixture became extremely viscous. The resulting polymer has the
expected low molecular weight peak (20,000 g/mol) but also a much
higher molecular weight peak (900,000). This is indicative of some
redox initiated polymerization at low conversion prior to forming a
Cu(I)/Cu(II) equilibrium in the catalyst system.
EXAMPLE 11
[0290] The reaction was run using benzene as solvent, again using
the same resin/catalyst. The ratio of reactants was MA:MBP:Cu(I) on
resins: benzene=1000:1:10:3000, and the reaction was run at
60.degree. C. The rate of reaction was followed by GC to examine at
the kinetics. The results show that it is a "living" system with
linear increase in molecular weight with conversion.
[0291] The results from examples 8-11 show that a transition metal
supported on commercially available ion exchange resins show the
same activity in repeat experiments and that they can be used over
and over. This indicates that a transition metal catalyst for ATRP
polymerization can be supported on a solid support through a
"shared" counterion, one directly attached to the support, and that
the catalyst can be used in a batch or continuous polymerization
system.
[0292] In examples 8-11, Cu(CH.sub.3CN).sub.4PF.sub.6 was the
source of Cu+ on the resins. The supported Cu(I) is later complexed
with Me6TREN.
EXAMPLE 12
Supported Transition Metal Salt-Mediated ATRP
[0293] The following experiments performed were intended to check
the possibility of conducting an ATRP reaction using supporting
FeBr.sub.3 on anion exchange resins. These initial examples are
followed by the use of the supported catalyst in the "reverse" ATRP
of MMA.
[0294] Two types of ion exchange resins were used to support the
transition metal salts:
[0295] DOWEX 1.times.8-400 chloride--which is a gel type resins
with 200-400 meshes bead size and has chloride as the exchangeable
anion;
[0296] DOWEX MSA-1--which is a macroporous type resin with 20-50
meshes bead size.
[0297] The commercial product also has chloride as exchangeable
anion.
[0298] One experiment was done with the resin in chloride form. For
the second experiment, the resin was converted into bromide form,
by loading it into a column, passing a aqueous solution of NaBr
through the column, washing with deionized water and methanol, and
dried under high vacuum.
[0299] Generally a loading capacity of 5.times.10.sup.-4 meq/g was
assumed for the resins. This was about 3 times lower than the
loading capacity described in literature for this type of resins
under standard use (anion exchange). The loading procedure was as
follows: 1 g dry resin, 0.15 g (5.times.10.sup.-4 mole) FeBr.sub.3
and 10 ml o-dichlorobenzene were loaded in a Schlenk flask. The
mixture was stirred under nitrogen at room temperature for more
than 20 hr. Then the resins were recovered by filtration with
suction, washed with 100% ethanol and dried under vacuum. When
chloride-form resins were used, the color of the final product was
yellow. In the case of bromide-form resins the color was maroon.
Based on the color change, one can conclude that the
FeX.sub.4.sup.- complex anion is formed on the surface of the
resins, even though not all FeBr.sub.3 added was absorbed on to the
resin. Based on visual observation, more complex formed in case of
macroporous resins, as would be expected.
[0300] Literature data show that FeCl.sub.4.sup.- anion is yellow
and FeBr.sub.4.sup.- is brown. The yellow color of the beads shows
that Cl and Br anions exchange very fast in FeX.sub.4.sup.-.
[0301] Two experiments were carried out in order to demonstrate the
activity of the supported catalysts in the "reverse" ATRP of
MMA.
EXAMPLE 12a. (FM18R)
[0302] The following conditions were used: temp.=100.degree. C.;
MMA/dichlorobenzene=1/2; target M.sub.n=30K. The target M.sub.n was
calculated using the following relationship:
M.sub.n=[MMA].sub.o/2/[AIBN]- .sub.o.times.MW.sub.MMA.times.C %. A
FeBr.sub.3/AIBN of 6/1 was aimed, assuming that all FeBr.sub.3 used
in the reaction with the resins was supported. The actual amounts
used were: MMA=1.5 ml; DCB=3 ml; FeBr.sub.3=41 mg; AIBN=4 mg;
macroporous resins--bromide form=0.4 g.
[0303] In a Schlenk flask fitted with condenser and stir bar AIBN
and resins were loaded. After three vacuum-nitrogen cycles,
degassed MMA and DCB were added via degassed syringes, and the
reaction flask was placed in an oil bath kept at 100.degree. C. the
stirring rate was about 1000 rpm. At time intervals samples were
withdrawn from the flask, and the conversion was checked by GC,
using DCB as internal standard. Because of the size of the resins,
the beads were not uniformly dispersed in the reaction mixture.
After the viscosity of the reaction mixture increased, the mixing
became even worse. At the final, the liquid phase was colorless.
The results are shown in Table 8.
9TABLE 8 "Reverse" ATRP of MMA catalyzed by FeBr.sub.3 supported on
macroporous resins Reaction Conversion Sample time (hr) (%) M.sub.n
M.sub.w/M.sub.n M.sub.P 1 0.5 52 26800 2.26 70150 2 1.5 64.2 20300
2.75 65300 3 4 71.6 28600 2.01 65300 4 7 88.1 29600 1.97 67400 5 21
95.6 31000 1.86 65100
EXAMPLE 12b. (FM 19R.)
[0304] Same conditions as in exp. FM 18R were employed except for
0.87 g of gel type resins (chloride) were used. The beads were
homogeneously dispersed at the beginning of the reaction, but the
mixing became bad after the viscosity of the reaction mixture
increased. The results are shown in Table 9.
10TABLE 9 "Reverse" ATRP of MMA catalyzed by FeBr.sub.3 supported
on gel type resin. Reaction time Conversion Sample (hr) (%) M.sub.n
M.sub.w/M.sub.n 1 0.5 53 29800 2.04 2 1.5 63.6 32600 2.24 3 3.5
68.1 35400 2.24 4 8 71.7 35500 2.26 5 21 82.2 36000 2.19
[0305] In both of these initial experiments the results look more
like a dead-end polymerization. It seems that no
deactivation-activation cycle occurred and the supported complex
has to be modified to increase the concentration of the redox
conjugate.
EXAMPLE 13
Precipitation Polymerization
[0306] The concept behind these experiments were that besides
supported catalyst and fluorinated solvents, another approach to
recycle the ATRP catalyst would be the use of a solvent which
dissolves the polymer at the polymerization temperature, but the
polymer precipitates out at room temperature (or below). The
polymer is recovered by filtration, and the filtrate containing the
dissolved catalyst is recycled.
[0307] 13a) Alcohols as Solvents
[0308] Methanol and absolute ethanol were used as solvents for the
ATRP of MMA under the following conditions: target M.sub.n=30K;
90.degree. C.; MMA/alcohol=1/2 v/v; EBiB/CuCl/dNbpy=1/1/2; 7.16 h.
The results are shown in Table 10.
11TABLE 10 Precipitation polymerization of MMA in alcohols
Conversion Exp. Solvent % M.sub.n M.sub.w/M.sub.n P-MMA1-1 MeOH
54.7 19500 1.85 P-MMA1-2 EtOH 64.3 20400 1.64
[0309] As expected, the reaction mixture was homogeneous at
90.degree. C., however in a non-agitated rapidly cooled system by
the time the solution had cooled to room temperature the polymer
had precipitated as lump, which made it difficult to be recovered.
In addition, methanol has swelled to some degree the polymer. Use
of a less polar solvent, ethanol, afforded a lower polydispersity.
An agitated solution during cooling leads to a precipitated
powder.
[0310] 13b) Heptane as Solvent
[0311] The following conditions were employed: target M.sub.n=60K;
90.degree. C.; MMA/heptane=1/2; EBiB/CuCl/dNbpy=1/1/2; 7.16 h. The
polymer precipitated out during the polymerization.
Conversion=14-16%; M.sub.n=11400; M.sub.w/M.sub.n=1.21.
EXAMPLE 14
Coupling Reactions
[0312] The model polymer was prepared by polymerization of methyl
acrylate using ethylene glycol mono(2-bromoisobutyrate) as
initiator and cuprous
bromide/N,N,N',N",N"-pentamethyldiethylenetriamine (PMDETA) as the
transition metal catalyst. The success of the atom transfer
coupling reaction can be seen in Table 11. Use of 0.5 mole of
.alpha.-methylstyrene per mole of
.alpha.-bromo-.omega.-hydroxy-poly(meth- yl acrylate) in experiment
75NB1 shows that the number average molecular weight (Mn)
essentially doubled. The proposed mechanism of this coupling
reaction is shown in FIG. 6.
[0313] When 0.25 mole of di-isopropenyl benzene was used in the
coupling reaction, experiment 77NB1; the Mn of the polymer, after
removal of bromine, was quadrupled indicating the formation of a
four armed star polymer with four terminal hydroxy groups.
12TABLE 11 Summary of Coupling Reactions Coupling Mn MWD Ratio of
Mn MWD Exp.# Agent Base before before Chains after after 75NB1
a-Methyl styrene none 1329 1.1 2 2965 1.32 76NB1 m-di-isopropenyl
none 1329 1.1 1.9 3782 1.74 benzene 77NB1 m-di-isopropenyl none
1057 1.1 4 3856 1.69 benzene 87NB1 a-Methyl strene Triethylamine
1270 1.17 2 2448 1.44 88NB1 m-di-isopropenyl Triethylamine 1270
1.17 4 2601 2.48 benzene 89NB1 a-Methyl styrene Triethylamine 1270
1.17 2 2457 1.42 90NB1 m-di-isopropenyl Triethylamine 1270 1.17 2.3
2534 1.57 benzene 98NB1 a-Methyl styrene 2,6-Dt-Bpy 1060 1.13 2.4
2079 1.38
[0314] The above examples were provided only to illustrate the
present invention and are not meant to be limiting. Any
appropriately substituted olefin that can undergo the sequence of
controlled radical addition, dehydrohalogenation and radical
addition to the unsaturation formed by dehydrohalogenation, would
be suitable for use in the following examples.
[0315] The third technique shown in scheme 6 as route C involves
coupling of .alpha.-hydroxy-.omega.-bromo-poly(methyl acrylate) by
a coupling agent (CA in scheme 6). This polymer was prepared by
initiating methyl acrylate with ethylene glycol
mono(2-bromoisobutyrate). The polymerization was terminated at 80%
conversion, the crude reaction mixture was exposed to column
chromatography with alumina as stationary phase, and the polymer
was isolated by precipitation in hexanes. The coupling reaction was
performed by measuring the polymer and cuprous bromide in a
round-bottomed flask, the flask was sealed and purged with
nitrogen. PMDETA, the coupling agent, and benzene were added and
the reaction mixture was placed at 60.degree. C. In the case where
the coupling agent was .alpha.-methylstyrene and the ratio of
chains to .alpha.-methylstyrene (R) was two, the molecular weight
increased from 1330 g/mol to 2960 and the molecular weight
distribution increased from 1.10 to 1.32. The degree of
functionalization as determined by .sup.1H NMR was f=1.8.
[0316] If m-diisopropenylbenzene was used as the coupling agent and
the ratio of chains to m-diisopropenylbenzene (R) was four, the
molecular weight increased from 1060 to 3860 and the molecular
weight distribution increased from 1.10 to 1.69. The degree of
functionalization as determined by .sup.1H NMR was f=2.8. This
result indicates that stars are formed if the coupling is performed
with m-diisopropenylbenzene. MALDI-TOF-MS was used to tentatively
investigate the mechanism.
[0317] If a 1:1 ratio of chains to m-diisopropenylbenzene was used,
the MALDI-TOF-MS clearly showed that addition of
m-diisopropenylbenzene was followed by elimination of HBr. This
lead to the suggested mechanism shown in FIG. 7 where addition of
poly(methyl acrylate) to m-diisopropenylbenzene is followed by
reaction with cupric bromide and subsequent elimination, yielding
HBr and a terminal olefin (1). The newly formed olefin is able to
add to poly(methyl acrylate), to yield (2), which then reacts with
cupric bromide and eliminates HBr to yield the coupled product (3).
A similar addition can occur at the second double bond of the
coupling agent and the final product is a star with up to four
arms.
EXAMPLE 15
Incorporation of Functional End Groups
[0318] A hydroxy containing initiator, ethylene glycol mono(2-bromo
isobutyrate) was employed to polymerize methyl acrylate with
cuprous bromide/PMDETA catalyst system, p-dimethoxybenzene being
present as solvent. Allyl alcohol was added after 80% conversion of
monomer to polymer along with differing levels of copper zero and
additional solubilizing ligand. The experimental details listed in
Table 11 show that under appropriate conditions essentially a
"homo"-telechelic .alpha.-.omega.-dihydroxy-polymer was formed
within three hours.
13TABLE 12 Functionalization with allyl alcohol CuBr:Ligand:Cu(0):I
2*I:Allyl alcohol Time f 0:0:1:9 1:15 23 0.77 1:1:0.17:1.5 1:14 3
1.37 1:1:0.17:1.5 1.14 24 1.43 1:1:0.37:3 1:16 4.5 1.76 1:1:0.37:3
1:16 23 2 1:1:1.7:1.8 1:13 0.5 1.3 1:1:1.7:1.8 1:13 1 1.6
1:1:1.7:1.8 1:13 2 1.8 1:1:1.7:1.8 1:13 3 1.9
EXAMPLE 16
Incorporation of Vinyl Acetate
[0319] Vinyl acetate from Aldrich was distilled over CaH.sub.2 and
stored under an argon atmosphere at -15.degree. C. Fe(OAc).sub.2
(97%) was purchased from Strem Chemicals and used without further
purification. CCl.sub.4 and
N,N,N',N",N"-pentamethyldiethylenetriamine (PMDETA) were from
Aldrich, and ethyl acetate (EtOAc) (solvent) was from Fisher. They
were all used as received.
[0320] Polymerization and Characterization. A Dry Round Bottom
Flask was Charged with Fe(OAc).sub.2.
[0321] The flask was sealed with a rubber septum and was cycled
between vacuum and argon three times to remove the oxygen. Degassed
monomer, solvent and amine ligand were added using degassed
syringes. The flask was immersed in an oil bath held by a
thermostat at the desired temperature. Initiator was then added and
timing was started. At timed intervals, samples were withdrawn from
the flask using degassed syringes and added to THF. Monomer
conversion was determined from the concentration of residual
monomer using gas chromatography (GC). Molecular weights and
molecular weight distributions were measured using size exclusion
chromatography (SEC) using THF as the eluent. Polystyrene standards
were used to calibrate SEC columns.
[0322] Single-Point Experiments Indicating Controlled
Polymerization.
[0323] A series of polymerizations were carried out under standard
ATRP conditions using methyl 2-bromopropionate as the initiator and
CuBr complexed by either 2,2'-bipyridine (bpy) or
N,N,N',N",N"-pentamethyldiet- hylenetriamine (PMDETA) as the
catalyst at temperatures ranging from 50 to 110.degree. C.;
however, no formation of poly(vinyl acetate) (pVOAc) was observed.
The use of other common ATRP initiators or chlorine as the
exchanging halogen afforded similar results. The difficulty
encountered in the ATRP of VOAc may be mainly attributed to the low
equilibrium constant (K.sub.eq) as defined below. 18
[0324] Other Factors Include Possible Side Reactions Such as the
Decomposition of the Dormant Chain Ends.
[0325] Interestingly, polymers were obtained when Fe(OAc).sub.2
complexed by PMDETA was employed as a catalyst with CCl.sub.4 as
the initiator. An examination of representative size exclusion
chromatography (SEC) traces showed progressive shift towards higher
molecular weights with decreasing amount of CCl.sub.4 used.
Moreover, an almost linear relationship between the experimental
molecular weights (M.sub.n,SEC) and the theoretical values
(M.sub.n,SEC) was obtained. The theoretical values were calculated
based on the ratios of consumed monomer to initiator assuming
quantitative initiation from CCl.sub.4. In addition, polyvinyl
acetate made with the CCl.sub.4/Fe(OAc).sub.2/PMDETA initiating
system (M.sub.n=3600 and M.sub.w/M.sub.n=1.81) was used as an
efficient macroinitiator for the synthesis of block copolymers with
n-butyl acrylate (nBA) and styrene (Sty) (M.sub.n=24300 and
M.sub.w/M.sub.n=1.42) using typical ATRP catalytic systems. The
signal of the block copolymer shifted cleanly to higher molecular
weights ad polydispersity was reduced. Thus, it appeared from these
initial exemplary single-point experiments that polymerization of
VOAc with the CCl.sub.4/Fe(OAc).sub.2/- PMDETA initiating system
was controlled.
[0326] Kinetic Studies Indicating Transfer Dominated
Polymerization
[0327] Further detailed kinetic studies were carried out to gain
better insight into the polymerization. Examination of a
semilogarithmic kinetic plot of the polymerization of VOAc which
was initiated by CCl.sub.4 and promoted by the Fe(OAc).sub.2/PMDETA
complex showed that the concentration of the propagating species
were approximately constant until the polymerization reached ca.
60% monomer conversion and then polymerization rate dropped
abruptly. The molecular weight vs conversion plot shows that
polymers with high molecular weights were formed at the early stage
of the polymerization and that the experimental molecular weight
remained relatively constant throughout the reaction. In addition,
polymers with relatively high polydispersities
(M.sub.w/M.sub.n.about.1.8 to 2.0) were obtained, independent of
conversion.
[0328] Effect of Structure of Alkyl Halides and Transition Metal
Complexes
[0329] Different initiators were also examined and the results are
shown in Table 13. With CCl.sub.4 as the initiator, the formed
pVOAc had experimental molecular weight (M.sub.n,SEC=7800) close to
the theoretical value (M.sub.n,SEC=6300) which was calculated based
on the ratio of consumed monomer to initiator assuming quantitative
initiation from CCl.sub.4 without any chain transfer. Similar
result was obtained using methyl 2,2-dichloroacetate (entry 2) or
bromoform (entry 5) as the initiator. However, other initiators
either led to pVOAc with too high molecular weight or resulted in
the formation of oligomers.
