U.S. patent application number 09/862240 was filed with the patent office on 2002-05-23 for heterocycle containing control agents for living-type free radical polymerization.
Invention is credited to Chang, Han Ting, Charmot, Dominique.
Application Number | 20020061990 09/862240 |
Document ID | / |
Family ID | 25338014 |
Filed Date | 2002-05-23 |
United States Patent
Application |
20020061990 |
Kind Code |
A1 |
Charmot, Dominique ; et
al. |
May 23, 2002 |
Heterocycle containing control agents for living-type free radical
polymerization
Abstract
Control agents that have a nitrogen-nitrogen bond in a cyclic
ring covalently bonded to a thiocarbonyl moiety are provided for
living-type free radical polymerization without a bimodal molecular
weight distribution at high monomer conversions. These control
agents provide superior properties for the production of block
polymers having narrow molecular weight distributions.
Inventors: |
Charmot, Dominique; (Palo
Alto, CA) ; Chang, Han Ting; (Fremont, CA) |
Correspondence
Address: |
SYMYX TECHNOLOGIES INC
LEGAL DEPARTMENT
3100 CENTRAL EXPRESS
SANTA CLARA
CA
95051
|
Family ID: |
25338014 |
Appl. No.: |
09/862240 |
Filed: |
May 22, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09862240 |
May 22, 2001 |
|
|
|
09676267 |
Sep 28, 2000 |
|
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Current U.S.
Class: |
526/205 |
Current CPC
Class: |
C08F 2/38 20130101 |
Class at
Publication: |
526/205 |
International
Class: |
C08F 002/00; C08F
004/00 |
Claims
What is claimed is:
1. A method comprising (1) forming a mixture of one or more
monomers, at least one free radical source and a control agent
characterized by the general formula: 10wherein R.sup.1 is any
group that can be expelled as its free radical form in an
addition-fragmentation reaction and each of R.sup.2, R.sup.3 and
R.sup.4 is independently selected from the group consisting of
hydride, optionally substituted hydrocarbyl and
heteroatom-containing hydrocarbyl; (2) subjecting said mixture to
polymerization conditions to achieve a conversion of said monomers
of at least 70%; and (3) recovering a polymer having a molecular
weight distribution below or equal to 1.10.
2. The method of claim 1, wherein an initiator is the source of
free radicals.
3. The method of claim 1, wherein the polymer has a degree of
polymerization of at least about 200.
4. The method of claim 1, wherein R.sup.1 is selected from the
group consisting of optionally substituted alkyl, optionally
substituted aryl, optionally substituted alkenyl, optionally
substituted alkoxy, optionally substituted heterocyclyl, optionally
substituted alkylthio, optionally substituted amino and optionally
substituted polymer chains.
5. The method of claim 4, wherein R.sup.1 is selected from the
group consisting of --CH.sub.2Ph,
--CH(CH.sub.3)CO.sub.2CH.sub.2CH.sub.3,
--CH(CO.sub.2CH.sub.2CH.sub.3).sub.2, --C(CH.sub.3).sub.2CN,
--CH(Ph)CN, --CH(CH.sub.3)Ph and --C(CH.sub.3).sub.2Ph.
6. The method of claim 1, wherein said polymerization conditions
comprise a temperature in the range of from about 20.degree. C. to
about 110.degree. C.
7. The method of claim 1, further wherein two or more monomers are
added to said polymerization mixture and said two or more monomers
are added sequentially or simultaneously.
8. The method of claim 1, wherein said polymerization conditions
comprise living kinetics.
9. The method of claim 1, wherein said polymer has a mono-modal
molecular weight distribution.
10. A polymer formed by the method of any of claims 1, 2 or 3.
11. The polymer of claim 9, wherein said copolymer is a block
copolymer.