EXAMPLE 17
Telomerization of Vinylacetate
[0330] The results of the experiments designed for the preparation
of polyvinyl acetate containing terminal functional groups that are
active for ATRP are summarized in Table 14.
14TABLE 13 Use of Different Initiators in the Polymerization of
VOAc Promoted by Fe(OAc).sub.2/PMDETA complex en- time conv
try.sup.a initiator (h) (%) M.sub.n,.sub.Ca1.sup.b M.sub.n,SEC
M.sub.w/M.sub.n 1 CCl.sub.4 0.4 63 6300 7800 1.8 2 CHCl.sub.3 1.2
41 4100 11900 3.5 3 CH.sub.3OC(O)CHCl.sub.2 0.2 46 4600 4300 2.4 4
CH.sub.3OC(O)CH(CH.sub.3)Cl 12.0 14 1400 117700 2.2 5 CBr.sub.4
16.2 <5 <500 olig- -- omers 6 CHBr.sub.3 16.2 22 2200 2100
2.6 7 CH.sub.3OC(O)CH(CH.sub.3)Br 12.0 35 3500 217800 1.9 8
CHI.sub.3 0.4 <5 <500 olig- -- omers .sup.aConditions:
50.degree. C.; [VOAc].sub.o = 10.8 M (bulk);
[VOAc].sub.o/[initiator].sub.o = 117;
[initiator].sub.o/[Fe(OAc).sub.2].s- ub.o/[PMDETA].sub.o = 1/1/1.
.sup.bM.sub.n,Cal = ([M].sub.o/[In].sub.o) .times. (MW).sub.o
.times. conversion, where [M].sub.o and [In].sub.o represent the
initial concentrations of monomer and initiator, and (MW).sub.o is
the molecular weight of the monomer.
EXAMPLE 18
Ligand Developments
[0331] Materials. Initiators (Aldrich) were Used as Received.
Diethylenetriamine (Aldrich) and 1-(2-aminoethyl)piperazine
(Aldrich) were Used as Received.
[0332] Polymerizations. Solids were added to 10 mL round bottomed
flask equipped with a stir bar. The flask was evacuated and back
filled with nitrogen. Liquids were degassed by 3 freeze-pump-thaw
cycles, then added to the reaction flask via syringe. The reaction
mixture was heated to the polymerization temperature, then
initiator was added via syringe.
[0333] Characterization. Conversion was measured using a Shimadzu
GC-17A against an internal standard. Molecular weights were
measured using a GPC equipped with Waters 717 Plus autosampler, PSS
SDV 10.sup.5, 10.sup.3, and 10.sup.2 .ANG. columns, and a Waters
410 RI detector against polystyrene and poly[methyl methacrylate]
standards.
EXAMPLE 18a
Polymerization of t-BA with Cu(I)/PMDETA
[0334] The polymerization of MA with Cu(I)/PMDETA initiated with
methyl 2-bromopropionate (MBrP), has been shown to be well
controlled in earlier applications. However, under the same
reaction conditions the polymerization of (t-BA) is not well
controlled. Table 15 shows the results of ATRP of (t-BA) using the
CuBr/PMDETA catalyst system and MBrP as the initiator.
[0335] Reactions initially performed in bulk at 65.degree. C. were
fast, reaching high conversion within 20 minutes (Entry 1). By
lowering the temperature and increasing the degree of
polymerization, the reaction was controlled, however, the final
polydispersity was still rather high, M.sub.w/M.sub.n=1.33, and the
rate of the reaction quite slow (Entry 2). Addition of CuBr.sub.2
improved the polydispersity, but it also decreased the rate
further. p-Dimethoxybenzene was used as a solvent and although the
reaction was well-controlled, the catalyst was not fully soluble
and the polydispersities remained higher than 1.2 (Entry 3). More
polar solvents, such as acetone or DMF, initially provided a
homogeneous catalyst system. The slower rate and lower final
polydispersities in these reactions suggest the polar solvents
improve the concentration of the deactivator in solution, which in
this case is the element necessary to achieve a controlled
polymerization.
15TABLE 14 Results for ATRP of t-BA using MBr/CuBr/PMDETA T Conv
No. Solvent (.degree. C.) Time (%) M.sub.n M.sub.w/M.sub.n 1
Bulk.sup.a 65 20 min. >95 2800 1.49 2 Bulk.sup.b RT 17 hrs. 77
5300 1.33 3 20% DMB.sup.c 60 1.25 hrs. 95 5000 1.23 4 25%
acetone.sup.c 60 5 hrs. 93 6000 1.11 5 25% DMF.sup.c 60 4.5 hrs. 93
6500 1.10 .sup.aratio of [tBA]:[MBrP]:[CuBr]:[PMDETA] =
25:1:0.25:0.25 .sup.bratio of [tBA]:[MBrP]:[CuBr]:[PMDETA] =
50:1:0.5:0.5 .sup.cratio of
[tBA]:[MBrP]:[CuBr]:[PMDETA]:[CuBr.sub.2] =
50:1:0.5:0.525:0.025
EXAMPLE 18b
Polymerization of MA with Cu/DETA
[0336] Polymerizations of MA in bulk with Cu(I), Cu(II), DETA, and
initiator (Entry 1/Table 13) showed no control of molecular weight.
Based on previous results it was anticipated that the addition of a
polar solvent would increase the solubility of the catalyst in MA
and improved polymerization control. Several reactions were
conducted using different solvents and variable dilutions, the
results of these experiments are shown in Table 15. As shown in the
table, the reaction was quite sensitive to the amount of solvent
used, and it appears that a lower concentration (5-10%) of a polar
solvent gives the best control of the reaction. As in the case of
t-BA with PMDETA, it appears that the addition of a polar solvent
increases the concentration of the deactivator in solution to give
a more controlled polymerization.
16TABLE 15 Results for ATRP of MA using MBrP/CuBr/CuBr.sub.2/DETA
Temp Conv No. Solvent (.degree. C.) Time (%) M.sub.n
M.sub.w/M.sub.n 1 Bulk.sup.a RT 10 min. 32 13700 2.8 2 50%
DMF.sup.a RT 31 hrs. 56 11000 3.5 3 10% DMF.sup.a 90 5 hrs. 57
12100 2.8 4 5% DMF.sup.b 70 13 hrs. 78 13880 1.2 5 10% ethylene 90
6.3 hrs. 71 8300 2.1 carbonate.sup.b 6 50% ethanol.sup.a 90 24 hrs.
41 6200 1.7 7 10% ethanol.sup.b 90 24 hrs. 66 14800 1.3 .sup.aratio
of [MA]:[MBrP]:[CuBr]:[CuBr.sub.2]:[DETA] = 230:1:0.5:0.5:1
.sup.bratio of [MA]:[MBrP]:[CuBr]:[CuBr.sub.2]:[DETA] =
230:1:1:0.1:1.1
[0337] The kinetics and molecular weight plots of the reaction
labeled above as Entry 4 showed linear first order kinetics and
good agreement of molecular weight with the predicted values.
EXAMPLE 18c
Polymerization of n-BA and MMA Using Cu/AEP
[0338] Initial experiments on polymerizations of n-BA and MMA in
bulk with Cu(I)Br, AEP, and initiator, showed no control of
molecular weights, broad molecular weight distributions, and
non-linear first order kinetics. The bulk polymerizations of these
monomers took place in heterogeneous reaction mixtures due to the
limited solubility of the Cu/AEP catalyst system in the monomers.
If the understanding of the requirements for preparation of a
suitable ligand were correct then the addition of solvent could
make this ligand useful in the same way that PMDETA and DETA were
made more effective. Several experiments were conducted using
different solvents and different amounts of solvent. The results of
these experiments are shown in Table 16. These reactions also show
that the addition of a polar solvent, in this case DMF or acetone,
can increase the level of control of the polymerization. These
reactions are very sensitive to the amount of solvent added, and
when the optimal amount of solvent was not used the reaction
displayed results similar to those seen for reactions in which no
solvent was added.
17TABLE 16 Results for ATRP of n-BA using MBrP/CuBr/AEP and MMA
using ethyl 2-bromoisobuytyrate (EBriB) T Conv No. M Solvent
(.degree. C.) Time (%) M.sub.n M.sub.w/M.sub.n 1 n-BA.sup.a bulk 80
40 min 67 14800 1.81 2 MMA.sup.b bulk.sup.b 70 3.5 hrs 79 20600
1.69 3 n-BA.sup.a 20% 80 3.3 hrs. 48 5000 1.75 DMF 4 n-BA.sup.a 10%
80 3 hrs. 90 10300 1.51 DMF 5 n-BA.sup.a 5% 80 4 hrs. 39 3750 2.06
DMF 6 MMA.sup.b 10% 80 3 hrs. 94 6700 1.47 DMF 7 n-BA.sup.a 10% 80
3 hrs. 99 15500 2.16 acetone 8 n-BA.sup.a 10% 50 3.6 hrs. 56 4500
1.9 acetone 9 n-BA.sup.a 10% RT 20 min 86 4000 2.6 acetone 10
n-BA.sup.a 50% 80 4 hrs. 90 11100 1.67 acetone .sup.aratio of
[n-BA]:[MBrP]:[CuBr]:[AEP] = 78:1:1:1 .sup.bratio of
[MMA]:[EBriB]:[CuBr]:[AEP] = 100:1:1:1 in 50% diphenyl ether
[0339] The kinetics and molecular weight plots of two
polymerizations of n-BA and MMA show good agreement between
measured molecular weight and molecular weight predicted by
DP=[M].sub.o/[I].sub.o, and low polydispersities.
[0340] Addition of redox conjugate to suspending media improves the
level of control in a biphasic controlled polymerization.
[0341] The advent of controlled/"living" radical polymerization
techniques, such as atom transfer radical polymerization (ATRP),
has improved the ease with which block copolymers can be
synthesized, and also expanded the range of monomers that can be
incorporated into the block copolymer. Furthermore, it has opened
the possibility of synthesizing block copolymers in water-borne
systems, where other mechanisms are too sensitive to water to
survive.
EXAMPLE 19
Emulsion Polymerizations with Substituted Bipyridines as
Ligands
[0342] A series of experiments were run under similar conditions
with different substituents present of the ligand to adjust the
solubility of the catalyst in the biphasic system. The results are
summarized below in Table 17.
18TABLE 17 Polymerization of BMA using bpy derivatives as the
ligand..sup.a T Ligand (.degree. C.) Time Conv. M.sub.n,th
M.sub.n,sec M.sub.w/M.sub.n 1 bpy 70 3.0 h 100% 28,400 272,000 3.27
2 dTbpy 70 2.1 h 98% 27,900 36,100 1.52 3 70.sup.b 1.8 h 93% 26,500
33,800 1.39 4 dNbpy 90 1.3 h 85% 24,200 32,300 1.28 5 dAbpy.sup.c
90 1.7 h 89% 25,300 37,200 1.33 6 70 1.8 h 88% 25,000 34,000 1.25 7
70.sup.d 2.0 h 90% 25,600 33,000 1.18 8 dHDbpy 90 2.2 h 83% 23,580
27,750 1.21 .sup.aBMA/water = 1.5 ml/10 ml, surfactant Brij 98,2%
vs. water, [EBiB].sub.0:[CuBr].sub.0:[ligand].sub.0 = 1:1:2
.sup.bwith 8% of CuBr.sub.2 (vs. Cu total) added .sup.cdAbpy:
mixture of dNbpy and (1) in 1/1 ratio .sup.dwith 11% of CuBr.sub.2
(vs. Cu total) added
[0343] The catalyst complexed with dHDbpy solubilizes well in the
system. Compared with the results using dNbpy or dAbpy as the
ligand under the same condition, the polymerization are slower,
both in direct ATRP and reverse ATRP. For direct ATRP of BMA, the
initiation efficiency and polydispersity are a little better when
using dHDbpy as the ligand, indicating more Cu(II) in the organic
phase. For reverse ATRP and the polymerization of BA, the
difference in molecular weight control between dHDbpy and dAbpy is
not obvious. From the point of view of both polymerization rate and
molecular weight control, dNbpy seems better than dHDbpy.
EXAMPLE 20
Emulsion Polymerization with a Terpyridene Ligand
[0344] Use of 4,4',4"-Tris(5-nonyl)-2,2':6',2"-terpyridine (tNtpy),
a substituted terpyridine also led to controlled polymerization of
BMA. With EBiB as the initiator at 70.degree. C., the monomer
conversion reached 84% after 1.7 h. The resultant polymer had
M.sub.n=37,200 and M.sub.w/M.sub.n=1.38. The fast rate of
polymerization, as well as the quick change in color of the
emulsified mixture from brown to blue, suggests that an even better
controlled polymerization may be attained at a lower
temperature.
EXAMPLE 21
Emulsion Polymerizations Using Aliphatic Amines as Ligands
[0345] The exemplary emulsion polymerization of butyl acrylate
using aliphatic amines as ligands are reported below in Table
18.
19TABLE 18 Polymerization of BMA using aliphatic amines as the
ligand..sup.a Ligand T(.degree. C.) Time Conv. M.sub.n,th
M.sub.n,sec M.sub.w/M.sub.n 1 PMDETA 70 3.0 h 100% 28,400 380,000
6.7 2 Me.sub.6TREN 70 3.0 h 100% 28,400 9,800,000 3.8 3
Me.sub.6TREN 20.sup.b 1.3 h 73% 20,800 928,700 2.2 .sup.aBMA/water
= 1.5 ml/10 ml, surfactant Brij 98, 5% vs. water,
[EBiB].sub.0:[CuBr].sub.0:[ligand].sub.0 = 1:1:1 .sup.bBrij 98, 3%
vs. water.
EXAMPLE 22
Use an ATRP Initiator in a "Reverse" ATRP Polymerization
[0346] Table 19 displays the results of an experiment wherein an
initiator for a normal forward ATRP polymerization is added to the
monomer in a "reverse" ATRP emulsion polymerization. The overall
control of the emulsion polymerization is improved.
20TABLE 19 Reverse ATRP in the presence of EBiB as added ATRP type
initiator. BMA/H.sub.2O = 1.5/10 ml, T = 90.degree. C., Brij 98 =
0.2 g EBiB/V-50/ Exp. DP.sub.th CuBr.sub.2/dNbpy Time Conv.
M.sub.n,th M.sub.n,sec* M.sub.w/M.sub.n* f BMA-162 100 1/0.5/1/2
4.7 h 92% 13080 23220 1.28 0.56 BMA-163 100 1/0.5/1.8/3.5 20 h 23%
/ / / / BMA-164 145 1/0.2/1/2 5.2 h 0% / / / / *Measured by
precipitation in methanol
[0347] Under appropriate conditions, the initiation efficiency was
improved from 0.2-0.3 for pure reverse ATRP to .about.0.6 in the
presence of EBiB. The particle size determined for the emulsion was
similar to that of the "reverse" ATRP polymerization.
EXAMPLE 23
Block Copolymers
[0348] Here we report conditions tailored for the synthesis of
block copolymers by ATRP in two distinct methods. Firstly,
water-borne block copolymers are synthesized, and secondly,
acrylate-methacrylate di- and tri-block copolymers are made in a
one-pot synthesis.
[0349] General Methods and Equipment.
[0350] Monomers (styrene (STY), n-butyl acrylate (B A), methyl
methacrylate (MMA), n-butyl methacrylate (BMA)) were run through a
column of alumina, distilled under vacuum and then stored at
-4.degree. C. under N.sub.2. Immediately before use they were
purged with N.sub.2 for at least 30 mins. CuBr was purified, and
the ligands (dAbpy, BPMODA) were synthesized, as reported earlier.
The ligands hexamethyltriethylenetetram- ine (HMTETA),
pentamethyldiethylenetriamine (PMDETA) were obtained from Aldrich
and used as received. Methyl 2-bromopropionate (MeBrP), ethyl
2-bromoisobutyrate (Et-2BriB) and hexadecane (HEX) were obtained
from Fisher and used as received. Monomer conversions were measured
by GC on either a Shimadzu GC14 or 17A, relative to an internal
standard. Molecular weights were measured on a GPC system
consisting of a Waters 515 pump, Waters 717plus Autoinjector, PSS
10.sup.5, 10.sup.3, 10.sup.2 ? columns and a Waters 410 RI
detector, and calibrated with either polystyrene or poly(methyl
methacrylate) standards. .sup.1H NMR spectra were collected on a
Bruker AM 300 MHz spectrometer in CDCl.sub.3.
EXAMPLE 23a
Water-Borne Block Copolymers: Pre-Synthesized Macroinitiator
[0351] A poly(n-butyl acrylate) (PBA) macro initiator was
synthesized by the ATRP of BA, CuBr, MeBrP and PMDETA in a mole
ratio of 100/1/0.2/0.2 at 60.degree. C. for 2 hours. After
dissolving in THF, the catalyst was removed by filtration through
alumina, and the excess monomer removed by evaporation. The number
average molecular weight (M.sub.n) was 9600 and polydispersity
(M.sub.w/M.sub.n) was 1.2. Between 0.5-1.0 g of PBA was transferred
into a round-bottom flask along with half of the required
surfactant (Brij98 or Tween20), and dissolved in approximately half
of the appropriate monomer (purged with N.sub.2 for at least 30
mins.). CuBr, ligand (either dApy or BPMODA), and surfactant was
added to a Schlenk flask and degassed with 3 vacuum/N.sub.2 cycles.
The other half of the monomer was then added to the Schlenk under
N.sub.2, and the catalyst/surfactant dissolved. Water (deionized,
purged with N.sub.2 for at least 30 mins.) was then added evenly to
both the PBA and catalyst solutions, and each stirred vigorously
for approximately 30-60 mins. The PBA solution was then cannulated
into the Schlenk flask. Samples were withdrawn at regular periods
by a N.sub.2-washed stainless steel syringe. It was noticed that if
the Schlenk (or a round-bottom flask) was sealed with a rubber
septum that it was often soaked in monomer by the end of the
reaction. Therefore, all reactions reported here were performed in
an all glass reactor.
[0352] An examination of the development of the molecular weight
distribution of a PBA-initiated water-borne ATRP of styrene with
the Brij98 surfactant shows a peak at .about.1500 from the
surfactant, and the macroinitiator peak shows a small, high
molecular weight peak. This later peak is most likely due to a
small amount of polymerization that occurs at the beginning of the
reaction before enough Cu.sup.II deactivator has been accumulated
to ensure good control. The polymer increases in molecular weight
and the molecular weight distribution remains narrow throughout the
polymerization. However, the polymerization mixture contained a
styrene phase at the meniscus that slowly disappeared during the
reaction, although the stability of the resulting `emulsion` was
also good.
EXAMPLE 23b
Acrylate/Methacrylate Block Copolymers: Sequential Addition of
Monomer
[0353] CuBr was weighed into a Schlenk flask equipped with a
magnetic stirring bar and degassed with 3 vacuum/N.sub.2 cycles.
n-BA (9 mL, purged with N.sub.2 for 30 mins) and PMDETA were added
and the solution placed in an oil bath and stirred to dissolve the
catalyst. The solutions were light green in color and homogeneous
to the eye. The initiator (either MeBrP or dimethyl
2,6-dibromoheptanedioate (DMDBHD)) was added to 1 mL of monomer
which was then stirred and cannulated into the monomer/catalyst
solution. After the desired time, a second MMA/CuCl/HMTETA solution
was made up. This was also homogeneous, and was cannulated into the
Schlenk flask. The solution quickly became less viscous, but then
progressively became more viscous within 30 mins. of this second
monomer addition. After a second time period of polymerization, THF
was introduced into the flask to dissolve the polymer. Samples had
the catalyst removed from them by filtration through alumina and
precipitated into methanol/water mixtures.
[0354] An examination of the molecular weight distributions from
two different experiments, one the synthesis of a diblock copolymer
of PBA-b-PMMA, and the other of a tri-block copolymer
PMMA-b-PBA-b-PMMA is informative. In each case, the PBA was grown
first (with monofimctional and difunctional initiators
respectively), then the MMA, with CuCl/HMTETA dissolved in it, was
added to the PBA. The molecular weight increased, and there is no
sign of terminated polymer that would correspond to `dead`
macroinitiator. The number average molecular weights,
polydispersities and monomer conversions are given in Table 20. In
each case the conversion of BA and then of MMA reached
approximately 90%, and the polydispersities remained low
(.about.1.20-1.25). These experiments show that ATRP can be applied
to the synthesis of block copolymers without the need to isolate
macroinitiators, even when there are several factors, such as
cross-propagation rates, that may effect the success of the block
copolymerization.
21TABLE 20 Kinetic and Molecular Weight Data. % Conversion Sample
Time (hrs) n-BA MMA M.sub.n M.sub.w/M.sub.n PBA-Br 2 91 0 9,700
1.25 PBA-b-PMMA 5 96 88 21,300 1.26 Br-PBA-Br 16.5 88 0 67,500 1.16
PMMA-b-PBA-b-PMMA 18.5 93 76 91,300 1.20
[0355] These experiments demonstrate that ATRP is a very versatile
method for synthesizing block copolymers, specifically being able
to produce block copolymers with free radically copolymerizable
monomers. This applies to both within water-borne polymerizations
and through sequential monomer additions in bulk
polymerizations.
EXAMPLE 24
Emulsion Polymerization Using Picolyl Amines as Ligands
[0356] Butyl acrylate was polymerized under standard conditions
using picolyl arnines as ligands. The results are presented in
Table 21.
22TABLE 21 Polymerization of BMA using picolyl amines as the
ligand..sup.a Ligand T(.degree. C.) Time Conv. M.sub.n,th
M.sub.n,sec M.sub.w/M.sub.n 1 BPMOA 70 2.5 h 94% 26,700 48,300 1.97
2 BPMODA 70 2.0 h 96% 27,300 43,100 1.78 .sup.aBMA/water = 1.5
ml/10 ml, surfactant Brij 98, 2% vs. water,
[EBiB].sub.0:[CuBr].sub.0:[ligand].sub.0 = 1:1:1
EXAMPLE 25
Use of a Less Active Monomer in Emulsion Polymerization Using
Picolyl Amines as Ligands
[0357] The two ligands were examined for the polymerization of a
less active monomer, butyl acrylate, the control was improved
because of the smaller equilibrium constants. The results are
presented in table 22.
23TABLE 22 Polymerization of BA using picolyl amines as the
ligand..sup.a Ligand T(.degree. C.) Time Conv. M.sub.n,th
M.sub.n,sec M.sub.w/M.sub.n 1 BPMOA 90.sup.b 3.0 h 81% 20,700
21,500 1.11 2 70 8.3 h 81% 20,700 31,900 1.64 BPMODA 90 3.0 h 93%
23,800 28,800 1.24 4 70 17 h 93% 23,800 27,100 1.20 a.Unless noted,
BA/water = 1.5 ml/10 ml, surfactant Brij 98, 2% vs. water,
[EBiB].sub.0:[CuBr].sub.0:[ligand].- sub.0 = 1:1:1 Bulk
polymerization. [EBiB].sub.0:[CuBr].sub.0:[liga- nd].sub.0 =
1:1:1
[0358] Potentially the partitioning constants of the Cu(II)
complexes may also play a role. BPMOA, although excellent in bulk
polymerization of butyl acrylate (entry 1), still resulted polymers
with polydispersities higher than 1.5 in water-borne system. This
indicated a poor solubility of the deactivator in the organic
phase. Having a longer hydrophobic chain, BPMODA greatly enhances
the organic solubility of Cu(II) species. As a consequence, the
polymerization of butyl acrylate using BPMODA as the ligand was
well controlled, as evidenced by a linear increase of molecular
weight with monomer conversion, as well as polydispersities less
than 1.3 throughout the polymerization.
EXAMPLE 26
ATRP of Styrene, MA and MMA Catalyzed by Cu(I) Complexed by
Pyridine-Imine Ligands.
[0359] The results of the extension of pyridine-imine ligands to
the ATRP polymerization of styrene and methyl acrylate are reported
below in table 23, and compared to the results on the
polymerization of methyl methacrylate.
24TABLE 23 ATRP of Styrene, MA and MMA Catalyzed by Cu(I) Complexed
by OPMI or PMOI Temp Time Conv Ligand Monomer (.degree. C.) (h) (%)
M.sub.n, Cal M.sub.n, SEC M.sub.w/M.sub.n OPMI styrene.sup.a 110
15.0 92 9200 10400 1.34 OPMI MA.sup.b 90 15.0 84 16800 14700 1.23
OPMI MMA.sup.c 90 3.50 53 10600 15800 1.33 PMOI styrene.sup.a 90
1.05 75 7500 11500 1.33 PMOI MA.sup.b 110 0.50 58 11600 12100 2.03
PMOI MMA.sup.d 90 0.50 62 12400 15100 1.50 .sup.abulk;
[styrene].sub.o/[ligand].sub.o = 96;
[PEBr].sub.o/[CuBr].sub.o/[ligand].s- ub.o = 1/1/2. .sup.bbulk;
[MA].sub.o/[EBP].sub.o = 232;
[EBP].sub.o/[CuBr].sub.o/[ligand].sub.o = 1/1/2. .sup.c50 vol % in
anisole; [MMA].sub.o/[EBiB].sub.o = 200;
[EBiB].sub.o/[CuCl].sub.o/[li- gand].sub.o = 1/1/2. .sup.d50 vol %
in anisole; [MMA].sub.o/[EBiB].sub.o = 200;
[EBiB].sub.o/[CuBr].sub.o/[ligand].sub.o = 1/1/2.
EXAMPLE 27
Polymerization Using Tridentate Pyridine-Imine Based Ligands
[0360] Two tridentate ligands containing the pyridine-imine moiety,
N-(2-pyridylmethyl)-(2-pyridyl)methanimine (PMPMI) and
N-(2-N-(dimethyl)ethyl)-(2-pyridyl)methanimine (DMEPMI), were
synthesized by the condensation reactions using bidentate primary
amines with 2-pyridinecarboxaldehyde. Complexes of copper(I) and
tridentate nitrogen ligands generally show a different conformation
(e.g., squarer pyramidal) than the tetrahedral conformation found
in most complexes of copper(I) and bidentate nitrogen ligands. As a
result, a ligand to metal ratio of 1 is sufficient to achieve the
maximum rate of polymerization. Table 24, displays the results of
the ATRP using the two tridentate ligands. With PMPMI as the
ligand, well-controlled polymerizations were obtained for both
styrene and MA; however, high polydispersity was observed for MMA.
When DMEPMI was used as the ligand, well-controlled polymerization
was again obtained for styrene, with a slight increase of
polydispersity for MA and a decrease of polydispersity for MMA.
25TABLE 24 ATRP of Styrene, MA and MMA Catalyzed by Cu(I) Complexed
by PMPMI or DMEPMI Ligand Monomer Temp (.degree. C.) Time (h) Conv
(%) M.sub.n, Cal M.sub.n, SEC M.sub.w/M.sub.n PMPMI styrene.sup.a
110 1.5 60 6000 8100 1.14 PMPMI MA.sup.b 0 2.0 57 11400 12300 1.06
PMPMI MMA.sup.c 90 1.5 40 8000 17700 2.77 DMEPMI styrene.sup.a 90
3.2 61 6100 7200 1.17 DMEPMI MA.sup.b 110 5.2 47 9500 15000 1.37
DMEPMI MMA.sup.c 90 1.0 29 5800 10500 1.67 .sup.abulk;
[styrene].sub.o/[PEBr].sub.- o = 96;
[PEBr].sub.o/[CuBr].sub.o/[ligand].sub.o = 1/1/1. .sup.bbulk;
[MA].sub.o/[EBP].sub.o = 232; [EBP].sub.o/[CuBr].sub.o/[ligan-
d].sub.o = 1/1/1. .sup.c50 vol % in anisole;
[MMA].sub.o/[EBiB].sub.o = 200;
[EBiB].sub.o/[CuCl].sub.o/[ligand].sub.o = 1/1/1.
[0361] The kinetic plots for the polymerization of styrene and MA
using PMPMI as the ligand were drafted and linear plots of
ln([M].sub.o/[M].sub.t) vs time was observed for both monomers
indicating the constant concentration of the growing radicals.
Molecular weights showed a linear increase along with conversion,
and the measured molecular weights were close to the calculated
values for MA. The polydispersities of the resulting polymers
remained quite low throughout the polymerization
(M.sub.w/M.sub.n.about.1.1-1.2), indicative of a fast exchange
between the active sites and the dormant species.
EXAMPLE 28
Controlled Polymerizations Using Supported Ligands
[0362] The initial series of experiments were conducted using
"standard" ATRP polymerization conditions. The results are reported
in Table 19 for polymer supported s-TERN as ligand
26TABLE 25 Results of Polymerization Using Polymer-Supported Tris(2
aminoethyl)amine (s-TREN) with Ethyl 2-Bromopropionate as
Initiator. [M].sub.o/[I].sub.o/ [CuBr].sub.o/ Te Time Conv. M.sub.n
M.sub.n, th M [L].sub.o [.degree. C.] [min] [%] [10.sup.3]
[10.sup.3] M.sub.w/M.sub.n MA 200/1/1/1 90 90 60 11.7 10.5 3.14 a
MA 200/1/1/1 90 220 76 7.48 13.8 3.28 a St 100/1/1/1 110 220 55
5.95 5.49 12.2 a MMA.sup.b 200/1/1/1 90 120 29 3.82 5.76 19.6 c a
[M].sub.o/[I].sub.o/[CuBr].sub.o/[L].sub.o = [monomer].sub.o/methyl
2-bromopropionate].sub.o/[CuBr].sub.o/[s-TREN].sub- .o .sup.b50
vol.-% anisole solution c
[M].sub.o/[M].sub.o/[CuBr].sub.o/[L].sub.o =
[MMA].sub.o/[2-bromopropioni-
trile].sub.o/[CuBr].sub.o/[s-TREN].sub.o
EXAMPLE 28a
Tailored Polymer Supported Ligands
[0363] N,N-Bis(2-pyridylmethyl)-2-hydroxyethylamine (HO-BPMEA) was
immobilized on commercially available Merrifield resin containing
benzyl chloride functional group, which is used widely for peptide
synthesis and combinatorial synthesis of small organic molecules
Methyl acrylate (MA) was chosen for study since HO-BPMEA provided
one of the best-controlled solution polymerizations of MA. In the
first experiment, a bimodal molecular weight distribution was
observed by SEC. The reason for the bimodal molecular weight
distribution was not immediately clear, but it is likely that the
initial growing radicals cannot easily access the deactivator and
thus polymerize in uncontrolled manner with normal free radical
termination reactions occurring (high molecular peak). After
generation of enough amounts of deactivator by termination, a fully
controlled polymerization then proceeds (low molecular peak).
EXAMPLE 28b
Addition of Redox Conjugate
[0364] Varying levels of CuBr.sub.2 were added to the
polymerization and the results are presented in Table 26.
27TABLE 26 Results of polymerization using supported s-BPMEA ligand
carried out under different conditions [M].sub.o/[I].sub.o/
[CuBr].sub.o/ Temp M.sub.n(th.) No. M [CuBr.sub.2].sub.o/[L].sub.o
[.degree. C.] Time [min] Conv. [%] M.sub.n[10.sup.3] [10.sup.3]
M.sub.w/M.sub.n 1 MA 230/1/1/0/1.sup.c 22 180 32 10.2 6.4
57.4.sup.d 2.sup.a MA 230/1/0.75/0.25/1.sup.c 90 60 50 40.8 10.6
2.68 3.sup.a MA 230/1/0.50/0.50/1.sup.c 90 180 62 36.7 12.5 1.90
4.sup.b MA 230/1/0.25/0.75/1.sup.c 90 930 67 26.7 13.4 1.62 6.sup.a
MMA.sup.e 203/l/0.50/0.50/1.sup.f 90 900 68 23.9 13.7 1.92 7.sup.a
St 192/1/0.50/0.50/1.sup.c 90 900 66 30.0 13.1 2.14 .sup.aReaction
was stirred at 22.degree. C. for 3 hours before heating
.sup.bReaction was stirred at 22.degree. C. for 40 min before
heating .sup.c[M].sub.o/[I].sub.o/[CuBr].sub.o/[CuBr.sub.2].sub.o-
/[L].sub.o =
[monomer].sub.o/[2-bromopropionate].sub.o/[CuBr].sub.o/[CuBr.-
sub.2].sub.o/[s-BPMEA].sub.o .sup.dBimodal distribution .sup.e50
vol.-% anisole solution .sup.f[M].sub.o/[I].sub.o/[CuBr]-
.sub.o/[CuBr2].sub.o/[L].sub.o/ =
[monomer].sub.o/[2-bromopropionitrile].s-
ub.o/[CuBr].sub.o/[CuBr.sub.2].sub.o/[s- BPMEA].sub.o
[0365] The following examples are provided only to illustrate the
present invention and are not meant to be limiting.
EXAMPLE 29
Synthesis and Functionalization of poly(methyl acrylate) (pMA) Star
with 1.2-epoxy,5-hexene
[0366] The synthesis of a star polymer with epoxy groups at the
terminus of each arm was conducted by the ATRP of MA from a
trifluctional initiator, followed by ATRA of the polymer to a
fluctional alkene. Poly(methyl acrylate) stars prepared from ATRP
were purified by passing the polymer solution through alumina
before use in ATRA reactions. The synthesis of the pMA star was
performed by using a Cu(I)Br/PMDETA catalyst, and
1,1,1-tris(2-bromoisobutyryloxy)phenyl ethane as the initiator. The
polymerization was stopped at 70% monomer conversion to insure
retention of alkyl halide chain end functionality. Molar masses of
the star polymers was determined by SEC, using linear PS standards
(M.sub.n=7,390; M.sub.w/M.sub.n=1.08). Functionalization of pMA
stars by ATRA reactions was done using a Cu(I)Br/dTbpy catalyst.
The flnctionalization reaction was monitored by .sup.1H NMR
analysis, where the disappearance of end-group methine protons (m,
1H, .delta.=4.2 ppm) and the formation of glycidyl protons (s, 3H,
.delta.=2.9, 2.7, 2.5) suggested efficient formation of
epoxy-functionalized star polymers.
Example 30
Synthesis and Functionalization of Hyperbranched Polymers
[0367] Hyperbranched polymers were prepared by the ATRP of
2-(2-bromopropionyloxy)ethyl acrylate (BPEA), using a Cu(I)Br/dTbpy
catalyst. Using both SEC and .sup.1H NMR analysis, the polymer was
estimated to be highly branched, possessing a high degree of alkyl
halide functionality. Residual catalyst was then removed from the
polymer by dissolution of the polymer in THF, followed by
filtration through alumina. ATRA of 1,2-epoxy,5-hexene was then
conducted with purified pBPEA, using additional Cu(I)Br/dTbpy as
the catalyst. From this reaction, hyperbranched pBPEA with epoxy
groups at the periphery of the polymer was obtained. The ATRA
functionalization reaction was monitored by .sup.1H NMR, where the
disappearance of methyl protons adjacent to a bromine (d, 3H,
.delta.=1.8 ppm) was observed, along with the formation of glycidyl
proton resonances (s, 3H, .delta.=2.9, 2.7, 2.5). From the .sup.1H
NMR analysis, high conversions (p.ltoreq.0.90) of alkyl halide
end-groups to epoxy groups were observed. Other resonances observed
at .delta.=1.4-2.2 were assigned to aliphatic protons from the
alkene formed after radical addition to the polymer.
[0368] The "arm first" technique involved the preparation of
macroinitiators with living chain ends, followed by microgel
formation using multifunctional linkers or divinyl reagents.