12. A method comprising (1) forming a mixture of one or more
monomers, at least one free radical source and a control agent
characterized by the general formula: 11wherein R.sup.1 is any
group that can be expelled as its free radical form in an
addition-fragmentation reaction and each of R.sup.2, R.sup.3 and
R.sup.4 is independently selected from the group consisting of
hydride, optionally substituted hydrocarbyl and
heteroatom-containing hydrocarbyl; (2) subjecting said mixture to
polymerization conditions to achieve a conversion of said monomers
of at least 70%; and (3) recovering a polymer having a molecular
weight distribution below or equal to 1.10.
13. The method of claim 12, wherein the polymer has a degree of
polymerization of at least about 200.
14. The method of claim 12, wherein R.sup.1 is selected from the
group consisting of optionally substituted alkyl, optionally
substituted aryl, optionally substituted alkenyl, optionally
substituted alkoxy, optionally substituted heterocyclyl, optionally
substituted alkylthio, optionally substituted amino and optionally
substituted polymer chains.
15. The method of claim 12, wherein said polymerization conditions
comprise a temperature in the range of from about 20.degree. C. to
about 110.degree. C.
16. The method of claim 12, further wherein two or more monomers
are added to said polymerization mixture and said two or more
monomers are added sequentially or simultaneously.
17. The method of claim 12, wherein said polymerization conditions
comprise living kinetics.
18. The method of claim 12, wherein said polymer has a mono-modal
molecular weight distribution.
19. A polymer formed by the method of any of claims 12, 13 or
14.
20. The polymer of claim 19, wherein said copolymer is a block
copolymer.
Description
[0001] This application is a continuation in part of pending U.S.
patent application Ser. No. 09/676,267, filed Sep. 28, 2000, which
is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to new compounds useful in
assisting in the polymerization of monomers in a free radical
polymerization that has living-type kinetics. Polymers made with
the control agents and processes for polymerization are also
included.
BACKGROUND OF THE INVENTION
[0003] The use and mechanism of control agents for free radical
polymerization is now generally known, see for example U.S. Pat.
No. 6,153,705, WO98/01478, WO99/35177, WO99/31144, and WO98/58974,
each of which is incorporated herein by reference. The compounds
described in these references are generally referred to as chain
transfer agents. These references generally disclose
dithiocarbamate or xanthate control agents having heterocyclical
moieties. See, for example, WO 99/31144 at pages 31-34.
[0004] One general problem is that at high monomer conversions
(e.g., above 70%) the polymers made with these control agents have
a very high molecular weight component, which leads to a polymer
that generally does not have a mono-modal molecular weight
distribution. Without wishing to be bound by any particular theory,
it is believed that this high molecular weight component is created
at high conversions due to the coupling of propagating polymer
chains. This coupling creates chain ends that cannot continue to be
polymerized and are effectively "dead" toward further propagation.
The presence of "dead" chain is particularly troubling when forming
block copolymers with this controlled free radical polymerization
methodology because a typical procedure for block formation uses
the sequential addition of different monomers. "Dead" chains cannot
participate in block formation in this methodology. Thus, there is
a desire to eliminate the formation of dead chains.
[0005] With some embodiments, gel permeation chromatography
experiments reveal a bimodal molecular weight distribution of the
polymers made with free radical polymerization chain transfer
agents of the type disclosed in these references. For example, WO
99/31144 fails to distinguish between bimodal molecular weight
distributions and those that may be otherwise; consider example 22,
where a bimodal distribution is revealed for control agent (62).
The implication from a bimodal molecular weight distribution is
that a number of dead polymer chains exist in those polymer
samples.
[0006] It has now been found that certain control agents eliminate
the bimodal molecular weight distribution at high conversions,
additionally providing a very narrow molecular weight distribution.
These control agents are particularly useful for block polymer
formation using a sequential addition of monomer methodology.
SUMMARY OF THE INVENTION
[0007] This invention provides control agents that effectively
diminishes or eliminates a bimodal molecular weight distribution at
monomer conversions greater than 70%. These control agents also
provide a polymer with a very narrow molecular weight distribution,
generally less than about 1.10. In general the control agents
useful to create the polymers of this invention and useful in the
processes of this invention may be represented by the following
general formula: 1
[0008] wherein R.sup.1 may be selected from the group consisting of
optionally substituted hydrocarbyl and heteroatom-containing
hydrocarbyl and each of R.sup.2, R.sup.3 and R.sup.4 is
independently selected from the group consisting of hydride,
optionally substituted hydrocarbyl and heteroatom-containing
hydrocarbyl.