Poly(t-butyl acrylate) (PtBA) star polymers were prepared by this
technique. First, well-defined PtBA was prepared using methyl
2-bromopropionate as the initiator and CuBr/PMDETA as the catalyst
in 25% acetone at 60.degree. C. The isolated PtBA (M.sub.n=6,900,
M.sub.w/M.sub.n=1.18) along with divinyl reagents, such as
divinylbenzene (DVB), were reacted to form multiarmed stars, by
ATRP. This technique was extended towards the preparation of
functional star polymers, with functionality at the terminus of
each arm. A variety of functional initiators can be used in ATRP
due to the wide tolerance of functional groups inherent to radical
processes. For example, PtBA with epoxy .alpha.-end functional
groups was synthesized using 1,2-epoxypropyl 2-bromopropionate as
the initiator. The molar mass of the macroinitiator was determined
by SEC (M.sub.n=5,600, M.sub.w/M.sub.n=1.30). The molar mass was
also determined from .sup.1H NMR by integrating the resonances of
side chain over the resonances from terminal functional groups at
the end of each arm. The molecular weights estimated by .sup.1H NMR
(M.sub.n=6,300) agreed with values measured by SEC. This suggested
that the functionalities were retained during the polymerization.
The ATRP of the epoxy functional PtBA macroinitiator with DVB
afforded functional star polymers with epoxy groups at the end of
each arm. For these reactions, the efficiency of the star synthesis
by ATRP was not affected by the presence of functional groups from
the initiator.
EXAMPLE 31
Formation of Functional Poly(t-butyl Acrylate) Star Polymers
[0369] t-Butyl acrylate (tBA) was washed with 5% NaOH aqueous
solution to remove the acid and then washed with H.sub.2O until the
aqueous phase was neutral. The solution was dried over CaCl.sub.2,
filtered, and then distilled under reduced pressure. The monomer
was stored at -20.degree. C. under argon prior to use. CuBr was
purified according to the published procedure set forth U.S. Pat.
No. 5,763,548. Other reagents were all commercial products and used
without further purification.
EXAMPLE 31a
Kinetic Studies of the ATRP of tBA
[0370] A dry round-bottom flask was charged with CuBr (19.6 mg,
0.137 mmol), N,N,N',N",N"-pentamethyldiethylenetriamine (PMDETA)
(28.5 .mu.L, 0.137 mmol), tBA (2 ml, 13.7 mmol), anisole (0.5 mL),
and a magnetic stir bar. The flask was sealed with a rubber septum,
and degassed by three freeze-pump-thaw cycles. The flask was then
immersed in an oil bath with the thermostat set at 60.degree. C.,
and methyl 2-bromopropionate (MBP) (30.4 mL, 0.272 mmol) was added
slowly. At timed intervals, aliquots of the reaction solution were
withdrawn via syringes fitted with stainless steel needles, and
were dissolved in THF to measure conversion (GC) and molecular
weight (SEC).
[0371] Synthesis of tBA Macroinitiators. PtBA macroinitiators were
prepared in 25 vol % p-dimethoxybenzene (DMB) solution at
60.degree. C. using the above mentioned procedure. The reaction
mixture were dissolved in acetone after the polymerization, and
were precipitated in 50 vol % methanol/H.sub.2O after passing
through an alumina column to remove the copper complexes. The
samples were redissolved in ethyl ether and then concentrated using
a rotary evaporator, followed by drying under vacuum at room
temperature for 2 days
EXAMPLE 31b
Synthesis of Star Polymers Using Macroinitiators
[0372] In a typical experiment, a dry glass tube was charged with
CuBr (4.2 mg, 29.3 .mu.mol), PMDETA (6.1 .mu.L, 29.2 [mol), PtBA
macroinitiator (0.2 g, 29.0 .mu.mol), DVB (62.0 .mu.L, 0.435 mmol),
anisole (0.5 mL) and a magnetic stir bar. The glass tube was
degassed by three freeze-pump-thaw cycles and sealed under vacuum.
The glass tube was immersed in an oil bath with the thermostat set
at 110.degree. C. After 5 h, the glass tube was taken out and
broken. The sample was dissolved in THF to measure conversion (GC)
and molecular weight (SEC).
[0373] Characterization. Monomer conversions were determined from
the concentration of the residual monomer on a Shimadzu GC-14 gas
chromatograph equipped with a J&W Scientific 30 m DB-WAX column
and a flame ionization detector with helium as the carrier gas.
Molecular weights and molecular weight distributions were measured
on PSS SDV columns (Guard, 10.sup.5, 10.sup.3, and 10.sup.2)
coupled with a Waters 410 differential refractometer using THF as
the eluent. PSS GPC scientific software version 4.02 was used to
analyze the data. .sup.1H NMR was performed on a Brucker WP300
instrument using CDCl.sub.3 as the solvent.
[0374] ATRP of tBA. tBA was polymerized according to procedures
disclosed in earlier applications using CuBr complexed by
N,N,N',N",N"-pentamethyld- iethylenetriamine (PMDETA) as the
catalyst and methyl 2-bromopropionate (MBP) as the initiator. Under
typical reaction conditions, a linear semilogarithm plot of monomer
conversion vs time was observed indicating a constant number of
propagating chains. The molecular weights (M.sub.n) of PtBA
increased linearly with the conversion and agreed well with the
predicted values assuming that each initiator molecular produced
one polymer chain. SEC traces of the obtained polymers displayed
narrow monomodal molecular weight distribution (M.sub.w/M.sub.n)
which decreased with the monomer conversion. These observations
suggested that the polymerization was a controlled process. The Br
.omega.-functionality of thus prepared PtBA as isolated
macroinitiators was assessed by chain extension using a fresh batch
of tBA monomer or cross propagation to styrene (St) to form block
copolymers. Examination of the overlaid SEC traces of the PtBA
macroinitiator, the resulting PtBA-b-PtBA polymer after chain
extension to a new batch of tBA, and the PtBA-b-PSt block copolymer
displayed a clean shift of the SEC traces towards higher molecular
weights indicated that most of the PtBA macroinitiator chain ends
had reactive Br functional groups.
[0375] Effect of the coupling reagent. Three commercially available
divinyl coupling reagents, divinylbenzene (DVB), 1,4-butanediol
diacrylate (BDDA), and ethylene glycol dimethacrylate (EGDMA), were
reacted with the PtBA macroinitiator (M.sub.n,SEC=6900,
M.sub.w/M.sub.n=1.18) using CuBr/PMDETA as the catalyst in anisole
at 110.degree. C. DVB, BDDA and EGDMA were chosen as the coupling
reagents due to their structural resemblance to styrene, acrylate
and methacrylate, the three common monomers used in ATRP. Under the
reaction conditions, EGDMA led to a complete gelation of reaction
mixture within 1.5 h while BDDA and DVB led to no significant
gelation after 20 h. When BDDA was used as the coupling reagent,
the reaction medium turned viscous quickly but remained fluid. The
SEC trace showed that BDDA led to significant star-star coupling
and afforded star polymers with high molecular weights and broad
molecular weight distributions. In contrast, DVB led to the
formation of star polymers with narrow molecular weight
distributions. Approximately 5% of high order star polymer was
formed after 20 h as estimated using the SEC analysis software.
These results were consistent with the previous studies on the PSt
star polymer formation under similar conditions.
[0376] Effect of DVB to macroinitiator ratio. The formation of star
PtBA using DVB as the coupling reagent was studied in more detail
with varying ratios of DVB to PtBA macroinitiator. The molecular
weights of star polymers increased with an increasing ratio of DVB
to PtBA. The ratio of DVB/PtBA of 15 was found to be optimal,
leading to a high yield (i.e., high conversion of the
macroinitiator) of star polymer without significantly broadening
the molecular weight distribution. The yield of star polymer was
estimated from the ratio of SEC peak integration of the star
polymer and the macroinitiator using the function provided by the
SEC analysis software. Lower ratios of DVB to PtBA afforded star
polymers with lower yields. For example, DVB/PtBA ratios of 5 or 10
resulted in yields of 82% and 86%, respectively. A higher DVB/PtBA
ratio of 20 led to a significantly broader molecular weight
distributions of star polymers without significant improvement of
the yield.
[0377] The molecular weights of the star polymer were estimated
form polystyrene-calibrated SEC with an RI detector. These were
apparent molecular weights since the hydrodynamic volumes of PtBA
star polymers were obviously different from that of linear
polystyrene. The absolute molecular weights determined by triple
detection SEC were significant different from the RI detection SEC.
For example, for the PtBA star polymer prepared with a DVB to PtBA
ratio of 15, measurement by single detection SEC afforded
M.sub.n=53600 and M.sub.w/M.sub.n=1.71.
[0378] Effect of CuBr.sub.2 and exchange halogen. Other factors
pertinent to the polymerization were adjusted in an attempt to
further improve the yield of star polymer formation. Additional
CuBr.sub.2 (20% of total Cu) was added in the hope that radical
coupling reaction would be further suppressed in the presence of
excess Cu(II) deactivator. However, SEC analysis of the resulting
polymer showed that the yield was not improved. The use of
CuCl/PMDETA as the catalyst was studied. It was reported previously
that halide exchange reaction using macroinitiators with Br end
groups in the presence CuCl/ligand led to an improved
macroinitiator initiation in comparison with the propagation of the
second monomer during the block copolymer formation. This would
favor the cross propagation to form the short DVB block, and
disfavor the addition of polymeric radical terminal to DVB block on
another polymer chain (cross link to form microgel star core) since
C--Br bonds were broken during the cross propagation and mainly
C--Cl bonds were cleaved during the cross linking. Indeed, when
CuCl was used in place of CuBr, PtBA star polymers with similar
molecular weights and molecular weight distributions were obtained.
The yield of the star formation was fturther improved to 95% in
comparison with 90% in the case of CuBr.
[0379] Effect ofreaction time. Using a ratio of
DVB/PtBA/CuCl/PMDETA=15/1/- 1/1, the kinetics of star formation was
studied. The conversion of DVB was measured by GC. Reaction time of
5 h seemed to be optimal for the star formation. Longer reaction
time led to star-star coupling which was evident from the presence
of high molecular weight shoulder in the SEC traces for the
reaction time of 7.5 h and 20 h. The semilogarithm plot of DVB
conversion vs. time displayed first order kinetics with respect to
DVB until the reaction time of 5 h, and then the conversion leveled
off which was consistent with the SEC data. This suggested that
during the first 5 h of the reaction there were active
macroinitiator chain ends and sterically accessible star cores in
the reaction solution that continued to add to the DVB molecules in
solution and to the dangling vinyl groups on the DVB block on other
polymer chains. After 5 h, uncross-linked macroinitiator chains
were nearly depleted, and the star core became sterically
congested. As a result, the consumption of DVB and the addition of
polymeric radical to star core progressively slowed down. The star
formation process was also followed by .sup.1H NMR. The methoxy
protons (H.sub.a) and the proton (H.sub.b) adjacent to Br group on
the last tBA unit were clearly visible. During the star formation,
the signal from H.sub.b decreased with the reaction time and
eventually disappeared indicating that all the macroinitiator chain
extended to form block copolymers with DVB. The dangling vinyl
protons (H.sub.c) and phenyl protons (H.sub.d) on the DVB units
showed an initial increase in intensities but decreased with the
reaction time, and had significantly lower intensities than those
estimated from DVB conversion. These results were consistent with
the formation of a star-shaped polymer with mobile PtBA arms and a
DVB microgel core. The star core formed initially were loose and
had some degree of intramolecular mobility. The star core hardened
as cross linking progressed. The loss of intramolecular mobility
eventually caused the .sup.1H NMR signals of the microgel core to
be too broad to be detected.
[0380] Effect of solvent. Reactions were carried out in various
solvents to study the effect of the solvent on the star formation
process. After the same amount of reaction time (5 h), star
polymers formed in benzene showed significantly higher molecular
weight and broader molecular weight distribution than those carried
out in polar solvents. This result was further supported by
relatively high conversion of DVB compared to other systems and
high degree of cross linking indicated by the formation of some
insoluble star polymers (gels). These observations were attributed
to the relatively poor solubility of Cu(II) complex in benzene. The
low concentration of Cu(II) complex led to higher concentration of
radicals and higher degree of radical determination reactions.
Polar solvents, such as 1,2-dichlorobenzene and ethyl acetate,
provided star polymers with similar molecular weights distributions
and DVB conversions as in the case of anisole. 2-Butone as a
solvent afforded star polymers with slightly lower molecular weight
and DVB conversion, probably due to the good solubility of Cu(II)
complexes and/or relatively low solubility of polystyrene units in
this solvent.
EXAMPLE 31c
End Functional PtBA Stars
[0381] A variety of functional initiators were used directly during
the macroinitiator synthesis due to the tolerance of ATRP process
to different functional groups. For example, 1,2-epoxypropyl
2-bromopropionate was used to prepare PtBA macroinitiator with an
epoxy .alpha.-functional and a bromine co-functional end. The
isolated macroinitiator has M.sub.n,SEC=5,600 and
M.sub.w/M.sub.w=1.22 by SEC. Alternatively, the molecular weight
was determined using .sup.1H NMR by comparing the integration of
the protons on the side chains with that of protons adjacent to the
.alpha.- or .omega.-functional group. The consistence of molecular
weight obtained by NMR (M.sub.n,NMR=6,300) with that by SEC
suggested high functionality of the PtBA macroinitiator on both
polymer chain ends. When this functional macroinitiator was reacted
with DVB, end functional star polymers with epoxy end functional
groups were obtained. The yield of the star polymer using the epoxy
functional macroinitiator was similar to that of non-functional
PtBA which suggested that star formation under ATRP conditions was
not effected by the presence of functional groups. .sup.1H NMR
spectrum of epoxy functional star polymer showed the presence of
the epoxy group as well as the disappearance of signals from the
proton adjacent to Br group on the last tBA unit (Hf). Again,
signals from DVB microgel core and the dangling vinyl bonds had
lower intensities than the value estimated from DVB conversion as
discussed previously. These data were consistent with the proposed
star formation mechanism. Similarly, end functional stars with
hydroxy-, amino-, cyano-, and bromine end functional groups on the
out layers were prepared in good yields. The conservation of the
functional groups were all confirmed by .sup.1H NMR
[0382] These experiments in this example exemplify a method to form
functional star copolymers through use of telechelic PtBA as
macrotelefunctional feedstock. PtBA star polymers have been
successfully prepared by the "arm first" method using
copper-mediated ATRP. Among different divinyl coupling reagents
used, DVB provided PtBA star polymers with highest yield and
narrowest molecular weight distribution. Several factors pertinent
to the star formation, including the choice of the exchange
halogen, the addition of Cu(II) deactivator species, the ratio of
DVB to macromer, and the star formation time were addressed. End
functional stars have been successful synthesized by introducing
.alpha.-functional groups directly onto the PtBA macroinitiators.
Star polymers with various end functional groups, such as hydroxy-,
epoxy-, amino-, cyano-, and bromine groups, were prepared. The
above example discussed homopolymeric arms but the properties of
the "star" could be further modified, or controlled, by first
preparation of block, random or gradient copolymers prior to
coupling.
EXAMPLE 32
Synthesis of the poly(methyl acrylate) Three-Armed Star and
Hyperbranched Polymer and Radical Addition to 1
2-epoxy,5-hexene
[0383] Poly(methyl acrylate) star polymer and hyperbranched
poly(2-2-(bromopropionyloxy)ethyl acrylate), (pBPEA, M.sub.n=2950,
M.sub.w/M.sub.n=4.8, against linear PS standards), were synthesized
as reported in earlier publications.
EXAMPLE 32a
Radical Addition to 1 2-epoxy-5-hexene
[0384] To a degassed mixture of 4,4'-di-tert-butyl-2,2'-bipyridyl
(dTbpy), star or hyperbranched polymer, and CuBr, degassed
1,2-epoxy-5-hexene was added. The reaction was stirred at
70.degree. C. The polymer was recovered by precipitation into
n-hexanes (10-fold excess).
EXAMPLE 33
Poly(t-butyl acrylate) Stars
[0385] The poly(t-butyl acrylate) (PtBA) macroinitiators were
prepared via a procedure described previously. To prepare PtBA
stars, a dry glass tube was charged with CuBr,
N,N,N',N",N"-pentamethyldiethylenetriamine (PMDETA), PtBA macro
initiator, divinylbenzene (DVB), anisole and a magnetic stir bar.
The glass tube was degassed by three freeze-pump-thaw cycles and
sealed under vacuum. The glass tube was immersed in an oil bath
with the thermostat set at 110.degree. C. After a certain time, the
glass tube was taken out and broken. The sample was dissolved in
THF to measure conversion (GC) and molecular weight.
EXAMPLE 34
Functional DIOLS
[0386] Materials: Methyl acrylate was distilled over calcium
hydride at reduced pressure. The middle fraction was collected and
stored under nitrogen at -18.degree. C. Nitrogen was dried by
passing it through DRIERITE.RTM.. Cuprous bromide was purified by
stirring it in acetic acid for five days and drying it at 1 mm Hg,
100.degree. C. for three days.
N,N,N',N",N"-pentamethyldiethylenetriamine (PMDETA) was purified by
fractional distillation at 78.degree. C., 2 mm Hg. All other
reagents were used as received.
[0387] Measurements: GC and GPC measurements were made according to
published procedures..sup.i Polymer composition was measured by
.sup.1H NMR using a 300 MHz Bruker spectrometer operated by Tecmag
data acquisition software. MALDI-TOF MS-spectra (in linear mode)
were obtained using a PerSeptive Biosystems' Voyager Elite
instrument, equipped with a N.sub.2 laser at 337 nm. Dithranol, 0.1
M in THF, doped with Na.sup.+, was used as the matrix solution.
Electrospray Ionization (ESI) MS was conducted using a Finnegan
LCQ, equipped with an octupole and an ion trap mass analyzer.
Polymer solutions (10.sup.-4 M in methanol, doped with Na.sup.+)
were injected at 3 .mu.l/min.
[0388] Polymerizations: Appropriate amounts of p-dimethoxybenzene
and cuprous bromide were placed in a Schlenk flask, which was
sealed with a rubber septum and purged with nitrogen for 15 min.
Methyl acrylate was purged with nitrogen for 15 min, and ca. 5 mL
was added to the reaction flask by syringe. PMDETA was added. The
reaction flask was subjected to three freeze/pump/thaw cycles. The
initiator was added. The reaction mixture was heated to 60.degree.
C. Samples were collected by syringe. The ratio of I:CuBr:PMDETA
was 20:1:1 for the initiator (I) being dimethyl
2,6-dibromoheptadionate and 10:1:1 for the initiator being ethylene
glycol mono(2-bromoisobutyrate).
[0389] Functionalization: Poly(methyl acrylate)-diols were prepared
in situ by polymerizing methyl acrylate. At ca. 80% conversion, 15
equivalence of allyl alcohol to the chain ends, copper(0), cuprous
bromide, and PMDETA were added, the ratio of I:CuBr:Cu(0):PMDETA
was 1:1:3.8:1. The reaction was allowed to stir. Samples were
removed for ESI-MS and .sup.1H NMR analysis.
[0390] Coupling ofpoly(methyl acrylate). Poly(methyl acrylate) and
cuprous bromide were added to a round-bottomed flask. The flask was
sealed and purged with nitrogen for 15 min. Benzene, PMDETA, and a
coupling agent such as m-diisopropenylbenzene or
.alpha.-methylstyrene were added. The ratio of chains to coupling
agent was varied from 2 to 4. The ratio of chains:PMDETA:CuBr was
1:1:1.
EXAMPLE 35
Extension of "Reverse" ATRP Initiators to Include Peroxides
[0391] The use of conventional radical initiators in ATRP in the
presence of complexes of transition metals in their higher
oxidation state, has been reported and referred to as "reverse" or
"alternative" ATRP. The range of "standard free radical initiators"
that can be used in such "reverse" ATRP reactions can now be
expanded to include peroxides. This expansion is demonstrated by
the results of the homogeneous "reverse" copper-mediated ATRP using
as the initiator benzoyl peroxide (BPO) which are presented, and
compared with those using azobisisobutyronitrile (AIBN).
[0392] Table 26, compares the results of the bulk styrene
polymerization initiated by AIBN and BPO in the presence of
CuBr.sub.2 or CuBr complexed by 4,4'-di(5-nonyl)-2,2'-bipyridine
(dNbpy). Earlier work has shown that the addition of CuBr to AIBN
initiated systems has little effect on kinetics, molecular weights
(M.sub.n) or polydispersities (M.sub.w/M.sub.n). However, AIBN in
the presence of CuBr.sub.2/2dNbpy leads to a successful "reverse"
ATRP. In contrast, uncontrolled and slow polymerization was
obtained when BPO was used in conjunction with CuBr.sub.2/2dNbpy
under similar conditions. Surprisingly, control of the
polymerization for BPO initiated system was obtained in the
presence of CuBr/2dNbpy. When the reaction was carried out in the
presence of salts whose anions can not reversibly deactivate the
growing radicals, an uncontrolled polymerization, similar to BPO
alone, was obtained.
28TABLE 26 Polymerizations of Styrene in Bulk at 110.degree. C.
Initiated by AIBN and BPO in the Presence of Copper Complexes
[In].sub.o/ [M.sub.tX].sub.o/ Time conv M.sub.n, entry M.sub.tX In
[dNbpy].sub.o (h) (%) SEC M.sub.w/M.sub.n 1.sup.a AIBN 1/0/0 1.0 66
9700 2.60 2.sup.a CuBr AIBN 1/1/2 1.0 64 9200 2.90 3.sup.b
CuBr.sub.2 AIBN 0.6/1/2 4.6 69 5500 1.11 4.sup.c BPO 1/0/0 0.5 86
11300 2.19 5.sup.d CuBr.sub.2 BPO 0.6/1/2 39.0 19 oligomer 6.sup.c
CuBr BPO 1/1/2 1.5 61 10700 1.14 7.sup.c CuAc BPO 1/1/2 0.5 51
18800 1.92 8.sup.c CuAc.sub.2 BPO 1/1/2 0.5 82 11900 2.21
.sup.aConditions: Initiator (In) = AIBN; [styrene].sub.o = 8.6 M;
[styrene].sub.o/[AIBN].sub.o = 96. .sup.b[styrene].sub.o/[AIBN].s-
ub.o = 160. .sup.c[styrene].sub.o/[BPO].sub.o = 96.
.sup.d[styrene].sub.o/[BPO].sub.o = 160.
[0393] The differences in the initiation process for AIBN and BPO
have been discussed earlier and these discussions were based on an
examination of the results of the kinetic studies of the
polymerization of styrene using the AIBN/CuBr.sub.2 and the
BPO/CuBr initiating system, respectively show in both cases, that
the rate of polymerization increases with an increase of either
AIBN or BPO concentration, as a result of more radicals being
generated by the decomposition of the initiator. The molecular
weight values increased linearly with conversion. For AIBN, the
apparent initiator efficiency (apparent initiator
efficiency=M.sub.n,Cal/M.sub.n,SEC) slightly decreased with a
increase of the [AIBN].sub.o/[CuBr.sub.2/2dNbpy].sub.o ratio,
possibly due to termination reactions caused by the insufficient
deactivation by CuBr.sub.2 at the beginning of the polymerization
which resulted in the decrease of the number of propagating chains.
For BPO, the number of chains roughly corresponds to an apparent
initiator efficiency of 50% based on [BPO].sub.o in all cases. This
means that not all bromines were transferred from CuBr to polymer
head groups and may indicate the presence of both CuBr and
Cu(O.sub.2CPh) as activators. The low initiator efficiency may also
partially be ascribed to the aromatic substitution side reaction of
the benzoyloxy radical.
[0394] Homogeneous "reverse" ATRP can now be successfully carried
out, or initiated by, decomposition of either diazo compounds or
peroxides. For AIBN initiated polymerization, CuBr has little
effect while "reverse" ATRP occurs efficiently in the presence of
CuBr.sub.2 which can scavenge initiating/growing radicals and form
CuBr and RBr species. In contrast, CuBr.sub.2 is an inefficient
component of "reverse" ATRP initiated by BPO due to fast electron
transfer from the resulting Cu(I) to BPO and coordination of
benzoate anions to copper. However, the polymerization initiated by
BPO can be controlled in the presence of a sufficient amount of
CuBr. After the induced decomposition of BPO, growing radicals are
deactivated by Cu(II) species to produce bromine terminated
oligomers and Cu(I) species. Both Cu(O.sub.2CPh) and CuBr can then
successfully catalyze ATRP.
EXAMPLE 36
Charged Ligands
[0395] The different polymerization reactions using charged ligand
(1) as a catalyst and their conditions are listed in Table 27.
29TABLE 27 Results of polymerization reactions using charged ligand
1. Conditions (monomer/cat./AIBN/ Con. M.sub.n, exp. M.sub.n, theo.
Monomer entry anisole; temperature) Time (%) M.sub.w/M.sub.n
(10.sup.4 g/mol) (10.sup.4 g/mol) MA 1 500/1/0.5/50; 100.degree. C.
1 h 53 1.46 7.9 2.3 2 500/1/1/500; 90.degree. C. 21 h 52 2.0 3.7
2.2 3 200/1/0.25/0.125; 90.degree. C. 29.5 h 63 1.58 2.2 1.1 4
200/1/0.1/0.05; 70-90.degree. C. 44.5 h 34 2.02 0.5 0.3 MMA 5
500/1/0.5/50; 90.degree. C. 1.25 h 32 1.86 6.7 1.6 6 500/1/0.5/500;
60.degree. C. 22 h 11 1.55 2.3 0.6 7 500/1/0.5/500; 90.degree. C.
14 h 80 1.67 41.8 40 8 500/2/0.5/500; 90.degree. C. 14 h 14 1.66
1.3 0.7 9 500/3/0.5/500; 80.degree. C. 3 d 26 1.50 3.4 1.3 styrene
10 200/1/0.5/20; 110.degree. C. 23 h 66 2.52 3.5 1.4 11
200/3/0.5/50; 80.degree. C. 3 d 18 2.30 0.4 0.37
EXAMPLE 36a
Reversed ATRP with the Tripodal Charged Ligand-Cu(II)-Complex 2
[0396] 19
[0397] Complex 2 with a Tripodal Charged Ligand (X=Br, Cl)
[0398] In the polymerization reactions, the initial green and
insoluble complex 2 dissolved and the solutions turned yellow for
styrene and light green for MMA and MA. The complex 2 showed a good
activity in the polymerization of styrene and MMA but polymerized
MA slowly, Table 28. The polymerization reactions in anisole were
only achieved at 110.degree. C.
30TABLE 28 Results of the Polymerization Reactions with Complex 2
at 110.degree. C. and in 50% anisole Conditions monomer/cat./ Con.
M.sub.n, exp. M.sub.n, theo. Monomer AIBN/ Time (%) M.sub.w/M.sub.n
(10.sup.4 g/mol) (10.sup.4 g/mol) MMA 200/1/0.5 5.5 h 52 1.25 1.95
1.04 styrene 200/1/0.5 5.5 h 50 1.42 1.68 1.04 MA 200/1/0.5 21 h 42
1.18 0.48 0.72
[0399] As the polymerization of MMA in anisole at 110.degree. C.
showed a limiting conversion of 52% and the resulting polymer had a
molecular weight M.sub.n two times higher than the calculated one
M.sub.n,theo it was the goal to work out better conditions for this
polymerization. The different approaches with their conditions are
listed in Table 29.
31TABLE 29 Results of the Polymerization Reactions of MMA with
Complex 2 at 110.degree. C. and in 50% anisole Conditions
monomer/cat./ T Time Con. M.sub.n, exp. M.sub.n, theo. Solvent
AIBN/BPN (oC) (h) (%) M.sub.w/M.sub.n (10.sup.4 g/mol) (10.sup.4
g/mol) anisole 200/1/0.55/0 90 no polymerization anisole
200/1/0.55/0 110 5.5 52.sup.2) 1.25 1.95 1.04 anisole
200/0.2/0.11/1 90 no polymerization anisole 200/1/0.55/0 +
Cu.sup.1) 110 redox-initiated polymerization anisole 200/0.2/0.11/1
110 1 40.sup.2) 1.25 0.76 0.80 xylole 200/1/0.55/0 90 no
polymerization xylole 200/1/0.55/0 110 4 77 1.62 3.14 1.54
1,4-dimethoxy- 200/1/0.55/0 90 4.5 90 1.63 3.27 1.80 benzene
1,4-dimethoxy- 200/0.2/0.11/1 90 4 40.sup.2) 1.23 8.13 8.00 benzene
proprionitril 200/1/0.55/0 90 redox-initiated polymerization
ethylene 200/1/0.55/0 90 2 49 1.28 2.16 0.98 carbonate methyl-
200/1/0.55/0 90 4.sup.3) 64 1.52 3.19 1.28 pyrrolidinone DMF
200/1/0.55/0 90 5.sup.3) 64 1.64 3.36 1.28 .sup.1)addition of 2 eq.
Cu(0) .sup.2)limiting conversion .sup.3)induction period 120
min
[0400] The use of other solvents, which are listed above, have an
dramatic effect on the polymerization behavior and some permit the
polymerization at 90.degree. C.
EXAMPLE 37
Polyethylene Graft Copolymers
[0401] Earlier in this application the preparation of novel graft
copolymers, wherein the graft (co)polymer was attached to the
backbone (co)polymer within the grafted polymer chain, was
disclosed; we would now like to describes the some advances in the
case of normal graft copolymers through modification of, and
subsequent polymerization from, poly(ethylene-co-glycidyl
methacrylate). Ring-opening of the epoxide groups with chloroacetic
acid is described along with subsequent polymerization with styrene
and benzyl acrylate. Details on the hydrolysis of the benzyl groups
in the latter copolymer toward synthesis of amphiphillic graft
copolymers are also taught.
[0402] Materials Poly(ethylene-co-glycidyl methacrylate)
(P(E-co-GMA)) containing 8% (wt.) GMA units, chloroacetic acid and
chlorobenzene were used as received from Aldrich. Styrene and
benzyl acrylate, from Aldrich, were distilled from calcium hydride
and calcium chloride, respectively, prior to use. Copper chloride
(CuCl) was washed with glacial acetic acid, washed with absolute
ethanol and dried under vacuum. 4,4'-Di-nonyl-2,2'-bipyridine
(dNbpy) was synthesized by a previously reported procedure.
[0403] Measurements FTIR spectra of polymer films cast on Teflon
were recorded with a ATI Mattson Infinity Series FTIR. Monomer
conversion was measured on a Shimadzu GC-14A gas chromatograph
equipped with a wide-bore capillary column (DB-Wax, J&W Sci.).
The composition of the purified samples were measured by .sup.1H
NMR on a 300 MHz General Electric GN 300 spectrometer with variable
temperature capability using Tecmag data acquisition software. Size
exclusion chromatography (SEC) measurements in THF were carried out
using a Waters 510 liquid chromatograph pump equipped with four PSS
columns (100 .ANG., 1000 .ANG., 10.sup.5 .ANG. and guard) in series
with a Waters 410 differential refractometer. Molecular weight
analyses were calculated with PSS software; calibration based on
low polydispersity polystyrene standards. Differential scanning
calorimetry (DSC) data was obtained from a Rheometrics DSC Plus.
Elemental analyses were measured by Midwest Microlabs.
EXAMPLE 37a
Synthesis of the Macroinitiator
[0404] P(E-co-GMA) (5.0 g, 3.8 mmol GMA), chloroacetic acid (0.30
g, 3.2 mmol) and 100 ml xylene were heated to 115.degree. C. under
argon and stirred until the polymer completely dissolved.
Tetrabutylammonium hydroxide (0.28 mmol) in 0.72 ml ethanol was
added and the reaction was stirred at 115.degree. C. for 43 hours.
The hot solution was precipitated into excess methanol and
collected by filtration. The product was reprecipitated into
methanol from hot xylene. The white powder was isolated and dried
under vacuum. Elemental analysis showed that 51% of the GMA groups
had been functionalized.
EXAMPLE 37b
Graft Polymerizations
[0405] For the ATRP of styrene, 0.2 g (7.4.times.10.sup.-2 mmol Cl)
of the macroinitiator, 7.3 mg (0.74 mmol) CuCl and 60 mg (0.15
mmol) dNbpy were placed into three glass ampoules and degassed by
three vacuum/argon cycles. To each tube, 1.0 ml (8.7 mmol styrene)
of 5% chlorobenzene in styrene was added. The tubes were sealed
under vacuum and placed into a 130.degree. C. oil bath. The tubes
were removed periodically. The reaction mixtures were placed in
vials with benzene for conversion measurements by GC. The products
from each tube were purified by two precipitations from solutions
of hot toluene into methanol. The white powders were dried at room
temperature under vacuum.
[0406] The ATRP of benzyl acrylate was performed in the drybox to
facilitate removal of kinetics samples. 0.5 g (20 mmol Cl)
Macroinitiator, 2.0 g (12 mmol) benzyl acrylate and 2.5 g of
toluene were placed into a 50 ml round bottom flask and stirred at
90.degree. C. until a finally dispersed mixture formed. To this, a
solution of 10 mg (0.10 mmol) CuCl, 82 mg (0.20 mmol) dNbpy, 1.2 g
(7.4 mmol) benzyl acrylate and 0.7 g toluene was added to the
reactor. The maroon liquid was stirred at 90.degree. C. for one
minute to ensure that all macroinitiator dissolved at which time
the first kinetics sample was removed. Subsequent samples were
removed periodically from the reaction. Products were isolated from
each sample by precipitation from hot toluene solutions into
methanol. The white powders were dried at room temperature under
vacuum.
EXAMPLE 37c
Cleavage of Polystyrene Grafts
[0407] 0.1 g of poly(ethylene-g-styrene) was placed into a 50 ml
round bottom flask with 10 ml THF and 0.45 ml of 1 M
tetrabutylammonium hydroxide solution in methanol. The solution was
stirred under reflux for 16 hours. Upon cooling to room
temperature, the polyethylene precipitated from solution. The
liquid phase was removed, neutralized with hydrochloric acid and
injected onto the SEC chromatograph for molecular weight
determination of the polystyrene. This method served to cleave the
ester groups of the functionalized glycidyl methacrylate and
acetate moieties. The molecular weight of the polystyrene chains
increased with monomer conversion during the polymerization and
polydispersities were low, M.sub.w/M.sub.n<1.4. These reactions
were consistent with a similar system where the homopolymerization
of styrene from vinyl chloroacetate occurred under control and with
high initiation efficiency. Examination of the SEC chromatograms in
clearly confirmed that the growth of polystyrene proceeded under
control; the entire peak shifted to higher molecular weight with
increasing extent of reaction.
EXAMPLE 37d
ATRP of Benzyl Acrylate
[0408] While the use of a drybox is not generally required for
ATRP, one was used in this case to facilitate greater ease in
removal of samples. Samples could not be removed by a needle as in
many typical ATRP procedures because the polyethylene would
precipitate as the temperature of the reaction decreased.
Therefore, in a drybox the cover to the reactor was removed without
concern for contamination by oxygen and samples were extricated
with a wide bore syringe or glass pipette.
[0409] The reaction was run in 50% toluene in benzyl acrylate at
90.degree. C. using 0.5 equivalents of CuCl(dNbpy).sub.2 relative
to chloroacetate groups. The ratio of monomer to chloroacetate was
100. As the reaction proceeded, the swellability of the polymers in
xylene increased indicating incorporation of a segment whose
homopolymer is soluble in that solvent. FTIR spectroscopy of a film
of the purified material showed and intense carbonyl stretch at
1736 cm.sup.-1 indicating the presence of the acrylate in the
copolymer. An attempt to cleave the grafted chains using the method
described above for styrene was not made due to competing
hydrolysis of the benzyl ester groups.