[0009] Other aspects of this invention include polymerization
processes using these control agents and polymers that can be made
with the control agents. In particular, the control agents of this
invention provide living-type kinetics and as such allow for the
preparation of desired products, including block polymers, star
architectures, grafts and hyperbranched polymers.
[0010] Thus, it is an object of this invention to provide control
agents for a living-type free radical polymerization process where
the polymers made during the process do not have a bimodal
molecular weight distribution at monomer conversions greater than
about 70%.
[0011] It is another object of this invention to provide a system
for free radical polymerization of monomers that employs
living-type kinetics where the molecular weight distribution is
less than about 1. 10.
[0012] Further aspects and objects of this invention will be
evident to those of skill in the art upon review of this
specification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a trace from the gel permeation chromatography
experiment for the polymer obtained from run 1 of Example 2.
[0014] FIG. 2 is a trace from the gel permeation chromatography
experiment for the polymer obtained from run 2 of Example 2.
[0015] FIG. 3 is a trace from the gel permeation chromatography
experiment for the polymer obtained from run 3 of Example 2.
[0016] FIG. 4 is a trace from the gel permeation chromatography
experiment for the polymer obtained from run 4 of Example 2.
[0017] FIG. 5 is a trace from the gel permeation chromatography
experiment for the polymer obtained from run 5 of Example 2.
[0018] FIG. 6 is a trace from the gel permeation chromatography
experiment for the polymer obtained from run 6 of Example 2.
DETAILED DESCRIPTION OF THE INVENTION
[0019] This invention generally relates to the use of a specific
class of free radical control agents that produce polymers having
very narrow molecular weight distributions at high conversions.
These polymers may also have a high degree of polymerization (or
molecular weight), depending on the application.
[0020] In describing and claiming the present invention, the
following terminology will be used in accordance with the
definitions set out below. A named R group will generally have the
structure that is recognized in the art as corresponding to R
groups having that name. For the purposes of illustration,
representative R groups as enumerated above are defined herein.
These definitions are intended to supplement and illustrate, not
preclude, the definitions known to those of skill in the art.
[0021] It is also to be understood that the terminology used herein
is for the purpose of describing particular embodiments only, and
is not intended to be limiting. As used in this specification and
the appended claims, the singular forms "a," "an" and "the" include
plural referents unless the context clearly dictates otherwise. In
describing and claiming the present invention, the following
terminology will be used in accordance with the definitions set out
below.
[0022] The following definitions pertain to chemical structures,
molecular segments and substituents:
[0023] As used herein, the phrase "having the structure" is not
intended to be limiting and is used in the same way that the term
"comprising" is commonly used. The term "independently selected
from the group consisting of" is used herein to indicate that the
recited elements, e.g., R groups or the like, can be identical or
different (e.g., R.sup.2 and R.sup.3 in the structure of formula
(1) may all be substituted alkyl groups, or R.sup.2 may be hydrido
and R.sup.3 may be methyl, etc.).
[0024] "Optional" or "optionally" means that the subsequently
described event or circumstance may or may not occur, and that the
description includes instances where said event or circumstance
occurs and instances where it does not. For example, the phrase
"optionally substituted hydrocarbyl" means that a hydrocarbyl
moiety may or may not be substituted and that the description
includes both unsubstituted hydrocarbyl and hydrocarbyl where there
is substitution.
[0025] The term "alkyl" as used herein refers to a branched or
unbranched saturated hydrocarbon group typically although not
necessarily containing 1 to about 24 carbon atoms, such as methyl,
ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, octyl,
decyl, and the like, as well as cycloalkyl groups such as
cyclopentyl, cyclohexyl and the like. Generally, although again not
necessarily, alkyl groups herein contain 1 to about 12 carbon
atoms. The term "lower alkyl" intends an alkyl group of one to six
carbon atoms, preferably one to four carbon atoms. "Substituted
alkyl" refers to alkyl substituted with one or more substituent
groups, and the terms "heteroatom-containing alkyl" and
"heteroalkyl" refer to alkyl in which at least one carbon atom is
replaced with a heteroatom.