[0410] Herein the modification of a commercially available
poly(ethylene-co-glycidyl methacrylate) into an ATRP macroinitiator
by reaction with chloroacetic acid had been detailed. The pendant
functionalized polyolefin was used for the controlled
polymerization of styrene and benzyl acrylate. In both cases,
incorporation of the vinyl monomer into the copolymer increased
with extent of reaction.
EXAMPLE 37e
Methyl Methacrylate Grafted Polyethylene by ATRP: Preparation of
the Macroinitiator with Bromo Isobutyryl Groups
[0411] In order to be able to graft methacrylates onto
polyethylene, a macroinitiator with bromo isobutyryl groups was
prepared by the reaction of poly(ethylene-co-GMA) copolymer with
bromoisobutyric acid (BIBA), catalyzed by tetrabutylammonium
hydroxide (TBAH). The copolymer (10 g, 7.75.times.10.sup.-3 mole
GMA), BIBA (2.6 g, 15.5.times.10.sup.-3 mole) and 150 ml o-xylene
were heated at 115.degree. C., under nitrogen. After the polymer
dissolved, 0.8 ml TBAH 1 M in methanol (7.75.times.10.sup.-4 mole)
was added, and the reaction mixture was stirred at 115.degree. C.
for 38 hr. The final yellowish mixture was poured into a large
excess of methanol in order to recover the polymer. The
macroinitiator was purified by 2 more precipitation from hot
toluene into methanol. The final product was dried under vacuum.
The elemental analysis showed the following composition: C=79.92%;
H=13.13%; Br=3.90%; O=3.15%.
[0412] Synthesis and characterization of P(E-g-MMA) copolymer. The
macroinitiator prepared as described was used to initiate MMA
polymerization. The polymerization was performed in xylene
solution, MMA/xylene=1/2, at 90.degree. C., in tubes, under
nitrogen. Br/CuCl/dNbpy=1/1/2. target M.sub.n,grafts=20K The
catalyst solution in xylene/MMA was prepared in a Schlenk flask,
under nitrogen, and then transferred via argonated syringes into
tubes containing the macroinitiator under nitrogen. The tubes were
sealed and placed in the oil bath at 90.degree. C. At certain time
intervals, tubes were withdrawn from the oil bath, cooled down and
the content was transferred to 20-ml vials by using THF as
dispersant. All samples were heated up in order to dissolve in THF,
and then left to cool down (separation occurred). All samples were
soluble in hot THF. Conversion were determined after that by GC,
using xylene as internal standard and increased linearly with time
showing a controlled polymerization.
[0413] The .sup.1H NMR spectra of the purified polymerization
products displayed peaks for both polyMMA (.delta.=3.4 ppm
--OCH.sub.3; 2.1 ppm --CH.sub.2--C(CH.sub.3)--; 1.3 ppm
--CH.sub.2--C(CH.sub.3)--) and polyethylene (.delta.=1.4 ppm)
segments (FIG. 20), demonstrating the formation of the graft
copolymer.
[0414] As conversion increased, the amount of MMA in the graft
copolymer increased as well (Table 30). The MMA content of
P(E-g-MMA) was determined by .sup.1H NMR, using the area of the
triplet at .delta.=3.4 ppm versus the area of the peaks at
.delta.=1.2-1.5 ppm, and also calculated from monomer conversion.
The two sets of copolymer compositions agreed very well.
32TABLE 30 Conversion and composition data for the ATRP of MMA from
PEBr.sup.a) Time Conversion MMA content.sup.b) MMA content.sup.c)
Sample (min) (%) (wt. %) (wt. %) 1 90 9 45 47 2 180 20 67 66 3 330
34 77 77 4 480 43 80 81 .sup.a)[MMA].sub.o = 3.12 M;
[2-bromoisobutyrate].sub.o = [CuCl].sub.o = [dNbpy].sub.o/2 = 15.6
mM; solvent o-xylene, 90.degree. C.; .sup.b)determined by
.sup.1HNMR; .sup.c)calculated from MMA conversion
[0415] DSC analysis of the P(E-g-MMA) samples showed the presence
of the glass transition of polyMMA grafts (about 125.degree. C.),
indicative for the phase separation. The glass transition
temperature of polyMMA was more visible in samples with MMA content
above 67 wt %.
EXAMPLE 38
ATRP of MMA-POSS
[0416] To a glass tube with magnetic stir bar was added, MMA-POSS
(200 mg, 0.194 mmol), initiator (10-mol % relative to monomer),
Cu(I)Cl (0.0097 mmol), PMDETA (2.0 .mu.L, 0.0097 mmol ) and
degassed 1,2-dichlorobenzene (50-wt % relative to monomer). The
tube was evacuated while under liquid nitrogen for three freeze,
pump, thaw cycles and sealed under vacuum. The tube was then placed
in an oil bath at 70.degree. C. for 42 hrs. Polymer was recovered
by precipitation into methanol (10-fold excess). From SEC analysis
(in toluene against linear PS), the synthesis of low molar mass
polymer with low polydispersity was confirmed (M.sub.n=9,590;
M.sub.w/M.sub.n=1.14). The M.sub.n SEC was significantly lower than
theoretical predictions (M.sub.n theoretical=14,790) and was
attributed to hydrodynamic volume differences between p(MA-POSS)
and linear PS standards.
EXAMPLE 39
Synthesis of poly(MMA-POSS) Block Copolymers
[0417] To a glass vial with a magnetic stir bar was added, MMA-POSS
(200 mg, 0.194 mmol), initiator (10-mol % relative to monomer),
Cu(I)Cl (0.0097 mmol). The vial was fitted with rubber septum and
evacuated/back-filled with argon (three times). Degassed toluene
(50-wt % relative to monomer and macroinitiator) was added via
syringe. PMDETA (2.0 .mu.L, 0.0097 mmol ) was added last, via
syringe. The reaction flask was then placed in an oil bath at
60.degree. C. for 24 hrs. Polymers were recovered by precipitation
into methanol (10-fold excess).
EXAMPLE 40
ATRP of Sty-POSS and Styrene
[0418] A similar procedure was used a for the ATRP of MMA-POSS
except with: Sty-POSS (503 mg, 0.5 mmol), phenylethyl bromide (7.0
.mu.L, 0.05 mmol), Cu(I)Br (3.6 mg, 0.025 mmol), PMDETA (5.3 .mu.L,
0.025 mmol), styrene (471 mg, 4.5 mmol) and benzene (981 mg, 12.5
mmol) at 80.degree. C.
[0419] In a further experiment Sty-POSS was homopolymerized using a
bromine-terminated, difunctional p(n-BA) macroinitiator (M.sub.n
SEC=2300; M.sub.w/M.sub.n=1.3). For this system, a Cu(I)Br/PMDETA
catalyst was used, in a toluene solution (50-wt % relative to
monomer/macroinitiator) under the following conditions:
[0420] [M]:[I]:[Cu(I)Cl]:[PMDETA]=0.39 M: 0.019 M: 0.011 M: 0.011 M
at 110.degree. C.
EXAMPLE 41
Synthesis of Homopolymer Diblock and Random Copolymers of
POSS-Materials
[0421] The synthesis of p(MMA-POSS) homopolymer was conducted using
ethyl-2-bromoisobutyrate as an initiator. Low DP.sub.n's were
targeted and a monomer conversion of p=0.50, was obtained, as
determined by .sup.1H NMR analysis. AB diblock copolymers were
synthesized by the application of a monofunctional poly(n-butyl
acrylate) macroinitiator (M.sub.n=2200, M.sub.w/M.sub.n=1.3) to the
polymerization of MMA-POSS. From the SEC analysis, efficient chain
extension from the macroinitiator was observed. Additionally,
random copolymers of styrene and Sty-POSS were also prepared at a
feed ratio of 9:1, of the respective monomers. The incorporation of
Sty-POSS into the growing polymer was found to be constant, as
determined by .sup.1H NMR analysis at various monomer conversions.
All of the polymerizations were done in 1,2-dichlorobenzene, or
toluene as a solvent, because the POSS-monomers (M.sub.n>1000)
were solids at room temperature. The SEC chromatograms of the
aforementioned polymers are presented in Table 31.
33TABLE 31 POSS-based Homopolymers and Copolymers Synthesized by
ATRP Polymer/Composition M.sub.n M.sub.w/M.sub.n
p(MMA-POSS)/homopolymer 4,620* 1.08 p(BA)-b-p(MMA-POSS)/diblock
copolymer 5,840* 1.18 p(Sty)-r-p(Sty-POSS)/random copolymer
15,750.sub..xi. 1.30 *Apparent molar mass determined by SEC in THF
against linear PMMA .sub..xi.Apparent molar mass determined by SEC
in THF against linear Psty
EXAMPLE 42
Synthesis of Star Block and Triblock Copolymers from MMA-POSS
[0422] As alluded to earlier, the synthesis of block copolymers
with hard segments of POSS-based polymers and soft segments of
another polymer with a low T.sub.g, is an area of great interest
towards the preparation of thermoplastic elastomers. Thus, star
block and ABA triblock copolymers with hard, p(MMA-POSS) segments
at the periphery were prepared. The synthesis of star block
copolymers was conducted by the application of a three-armed
poly(methyl acrylate) macroinitiator (M.sub.n=7,900,
M.sub.w/M.sub.n=1.10) to the ATRP of MMA-POSS. In the block
copolymer synthesis, a DP.sub.n=20 was also targeted for the chain
extension reaction. The SEC chromatogram (SEC in THF, against
linear PMMA), indicated a well-defined block copolymer containing
p(MMA-POSS) was prepared.
[0423] Additionally, ABA triblocks were made by the use of a
difunctional p(BA) macroinitiator (M.sub.n=11,000,
M.sub.w/M.sub.n=1.16) in the ATRP of MMA-POSS. For the chain
extension reaction of MMA-POSS from a p(BA) macroinitiator, a
DP.sub.n=20 was targeted. From the SEC chromatogram (in THF against
linear pMMA) an increase in molar mass in the ATRP of MMA-POSS from
the macroinitiator was observed.
[0424] From .sup.1H NMR analysis of the block copolymers, the
incorporation of p(MMA-POSS) was verified.
[0425] In the polymerizations of MMA-POSS toward the synthesis of
ABA triblocks and star block copolymers, monomer conversion was
determined by consumption of vinylic protons (.delta.=5.6, 6.1
ppm), as observed in the .sup.1H NMR spectra. Analysis of the
unprecipitated reaction mixtures revealed that vinyl bonds were
consumed to high conversions (p>0.95). Resonances for
cyclopentyl protons associated with the POSS cube were observed at
.delta.=0.6, 1.0, 1.6 and 1.8 ppm and overlapped with resonances
from the polymer backbones of p(MA) and p(BA) macroinitiators. For
the pMA-b-p(MMA-POSS) star block copolymer methoxy protons were
observed at .delta.=3.8, while for the
p(MMA-POSS)-b-pBA-b-p(MMA-POSS) triblock copolymers, methylene
protons were seen at .delta.=4.1 ppm. Additionally, resonances at
.delta.=3.9 from the methylene protons of the p(MMA-POSS)
components were observed, indicative of successful chain extension
from the polyacrylate macroinitiators.
[0426] The synthesis of triblock copolymers with
p(MA-POSS)-r-p(MMA) hard segments was also conducted. This material
has the potential advantage of possessing enhanced physical
properties from incorporation of POSS components, while cutting the
total amount of POSS that needs to be used. This is a direction of
great practical interest, due to the current high cost of
POSS-monomers.
[0427] The experimental approach was identical to that used in the
synthesis of p(MA-POSS)-b-p(BA)-b-p(MA-POSS), where a difunctional
pBA macroinitiator (M.sub.n=13,750; M.sub.w/M.sub.n=1.18) was
employed in a 50-wt % solution of toluene. A 1:1 molar feed ratio
of MA-POSS to MMA was used to prepare hard segments around the pBA
macroinitiator. NMR analysis revealed the incorporation of both MMA
and MA-POSS onto the macroinitiator however determination of the
monomer conversions was difficult due to overlapping resonances.
GPC showed the presence of some unreacted MA-POSS but the M.sub.n
of the block copolymer has increased to 24,050.
EXAMPLE 43
Particles Possessing Appropriate Functionality for Controlled
ATRP
[0428] The general procedure for the synthesis of functional
particles from the Stober process was as follows:
[0429] TEOS (8 mL, 35 mmol) was added to a stirring solution of
absolute ethanol (120 mL) and the appropriate concentration of
ammonium hydroxide (aq.) (7.4 mL) and was allowed to stir for seven
hours, yielding a white, turbid suspension. To prepare coated
particles, a functional trialkoxysilane (1 mL) was added via
syringe to a 35 mL aliquot of the alcosol prepared from TEOS and
allowed to adsorb on the particle surfaces for 30 min. The
suspension was then slowly concentrated (10 mL distilled over 2
hours) to drive condensation reactions of functional silane to the
silica particles. Isolation of the particles was conducted by
stripping of solvent from the already concentrated alcosol of
coated particles to a volume of 5-10 mL, precipitation into heptane
(10-fold excess), followed by centrifugation (3000 rpm) for 2 hrs.
The resulting product was initially a white gel, which after drying
yielded a white solid. (10% yield) The particles were then
suspended in toluene (5 mL) treated with hexamethyldisilazane (1.0
mL, 4.7 mmol) to end-cap residual silanol groups, however, this
treatment did not improve the solubility of the particles. And
after isolation of the particles in the solid state, dissolution in
non-polar (THF, toluene) and polar solvents (methanol, ethanol) was
not possible.
[0430] As described earlier in the discussion, particle sizes of
the colloidal silica, prepared from the Stober process, were
controlled by using various concentrations of ammonium hydroxide.
Table 32, lists the experiments that were conducted, along with the
concentration of ammonium hydroxide and the resulting particle
sizes that were achieved.
34TABLE 32 Summary of Conditions for Preparation of Functional
Stober Particles Concentration of Particle Size Experiment #
NH.sub.4OH (from TEM) Functional Silane JP-6-54 20 N .about.60 nm
MPS (methacrylate) JP-6-62 5 N .about.6-10 nm MPS (methacrylate)
JP-6-64 5 N .about.6-10 nm BIB-TMS (bromoisobutyrate)
[0431] While the coating of colloidal silica MPS was successful,
isolation of the particles, was problematic, as evidenced by the
limited solubility of the coated particles after recovery from
precipitation into heptane. Methacrylate particles prepared from
the Stober process yielded turbid dispersions after the coating
process, while still in the presence of ammonium hydroxide. Thus,
the tuning of the particle sizes of the colloidal silica was
achieved by using 20 N and 5 N concentrations of ammonium
hydroxide. In both cases, the addition of a large excess of toluene
to the coated colloidal dispersion did not result in precipitation,
indicative that particles were capable of being redispersed in
organic solvents. TEM measurements confirmed that particle sizes of
the coated silica particles were greatly affected by the
concentration of ammonium hydroxide. From the TEM micrographs, the
presence of discrete nanoscale spheres were observed, revealing
that large scale aggregation of particles did not occur.
Additionally, .sup.29Si CP-MAS NMR of particles from JP-6-54
clearly showed the presence of "T"-resonances for silicon-carbon
bonds in the region of -40 to -60 ppm, in addition to "Q"
resonances at -90 to -110 ppm, which is indicative of successful
surface treatment of the particles.
[0432] The synthesis of bromoisobutyrate functional particles was
also accomplished using the Stober process, but initially yielded
unstable dispersions and aggregated particles. To prepare
bromoisobutyrate functional particles, 3-(2-bromoisobutyryloxy)
propyltrimethoxysilane (BIB-TMS) was added to a colloidal
dispersion of silica. However, upon addition of BIB-TMS to the
dispersion, immediate coagulation of the silica colloids was
observed, as evidenced by the formation of a white precipitate. The
destabilization was presumably due to the hydrophobicity of the
BIB-TMS monomer. Despite the precipitation, characterization of the
particles was conducted. TEM of the particles also showed the
presence of discrete particles around 6-10 nm in diameter.
Additionally, the .sup.29Si CP-MAS NMR of the particles also
confirmed the coating of silica colloids with BIB-TMS. However, as
in the case of the methacrylate particles, the limited solubility
of the particles strongly implies that some small-scale aggregation
took place, preventing complete dissolution of the particles in
organic solvents (THF, toluene, ethanol, methanol).
[0433] The general procedure for the synthesis of particles from
this approach is presented below: methyltrimethoxysilane (2.56 mL,
18.3 mmol) was added slowly over a 45 minute period to a solution
of 6 mM NaOH (12.5 mL) and benzethonium chloride (6-30 wt %
relative to trialkoxysilane) and then allowed to stir for 5 hours.
Methoxytrimethylsilane (0.8 mL, 5.8 mmol) was then added and the
reaction was allowed to proceed overnight. The reaction was then
precipitated into methanol, and the solid was recovered by
centrifugation. The white solid was then resuspended in toluene (5
mL) and hexamethyldisilazane (0.8 mL, 1.5 mmol) and allowed to
react overnight. Particles were recovered by precipitation into
methanol and filtration.
[0434] The synthesis of trimethylsilyl functional particles was
first conducted using both 6%-wt of and 12.2%-wt of benzenthonium
chloride (surfactant). Using the aforementioned conditions,
particles prepared from the 6%-wt of benzethonium chloride system
were found to be insoluble in organic solvents and displayed a
significant amount of aggregation in the TEM micrographs. While
large scale aggregation was observed by TEM in this system, it
should be noted the spherical particles (6-10 nm) were still
present. This result implied that additional surfactant was
required to stabilize particle formation. By doubling the wt % of
surfactant (12.2%-wt), particles that were completely soluble in
THF and toluene were prepared. Solutions of the particles were also
able to be passed through 0.2 micron PTFE filters. TEM of these
particles was not conducted, however, spherical particle formation
as seen in micrographs from the 6%-wt experiment, along with the
solubility properties of the particles, imply that the synthesis
was successful. TEM characterization is pending. TGA analysis
revealed that over 80%-wt of the material was still present above
800.degree. C., indicating the presence of silicate networks.