[0026] The term "alkenyl" as used herein refers to a branched or
unbranched hydrocarbon group typically although not necessarily
containing 2 to about 24 carbon atoms and at least one double bond,
such as ethenyl, n-propenyl, isopropenyl, n-butenyl, isobutenyl,
octenyl, decenyl, and the like. Generally, although again not
necessarily, alkenyl groups herein contain 2 to about 12 carbon
atoms. The term "lower alkenyl" intends an alkenyl group of two to
six carbon atoms, preferably two to four carbon atoms. "Substituted
alkenyl" refers to alkenyl substituted with one or more substituent
groups, and the terms "heteroatom-containing alkenyl" and
"heteroalkenyl" refer to alkenyl in which at least one carbon atom
is replaced with a heteroatom.
[0027] The term "alkynyl" as used herein refers to a branched or
unbranched hydrocarbon group typically although not necessarily
containing 2 to about 24 carbon atoms and at least one triple bond,
such as ethynyl, n-propynyl, isopropynyl, n-butynyl, isobutynyl,
octynyl, decynyl, and the like. Generally, although again not
necessarily, alkynyl groups herein contain 2 to about 12 carbon
atoms. The term "lower alkynyl" intends an alkynyl group of two to
six carbon atoms, preferably three or four carbon atoms.
"Substituted alkynyl" refers to alkynyl substituted with one or
more substituent groups, and the terms "heteroatom-containing
alkynyl" and "heteroalkynyl" refer to alkynyl in which at least one
carbon atom is replaced with a heteroatom.
[0028] The term "alkoxy" as used herein intends an alkyl group
bound through a single, terminal ether linkage; that is, an
"alkoxy" group may be represented as --O-- alkyl where alkyl is as
defined above. A "lower alkoxy" group intends an alkoxy group
containing one to six, more preferably one to four, carbon atoms.
The term "aryloxy" is used in a similar fashion, with aryl as
defined below.
[0029] The term "aryl" as used herein, and unless otherwise
specified, refers to an aromatic substituent containing a single
aromatic ring or multiple aromatic rings that are fused together,
linked covalently, or linked to a common group such as a methylene
or ethylene moiety. The common linking group may also be a carbonyl
as in benzophenone, an oxygen atom as in diphenylether, or a
nitrogen atom as in diphenylamine. Preferred aryl groups contain
one aromatic ring or two fused or linked aromatic rings, e.g.,
phenyl, naphthyl, biphenyl, diphenylether, diphenylamine,
benzophenone, and the like. In particular embodiments, aryl
substituents have 1 to about 200 carbon atoms, typically 1 to about
50 carbon atoms, and preferably 1 to about 20 carbon atoms.
"Substituted aryl" refers to an aryl moiety substituted with one or
more substituent groups, (e.g., tolyl, mesityl and perfluorophenyl)
and the terms "heteroatom-containing aryl" and "heteroaryl" refer
to aryl in which at least one carbon atom is replaced with a
heteroatom.
[0030] The term "aralkyl" refers to an alkyl group with an aryl
substituent, and the term "aralkylene" refers to an alkylene group
with an aryl substituent; the term "alkaryl" refers to an aryl
group that has an alkyl substituent, and the term "alkarylene"
refers to an arylene group with an alkyl substituent.