EXAMPLE 44
ATRP of Acrylamides
[0435] A series of experiments has determined that the ligand to be
used for the polymerization of acrylamides should be pure and that
final conversion was dependant on the amount of CuCl added to the
system.
EXAMPLE 44a
DMAA Polymerization Using Different Amounts of CuCl
[0436] The target M.sub.n was 10K. The experiment was performed in
tubes, without stirring, at room temperature, under nitrogen. The
results are displayed in Table 33.
35TABLE 33 DMAA polymerization with different amounts of CuCl
MCP/CuCl/ Time Exp. Me.sub.6Tren hr Conv. % M.sub.n,th M.sub.n
M.sub.w/M.sub.n DMAA70-1 1/1/1 14.5 59 5900 5820 1.12 70-2 1/2/1
14.5 82 8200 8650 1.20 70-3 1/3/1 14.5 24.4 2440 2940 1.17 70-4
1/4/1 14.5 17 1700 1990 1.50
EXAMPLE 44b
DMAA Polymerization with Me.sub.6Tren--Sequential Addition of
CuCl
[0437] In order to check if higher yields can be reached by using
an excess of CuCl, the transition metal compound was added
sequentially, while the amount of Me.sub.6Tren was kept constant.
Each CuCI portion was equal with the amount of Me.sub.6Tren
introduced initially. The results are displayed in Table 34.
36TABLE 34 DMAA polymerization with different amounts of CuCl -
sequential addition MCP/CuCl/ Time Conv. Me.sub.6Tren hr %
M.sub.n,th M.sub.n M.sub.w/M.sub.n Remarks 1/1/1 8.5 69 6900 7100
1.07 initially introduced 1/2/1 23.17 82.4 8240 8350 1.12 1st
additional portion of CuCl 1/3/1 33 81.8 8180 7900 1.11 2nd
additional portion of CuCl 1/4/1 47.17 80.7 8070 7800 1.11 3rd
additional portion of CuCl
[0438] The reaction was carried out at room temperature, in a
Schlenk flask, under nitrogen, with stirring.
[0439] These results show that the limiting conversion depends on
the catalyst to initiator ratio.
EXAMPLE 45
Acrylamide Polymerization
[0440] For the polymerization of DMAA the polarity of the solvent
influences the limiting conversion. More polar solvents decreases
the limiting conversion (Table 35).
37TABLE 35 DMAA polymerization - influence of the solvent Time
Conv. Exp. Solvent (h) (%) M.sub.n M.sub.w/M.sub.n DMAA78 toluene
22.25 56 6860 1.11 DMAA85-1 ethyl acetate 16.5 40.6 4080 1.10
DMAA85-2 dichlorobenze 16.5 21 2860 1.14 ne DMAA94K DMF 21.85 44
5980 1.17 Exp. cond.: DMAA/solvent = {fraction (1/3;)} target
M.sub.n = 10 K; MCP/CuCl/Me.sub.6Tren =1/1/1; rt.
[0441] No precipitate was observed in dichlorobenzene and DMF,
while the precipitate formed when toluene and ethyl acetate were
used as solvents.
[0442] By adding Cu.sup.0 the limiting conversion increased, but
the increase was small (Table 36). The final reaction mixtures were
green and free of precipitate (only unreacted Cu.sup.0).
38TABLE 36 DMAA polymerization in the presence of Cu.sup.0 Time
Conv. Exp. CuCl/Cu.sup.0 (h) (%) M.sub.n M.sub.w/M.sub.n DMAA78 1/0
22.25 56 6860 1.11 DMAA79 1/1 16 69 8000 1.16 DMAA81-1 1/3 19.5 75
9070 1.17 DMAA81-2 1/5 19.5 76 9080 1.17 Exp. cond.: DMAA/toluene =
1/3; target M.sub.n = 10K; MCP/CuCl/Me.sub.6Tren = 1/1/1; Cu.sup.0
= powder, dendritic, 3 microns; 99.7%
EXAMPLE 45a
Addition of Excess Transition Metal Compound
[0443] By adding CuCl in excess, the limiting conversion increases
at the beginning (MCP/CuCl=1/2), and then decreases (Table 37). A
too large excess of CuCl actually shut down the reaction.
39TABLE 37 DMAA polymerization with different amounts of CuCl-one
pot addition MCP/CuCl/ Time Conv. Exp. Me.sub.6Tren hr % M.sub.n,th
M.sub.n M.sub.w/M.sub.n DMAA70-1 1/1/1 14.5 59 5900 5820 1.12 70-2
1/2/1 14.5 82 8200 8650 1.20 70-3 1/3/1 14.5 24.4 2440 2940 1.17
70-4 1/4/1 14.5 17 1700 1990 1.50 Target M.sub.n = 10K;
DMAA/toluene = 1/3; RT.
EXAMPLE 45b
Intermittent Addition of Transition Metal Compound
[0444] Sequential addition of CuCl led to an increase of conversion
and molecular weight, showing that active end groups were present
at the limiting conversion stage.
40TABLE 38 DMAA polymerization with different amounts of CuCl -
sequential addition MCP/CuCl/ Time Conv. Me.sub.6Tren hr %
M.sub.n,th M.sub.n M.sub.w/M.sub.n Remarks 1/1/1 8.5 69 6900 7100
1.07 initially introduced 1/2/1 23.17 82.4 8240 8350 1.12 1st
additional portion of CuCl 1/3/1 33 81.8 8180 7900 1.11 2nd
additional portion of CuCl 1/4/1 47.17 80.7 8070 7800 1.11 3rd
additional portion of CuCl Target M.sub.n = 10K; DMAA/toluene =
1/3; RT.
EXAMPLE 45c
Intermittent Addition of Reagents/Reactants
[0445] Addition of a new portion of catalyst (CuCl/Me.sub.6TREN)
dissolved in monomer, after a time interval long enough to reach
the limiting conversion stage, led to an increase of the molecular
weight (Table 39). After 6.45 h a precipitate formed in the
reaction mixture, which dissolved when the second portion of
catalyst dissolved in monomer was added.
41TABLE 39 Chain extension experiment by addition of
CuCl/Me.sub.6Tren dissolved in monomer MCP/CuCl/ Me.sub.6Tren Time
Conv. Sample cumulative (h) (%) M.sub.n M.sub.w/M.sub.n 1 1/1/1
8.25 51 6100 1.11 2 1/2/2 23.16 -- 7100 1.14 3 1/3/3 31.5 -- 7300
1.21 initially: target M.sub.n = 10K; DMAA/toluene = 1/3; RT; the
second and the third portion of catalyst were dissolved in 1/3 the
initial volume of monomer.
EXAMPLE 45d
Addition of Redox Conjugate
[0446] Increasing amounts of CuCl.sub.2 added from the very
beginning to the reaction mixture largely slowed down the
polymerization (Table 40). All samples were homogeneous at the
beginning of the polymerization. The time interval after which the
precipitate forms seems to depend on the amount of CuCl.sub.2
added. The larger the amount of CuCl.sub.2, the lower the time
interval is.
42TABLE 40 DMAA polymerization - influence of CuCl.sub.2
CuCl/CuCl.sub.2/ Time Conv. Exp. Me.sub.6Tren (h) (%) M.sub.n
M.sub.w/M.sub.n DMAA78 1/0/1 22.25 56 6860 1.11 DMAA87-1 1/0.1/1.1
22 28.9 3650 1.10 DMAA87-2 1/0.2/1.2 22 21.7 3000 1.10 DMAA96-1
1/0.3/1.3 21.75 18.5 2450 1.11 DMAA96-2 1/0.4/1.4 21.75 9.5 1540
1.09 DMAA97 1/0.5/1.5 22 6.1 1250 1.06 Exp. cond.: DMAA/toluene =
1/3; target M.sub.n = 10K; MCP/CuCl/Me.sub.6Tren = 1/1/1; rt.
EXAMPLE 45e
Addition of Initiator
[0447] A new portion of initiator added at the limiting conversion
stage failed to produce polymer (Table 41). Therefore, at the
limiting conversion stage there is no active catalyst present.
43TABLE 41 DMAA polymerization - sequential addition of the
catalyst MCP/catalyst Time Conv. Sample cumul (h) (%) M.sub.n
M.sub.w/M.sub.n DMAA93-1 1/1 7 55.3 6900 1.12 DMAA93-2 2/1 21.25 57
7000 1.11 Exp. cond. (initial): DMAA/toluene = 1/3 v/v; target
M.sub.n = 10K; MCP/CuCl/Me.sub.6Tren = 1/1/1; RT.
[0448] RT.
EXAMPLE 45f
Analysis of End Groups
[0449] Polymerization performed in the NMR tube, using deuterated
toluene as a solvent, under different conditions, showed that the
active chain end groups are partially lost during the
polymerization. However, the results seems to indicate that there
is not a direct correlation between conversion and the decrease of
the end group functionality, which may indicate the presence of a
side reaction leading to the lost of the end groups (Tables 42-44).
All conversions are a little overestimated due to the overlapping
of the polymer peaks with the toluene peak at 2.09 ppm.
44TABLE 42 DMAA polymerization - NMR experiment. DMAA/deut. toluene
= 1/3 v/v; target M.sub.n = 1000; MCP/CuCl/Me.sub.6TREN =
1/0.2/0.2. Temp: 37.degree. C.-5.5 h; then RT Time Cl end groups
No. (min) (%) Conversion DMAA89K-1 5 90 26 DMAA89K-2 10 87 29.5
DMAA89K-3 17 81 28 DMAA89K-4 25 84 26 DMAA89K-5 40 84 28 DMAA89K-6
90 72 26.5 DMAA89K-7 180 67 28 DMAA89K-8 200 69 DMAA89K-9 317 70 32
DMAA89K-10 1720 66 30 (28 h 40 min) DMAA89K-11 2970 65 33.3 (49.5
h) DMAA89K-12 7440 72 52 (124 h) DMAA89K-13 19050 70 67 (317.5 h)
After 5.5 h the sample was green and it contained a precipitate.
The final polymer had M.sub.n = 1330 and M.sub.w/M.sub.n =
1.12.
[0450]
45TABLE 43 DMAA polymerization - NMR experiment. DMAA/deut. toluene
= 1/3 v/v; target M.sub.n = 1000; ClDMAA/CuCl/Me.sub.6TREN =
1/0.2/0.2. Temp: 37.degree. C.-5 h; then RT Time Cl end groups No.
(min) (%) Conversion DMAA98K-1 6 82 37 DMAA98K-2 13 80 41 DMAA98K-3
22 76 41 DMAA98K-4 30 79 43 DMAA98K-5 60 74 41 DMAA98K-6 120 72 44
DMAA98K-7 212 63 45 DMAA98K-8 300 63 46 DMAA98K-9 1825 64 51
DMAA98K-10 10495 71 78 DMAA98K-11 20245 64 79
[0451] After 5 h the sample was green and it contained a small
amount of precipitate. The final polymer had M.sub.n=1500 and
M.sub.w/M.sub.n=1.14.
46TABLE 44 DMMA polymerization-NMR experiments. Higher molecular
weights targeted. DMAA/deuterated toluene = 1/3 v/v; RT. Target
Initiating Time Conv. Exp. M.sub.n system (h) (%) f.sub.terminal
halogen DMAA99-1 5000 MCP/CuCl/Me.sub.6Tren 7.33 79 -- 1/1/1 23 81
-- 122 83 -- DMAA99-2 5000 MBP/CuBr/Me.sub.6Tren 7.75 30 -- 1/1/1
26 36 -- 124 38 -- DMAA100 5000 ECP/CuCl/Me.sub.6Tren 7 74 0.43
1/1/1 24.5 74 0.35 166.5 79 0.16 DMAA101-1 2500
ECP/CuCl/Me.sub.6Tren 6.5 80 0.43 1/1/1 22 81 0.32 142.5 94 0.2
DMAA101-2 10000 ECP/CuCl/Me.sub.6Tren 7.25 53 0.38 1/1/1 24 53 0.06
148 54 --
[0452] The first measurement was performed after the limiting
conversion stage was reached, because usally 500 scans were
necessary to see the end groups (larger molecular weight than
previously). Remarks: DMAA99-1 exp.: no precipitate after 23 h;
DMAA 99-2: precipitate formed after 1.5 h; DMAA99-1,2-end group
functionality could not be determined because of the overlapping of
the signal due to CH.sub.3O that of the polymer.
EXAMPLE 46
Block Copolymers of Acrylamides
[0453] Poly(methyl acrylate) with chlorine end groups
(M.sub.n=3600, D=1.23 (PSt standards, THF line); M.sub.n=4100,
D=1.15 (PMMA standards, THF line); M.sub.n=6500, D=1.15 (PMMA
standards, DMF line)) was used to initiate DMAA polymerization in
order to prepare block copolymers. The target M.sub.n for the DMAA
block was always 10K, the reaction was run at room temperature, and
toluene was the solvent. The ratio Cl/CuCl/Me.sub.6Tren was 1/1/1.
The results are shown in Table 45. Because the DMF system of the
GPC has been broken for more than 8 weeks, I don't have all
M.sub.ns and polydispersities.
47TABLE 45 Preparation of polyDMMA-polyMA block copolymers.
DMAA/toluene Time Conv. Exp. v/v h % M.sub.n M.sub.w/M.sub.n
MA-DMAA1 1/3 45 8200 1.14 MA-DMAA2 1/3 15 7 8000 1.11 MA-DMAA3 1/5
21.83 18.6
[0454] The working procedure was slightly different.
MA-DMAA1:polyMA+CuCl were loaded in a Schlenk flask and cycled 3
times between vacuum and nitrogen. Then degassed DMAA, degassed
chlorobenzene and degassed Me.sub.6Tren were added.
[0455] MA-DMAA2: a Schlenk flask loaded with CuCl was cycled
3.times. between vacuum and nitrogen. Separately, polyMA was loaded
into another flask and cycled 3.times. between vacuum and nitrogen.
Then, degassed toluene was added, and the solution was transferred
to the flask containing CuCl. Then, DMAA, Me.sub.6Tren,
chlorobenzene were added.
[0456] MA-DMAA3: toluene, polyMA, DMAA and CB were loaded in a
flask, and after polyMA dissolved, the solution was bubbled with
nitrogen for 30 min. Then the solution was transferred into another
flask containing CuCl under nitrogen. Then, degassed Me.sub.6Tren
was added.
[0457] The GPC traces for the MA-DMAAI experiment showed a nice
shift of the molecular weight, which indicates that initiation
occurred.
EXAMPLE 46
Examination of Different Ligands
[0458] By replacing Me.sub.6TREN by TPMA (tripodal ligand with
pyridine groups), the conversion was much lower (Table 46). After
22 h the color of both reaction mixtures was green, characteristic
for Cu(II). Therefore, deactivation of the catalyst occurred.
48TABLE 46 DMAA polymerization with TPMA as a ligand Conversion
Exp. Initiating system % M.sub.n M.sub.w/M.sub.n DMAA103-1
MCP/CuCl/tpma 7.3 DMAA103-2 MBP/CuBr/tpma 6.3 Target M.sub.n = 10K;
DMAA/toluene = 1/3 v/v; Time = 22.16 h; RT.
EXAMPLE 47
Substituents on Amine Ligands for Control of Catalyst
Solubility/Reactivity
[0459] ATRP of styrene, MA and MMA were performed to evaluate the
application of a new ligand prepared to examine the effect of
different polarity substituents on amine ligands. Results are shown
in the following table. For comparison, results using a
structurally similar ligand are also shown. Preliminary one-point
results show the substituted linear triamine afforded controlled
polymerization only for MMA. For styrene or MA, experimental M, was
close to the calculated value; however, M.sub.w/M.sub.n was quite
high. Both substituted ligands yielded similar results. Apparently,
the unfavorable steric hindrance around the catalytic center can
affect the control of the polymerizations. It is interesting to
note that ligand A made from Michael addition did not lead to
soluble copper catalyst under the reaction conditions. In contrast,
the simple alkyl-substituted ligand B resulted in a homogenous
catalyst. 20
49TABLE 47 Effect of substituents on amine ligands temp time conv
Ligand monomer M.sub.tX (.degree. C.) (h) (%) M.sub.n,Cal
M.sub.n,SEC M.sub.w/M.sub.n A styrene.sup.a CuBr 90 17.5 62 6 200 9
400 2.75 A MA.sup.b CuBr 90 2.6 65 13 000 14 200 1.95 A MMA.sup.c
CuBr 90 4.1 71 14 200 13 000 1.40 B styrene CuBr 110 1.5 75 7 500 8
500 1.92 B MA CuBr 90 2.0 63 12 600 14 600 1.54 B MMA.sup.d CuBr 90
1.5 80 16 000 17 200 1.28 .sup.abulk; [styrene].sub.o/[PEBr].sub.o
= 96; [PEBr].sub.o/[CuBr].sub.o/[ligand].sub.o = 1/1/1. .sup.bbulk;
[MA].sub.o/[EBP].sub.o = 232;
[MBP].sub.o/[CuBr].sub.o/[ligand].sub.o = 1/1/1. .sup.c50 vol % in
anisole; [MMA].sub.o/[EBIB].sub.o = 200;
[EBIB].sub.o/[CuBr].sub.o/[ligand].sub.o = 1/1/1. .sup.d50 vol % in
anisole; [MMA].sub.o/[BPN].sub.o = 200;
[BPN].sub.o/[CuBr].sub.o/[liga- nd].sub.o = 1/0.5/0.5.
EXAMPLE 48
Polymerization from Surfaces
[0460] Materials. Trichlorosilane was obtained from Gelest.
10-Undecen-1-ol and 2-bromoisobutyryl bromide were obtained from
Aldrich. Styrene was distilled from calcium hydride. Methyl
acrylate was washed three times with 5% sodium hydroxide solution
and once with water. After drying with magnesium sulfate, the
monomer was obtained in pure form by distillation twice from
calcium chloride. 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,-
10,10-Heptadecafluorodecyl acrylate (fluoro acrylate) was distilled
at 90.degree. C. and 4 mmHg. All of these monomers were stored in
the drybox freezer immediately following distillation. tert-Butyl
acrylate was purified in the same manner as methyl acrylate but was
distilled only once from calcium chloride. The monomer was stored
in the freezer outside of the drybox. Karstedt's catalyst was
synthesized according to the method of Lewis et al. Copper-(I)
bromide (CuBr) was stirred in glacial acetic acid overnight,
filtered, and washed with absolute ethanol under an argon blanket.
The compound was dried under vacuum at 60.degree. C. overnight.
(PMDETA) was distilled from calcium hydride and stored at room
temperature in the drybox. The complex copper(II) bromide
bis-(4,4'-di-n-nonyl-2,2'-bipyridine) was prepared by stirring 0.25
g (1.1 mmol) of CuBr2 and 0.92 g (2.2 mmol) of dnNbpy in a 1:1 (v)
mixture of THF and acetonitrile at room temperature until a
homogeneous green solution formed. The solvents were removed by
trap-to-trap distillation, and the green solid dried under vacuum
(1 mmHg) overnight at room temperature. The complex copper(II)
bromide-N,N,N',N",N"-pentamethyldieth- ylenetriamine was prepared
by stirring 0.52 g (2.4 mmol) of CuBr2 and 0.41 g (2.4 mmol) of
PMDETA in methanol at room temperature until a homogeneous green
solution formed. The solvents were removed by trap-to-trap
distillation, and the green solid dried under vacuum (1 mmHg)
overnight at room temperature. Both compounds were henceforth
stored in the drybox. Chloroform was distilled from calcium hydride
and stored in the drybox. "Triple distillation" quality water for
contact angle measurements was obtained from a Barnstead Nanopure
II purification system.
[0461] Measurement. Film thickness was measured with a Gaertner
model L116B ellipsometer operating with a 633 nm He/Ne laser at a
70.degree. incident angle. The following refractive indices were
used for the various layers: 3.865 for native silicon, 1.465 for
silicon oxide, 1.527 for poly(acrylic acid), 1.466 for
poly(tert-butyl acrylate) (value from poly(n-butyl acrylate)),
1.339 for poly(fluoro acrylate), 1.5672 for poly-(methyl acrylate),
and 1.59 for polystyrene. Measurements were obtained at three spots
on each wafer, 10 measurements per spot. The surface composition
was measured using X-ray photoelectron spectroscopy (XPS) at 10-9
mmHg from a VG-Scientific Mg-KR X-ray source (h) 12 535.6 eV). The
energies of emitted electrons were measured using a Fissions Clam
II hemispherical analyzer at a pass energy of 50 eV. IR spectra of
the polymer films grown on silicon substrates were measured in the
external reflection mode using a Mattson RS1 FT-IR spectrometer
coupled with a custom-made reflection optical system. P-polarized
light was used at an incident angle of 80.degree. with respect to
the surface normal. A total of 1024 scans were co-added for each
spectrum at 4 cm -1 spectral resolution from both the sample and a
clean silicon reference. Contact angle measurements using both the
horizontal and tilting platform methods were obtained from a
Panasonic GP-KR222 video camera connected to a Hitachi video copy
processor model P71U. Angles from three different spots on each
wafer were measured 10 times and statistically compiled. Molecular
weights for free soluble polymers were measured in THF using a
Waters 510 liquid chromatograph pump equipped with four Polymer
Standards Service (PSS) columns (100 .ANG., 1000 .ANG., linear, and
guard) in series with a Waters 410 differential refractometer.
Molecular weights were calculated with PSS software; calibration
was based on low-polydispersity polystyrene standards. Prior to
injection, samples dissolved in either THF or chloroform were
passed through a 2 cm column of alumina followed by a 0.2 m syringe
filter. When an air/moisture-free environment was required, a
Vacuum Atmospheres HE-33 drybox was used. The concentrations of
oxygen and water were both below 1 ppm in the nitrogen
atmosphere.
EXAMPLE 48a
Initiator Synthesis and Monolayer Self-Assembly. 10-Undecen-1-yl
2-Bromo-2-methylpropionate
[0462] To a solution of 4.257 g (25 mmol) of a)-undecylenyl alcohol
in 25 mL of dry tetrahydrofuran was added 2.1 mL of pyridine (26.5
mmol) followed by dropwise addition of 3.10 mL of 2-bromoisobutyryl
bromide (25 mmol) over 5 min. The mixture was stirred at room
temperature overnight and then diluted with hexane (50 mL) and
washed with 2 N HCl and twice with water. The organic phase was
dried over sodium sulfate and filtered. The solvent was removed
from the filtrate under reduced pressure, and the colorless oily
residue was purified by flash column chromatography (hexane/ethyl
acetate 25/1 v/v) to give 7.34 g (92%) of the ester as a colorless
oil.
[0463] (11-(2-Bromo-2-methyl)propionyloxy)undecyltrichloro-silane.
To a dry flask were added 1.35 g (4.23 mmol) of 10-undecen-1-yl
2-bromo-2-methylpropionate and 4.2 mL of trichlo-rosilane (42.6
mmol), followed by the addition of Karstedt catalyst (4 L, 100 ppm
Pt equivalents). The mixture was stirred at room temperature while
the reaction was monitored by GC. The reaction was usually complete
within 5 h. The solution was quickly filtered through a plug of
silica gel to remove the catalyst. The excess reagent was removed
under reduced pressure. The residue was found to be >95% pure by
GC and was used as such. The compound can be further purified by
vacuum distillation. When not in use, the compound was stored in
the drybox at 5.degree. C.
[0464] Silicon (100) wafers, cut into 1 cm 2 pieces, were cleaned
in a toluene bath under ultrasound for 5 min. The wafers were then
rinsed with HPLC grade toluene, acetone, and absolute (water-free)
ethanol and dried in a nitrogen stream. The samples were then
oxidized in a UV/ozone chamber for 15 min; the thickness of the
SiO2 layer was 16.1 .ANG. measured by ellipsometry. The wafers were
transferred to the drybox and placed into a solution of 5 L of the
trichlorosilane in 10 mL of toluene (4 mM on wafer). The samples
were allowed to stand in this solution for 18 h without stirring.
The wafers were removed from the solution, cleaned by ultrasound in
toluene for 1 min, rinsed again with toluene, acetone, and absolute
ethanol, and again dried in a nitrogen stream. When not used in
reactions, the wafers were stored at room temperature in the
drybox.
EXAMPLES 48b
Polymerizations from Surfaces
[0465] For polymerizations where samples were removed from a common
reaction medium as a function of time, experiments were performed
in glass jars with screw-top lids in a thermostated oil bath in the
drybox. The purpose was to allow easy removal of individual wafers
without prolonged exposure of the reaction to oxygen. A
representative example is as follows: 4.5 g (43 mmol) of styrene
and 36 mg (3.4.times.10-2 mmol) of CuBr2(dnNbpy)2 were placed into
the reactor and stirred until a homogeneous purple solution formed.
Then, 99 mg (0.69 mmol) of CuBr, 560 mg (1.4 mmol) of dnNbpy, and
2.7 g (26 mmol) of styrene were added and stirred until a
homogeneous maroon solution formed. The wafers were then placed
into the reactor, and the covered apparatus was held in a
100.degree. C. oil bath. Periodically, wafers were removed from the
reactor and rinsed with chloroform. At the conclusion of the
reaction, any adsorbed polymer formed adventitiously in solution
was removed from the wafers by Soxhlet extraction in toluene for
24-48 h. Upon removal from the extractor, the wafers were dried
under a stream of argon or nitrogen and stored at room temperature
under air. For experiments examining the corresponding molecular
weights of chains grown in solution, the above procedure was
duplicated with the exception that, after all reagents had combined
and homogeneity reached, 11 L (7.3-10-2 mmol) of ethyl
2-bromoisobutyrate was added in the absence of wafers. The reaction
was conducted in such a way that solution samples were removed at
times corresponding to removal of the wafers The molecular weight
of the polymer samples dissolved in THF was then determined. When a
polymerization from only one wafer was performed, a different
procedure was adopted. Into a 10 mL round-bottom flask was placed
3.0 mg (1.3.sub.--10-2 mmol) of CuBr2,49 mg (0.34 mmol) of CuBr,
and 290 mg (0.71 mmol) of dnNbpy. The solids were degassed under
room-temperature vacuum for 20 min and backfilled with nitrogen. To
this, 4.4 g (34 mmol) of tert-butyl acrylate, which was
deoxygenated by a nitrogen bubble for 20 min, was added, and the
mixture was stirred in a 60.degree. C. oil bath under nitrogen for
30 min to promote formation of a homogeneous maroon solution.
During the above process, a silicon wafer, with a preformed
polystyrene layer, was placed into a 25 mL sidearm Erlenmeyer
flask, covered with a rubber septum, and connected to the Schlenk
line via rubber vacuum tubing. The flask was evacuated for 15 min
and backfilled with nitrogen. The monomer/catalyst solution was
then cannula transferred into the Erlenmeyer flask, and the reactor
was placed into a 90.degree. C. oil bath and stirred under
nitrogen. After 4.5 h the wafer was removed from the flask and
rinsed with chloroform. The wafer was then Soxhlet extracted with
toluene for 20 h and dried under a nitrogen stream.
[0466] The "persistent radical effect," applied to controlled
radical polymerizations, suggests that a sufficient concentration
of deactivator be present to provide reversible deactivation of
chains during propagation. In a typical ATRP process, a few percent
of chains terminate and spontaneously form deactivating Cu(II)
species. As detected by EPR, the concentration of Cu(II) is in the
range 10-3 mol/L, and such a concentration is needed for a
sufficiently controlled process. In the previous controlled radical
polymerization experiments growing dense polymer films from the
surface, the "sacrificial" initiator was present in solution. The
"free" (untethered) chains terminated in solution, thereby
spontaneously forming a sufficient amount of the deactivator. It
was reported that the presence of the sacrificial initiator was
required for polymerization control. In our experiments, we did not
use the sacrificial initiator but added a sufficient amount of the
deactivator at the beginning of the reaction. Otherwise, no control
can be observed, and the process would resemble a redox-initiated
conventional radical system. Since under typical conditions of
self-assembly the concentration of initiator is such that even the
termination of all alkyl halide fragments would provide a
concentration of CuBr2 that is 10 000 times lower than that
observed and required for a well-controlled ATRP. This was resolved
by the addition of the persistent radical prior to the commencement
of the reaction.
[0467] Bulk ATRP of methyl acrylate from the same
2-bromoisobutyrate-modif- ied silicon wafers. The ligand in the
transition-metal complex was PMDETA. 1 mol % CuBr and 0.03% CuBr2
both relative to monomer were used; the deactivator concentration
was again determined from EPR measurements. It was found that even
after stirring in monomer for 30 min at 70.degree. C., the
CuBr2(PMDETA) complex was not entirely soluble. However, a linear
increase in film thickness with time indicated that there was
sufficient deactivator in solution to provide control over the
growth of the brush chains.
EXAMPLE 48c
Block Copolymers
[0468] An additional method toward verifying the functionality of a
polymer prepared by ATRP is its use as a macroinitiator for the
ATRP of the same or another monomer. Since XPS was not conclusive
in determining the concentration of bromine, a chain extension of
methyl acrylate from a surface composed of a polystyrene layer was
performed. The polymerization was initiated from a 10 nm thick
macro-initiator layer using 1 mol % CuBr(dnNbpy)2 and 0.03 mol %
CuBr2(dnNbpy)2 dissolved in the bulk monomer. Similar to
polymerizations from the initiator bound to the surface, show that
a linear relationship was established between the increase in layer
thickness and reaction time. The increase in thickness upon
addition of the second block demonstrated that some fraction of the
chains contained terminal bromine groups capable of participating
in ATRP. Similar to the polystyrene-modified surfaces prepared by
redox initiated polymerization, the final sample, more than 100 nm
thick, had a blue appearance.
[0469] In another example, a 26 nm thick polystyrene layer was
grown from two silicon wafers primed with initiator. One of those
substrates was then chain extended with tert-butyl acrylate using
1% CuBr(dnN-bpy) 2 and 0.03% CuBr2(dnNbpy)2 at 90.degree. C. An
increase in film thickness to 37 nm was measured by ellipsometry
after a 4.5 h reaction time.
EXAMPLE 48d
Tuning Surface Properties
[0470] A benefit of radical polymerization over other techniques
such as ionic or metathesis processes is the wide variety of
monomers amenable to the process. Therefore, by choice of monomer
one can tune the physical properties of the surface. One such
property is hydrophilicity. The water contact angles of a series of
polymers prepared by ATRP from identically modified silicon wafers
was measured. A polystyrene layer 10 nm thick showed a contact
angle of 90.degree.. When that surface was chain extended with an
additional 12 nm of poly(tert-butyl acrylate), the surface became
slightly less hydrophilic (86.degree.). The polyacrylate was then
hydrolyzed to poly-(acrylic acid) by refluxing a solution of 10%
aqueous HCl over the wafer overnight. Ellipsometry showed that the
thickness decreased to 16 nm most likely due to relaxation of the
chains upon removal of the bulky tert-butyl groups. The presence of
the acid was confirmed by the significant decrease of the water
contact angle from 86.degree. to 18.degree..
[0471] Finally, in a separate experiment a very hydrophobic surface
composed of a poly(fluoro acrylate) was constructed. The large
contact angle of 119.degree. is typical of surfaces containing high
fluorine contents. All of the above examples demonstrate the
versatility of the ATRP technique to polymerize a variety of
monomers from the surfaces and the continued activity of the
terminus of the tethered polymer towards further controlled
polymerization. This terminal functionality remains until the end
groups are deliberately transformed into another group.
EXAMPLE 49
MMA Polymerization with Ni and Mn and Onium Salts
[0472] a) Nickel
[0473] MMA polymerization with NiBr.sub.2 and tetrabutylphosphonium
bromide (TBPB) at 80.degree. C., in xylene solution (MMA/xylene=1/1
v/v), target M.sub.n=30K was carried out. The results are displayed
in Table 48.
50TABLE 48 MMA polymerization with the system ethyl
2-bromoisobutyrate (EBIB)/NiBr.sub.2/TBPB Conv Exp. NIBr.sub.2/TBPB
(%) M.sub.n,th M.sub.n M.sub.w/M.sub.n NM1-1 1/0.5 16.2 4860 36000
3.63 2 1/1 13.3 3990 29000 4.05 3 1/1.5 11.4 3420 30600 4.84 4 1/2
10.5 3150 30300 4.44 5 1/2.5 14.9 4470 36000 4.02 6 1/3 15.8 4740
40000 3.79 Exp. cond: EBIB/NiBr.sub.2 = 1/1; time = 2.5 hr
[0474] The samples were heterogeneous at both RT and 80.degree. C.
A blue precipitate formed after 15 min at 80.degree. C. in samples
2-6.
[0475] b) Manganese
[0476] Similar conditions as for nickel were employed. The results
are displayed in Table 49.
51TABLE 49 MMA polymerization with the system EBIB/MnX.sub.2/onium
salts Time Conv Exp. Catalytic system hr (%) M.sub.n,th M.sub.n
M.sub.w/M.sub.n MM1-1 MnCl.sub.2/TBAC 2.33 13.3 39300 33650 2.74
1/0.5 2 MnCl.sub.2 " 25.1 7530 65500 3.38 1/1 3 MnCl.sub.2 " 21.0
6300 58400 4.21 1/1.5 4 MnCl.sub.2 " 39.6 11880 88100 2.23 1/2 5
MnCl.sub.2 " 44.3 13290 95300 2.07 1/2.5 6 MnCl.sub.2 " 17.7 5310
49400 8.43 1/3 MM3-1 MnBr.sub.2/TBPB 5 4.5 1350 12800 4.65 1/0.5 2
MnBr.sub.2/TBPB " 9.5 2850 21360 3.56 1/1 3 MnBr.sub.2/TBPB " 17.4
5220 42540 2.60 1/1.5 4 MnBr.sub.2/TBPB " 19.2 5760 57700 5.19 1/2
5 MnBr.sub.2/TBPB " 16.6 4980 57000 6.78 1/2.5 6 MnBr.sub.2/TBPB "
28.6 8580 68320 4.09 1/3 MM4-1 Mn(OAc).sub.2/TBPB 2.5 25.3 7590
37100 6.71 1/0.5 2 Mn(OAc).sub.2/TBPB " 18.2 5460 49100 5.58 1/1 3
Mn(OAc).sub.2/TBPB " 15.2 4560 46000 4.94 1/1.5 4
Mn(OAc).sub.2/TBPB " 16.5 4950 44600 5.52 1/2 5 Mn(OAc).sub.2/TBPB
" 18.3 5490 49200 4.98 1/2.5 6 Mn(OAc).sub.2/TBPB " 22.4 6720 55400
6.06 1/3 Exp. cond: EBIB/MnX.sub.2 = 1/1, TBAC = tetrabutylammonium
chloride, TBAB = tetrabutylammonium bromide
[0477] By plotting M.sub.n versus conversion for the system
MnCl.sub.2/TBAC an increase in molecular weight with conversion was
noticed (FIG. 18).
[0478] c) Chromium
[0479] Experiments using CrCl.sub.2 as metal in conjunction with
tetrabutylammonium chloride in the MMA polymerization was
performed. The results are shown in Table 50.
52TABLE 50 MMA polymerization with CrCl.sub.2/TBAC Exp.
CrCl.sub.2/TBAC Conversion % M.sub.n M.sub.w/M.sub.n ChM1-1 1/0.5 8
40300 5.68 1-2 1/1 8 64000 9.52 1-3 1/1.5 4 61500 6.54 1-4 1/2 4.5
61700 4.63 1-5 1/2.5 2.5 74500 5.91 1-6 1/3 2.5 12480 12.8 Exp.
cond.: 80.degree. C.; MMA/o-xylene = 1/1 v/v; target M.sub.n = 30
K; EBIB/CrCl.sub.2 = 1/1.
* * * * *