[0031] The term "heteroatom-containing" as in a
"heteroatom-containing hydrocarbyl group" refers to a molecule or
molecular fragment in which one or more carbon atoms is replaced
with an atom other than carbon, e.g., nitrogen, oxygen, sulfur,
phosphorus or silicon. Similarly, the term "heteroalkyl" refers to
an alkyl substituent that is heteroatom-containing, the term
"heterocyclic" refers to a cyclic substituent that is
heteroatom-containing, the term "heteroaryl" refers to an aryl
substituent that is heteroatom-containing, and the like. When the
term "heteroatom-containing" appears prior to a list of possible
heteroatom-containing groups, it is intended that the term apply to
every member of that group. That is, the phrase
"heteroatom-containing alkyl, alkenyl and alkynyl" is to be
interpreted as "heteroatom-containing alkyl, heteroatom-containing
alkenyl and heteroatom-containing alkynyl."
[0032] "Hydrocarbyl" refers to univalent hydrocarbyl radicals
containing 1 to about 30 carbon atoms, preferably 1 to about 24
carbon atoms, most preferably 1 to about 12 carbon atoms, including
branched or unbranched, saturated or unsaturated species, such as
alkyl groups, alkenyl groups, aryl groups, and the like. The term
"lower hydrocarbyl" intends a hydrocarbyl group of one to six
carbon atoms, preferably one to four carbon atoms. "Substituted
hydrocarbyl" refers to hydrocarbyl substituted with one or more
substituent groups, and the terms "heteroatom-containing
hydrocarbyl" and "heterohydrocarbyl" refer to hydrocarbyl in which
at least one carbon atom is replaced with a heteroatom.
[0033] By "substituted" as in "substituted hydrocarbyl,"
"substituted aryl," "substituted alkyl," "substituted alkenyl" and
the like, as alluded to in some of the aforementioned definitions,
is meant that in the hydrocarbyl, hydrocarbylene, alkyl, alkenyl or
other moiety, at least one hydrogen atom bound to a carbon atom is
replaced with one or more substituents that are functional groups
such as hydroxyl, alkoxy, thio, phosphino, amino, halo, silyl, and
the like. When the term "substituted" appears prior to a list of
possible substituted groups, it is intended that the term apply to
every member of that group. That is, the phrase "substituted alkyl,
alkenyl and alkynyl" is to be interpreted as "substituted alkyl,
substituted alkenyl and substituted alkynyl." Similarly,
"optionally substituted alkyl, alkenyl and alkynyl", for example,
is to be interpreted as "optionally substituted alkyl, optionally
substituted alkenyl and optionally substituted alkynyl."
[0034] As used herein the term "silyl" refers to the
--SiZ.sup.1Z.sup.2Z.sup.3 radical, where each of Z.sup.1, Z.sup.2,
and Z.sup.3 is independently selected from the group consisting of
hydrido and optionally substituted alkyl, alkenyl, alkynyl, aryl,
aralkyl, alkaryl, heterocyclic, alkoxy, aryloxy and amino.
[0035] The term "amino" is used herein to refer to the group
--NZ.sup.1Z.sup.2, where each of Z.sup.1 and Z.sup.2 is
independently selected from the group consisting of hydrido and
optionally substituted alkyl, alkenyl, alkynyl, aryl, aralkyl,
alkaryl and heterocyclic.
[0036] As used herein all reference to the elements and groups of
the Periodic Table of the Elements is to the version of the table
published by the Handbook of Chemistry and Physics, CRC Press,
1995, which sets forth the new IUPAC system for numbering
groups.
[0037] This invention provides control agents useful for the
control of free radical polymerization reactions. In general a free
radical polymerization is carried out with these control agents by
creating a mixture of at least one polymerizable monomer, the
control agent and optionally at least one source of free radicals,
e.g., an initiator. The source of free radicals is optional because
some monomers may self-initiate upon heating. After or upon forming
the polymerization mixture, the mixture is subjected to
polymerization conditions. Polymerization conditions are those
conditions that cause the at least one monomer to form at least one
polymer, as discussed herein, such as temperature, pressure,
atmosphere, ratios of starting components used in the
polymerization mixture, reaction time or external stimuli of the
polymerization mixture.
[0038] Control Agents
[0039] Generally, the control agents useful in this invention may
be characterized by the formula: 2
[0040] wherein R.sup.1 is generally any group that can be easily
expelled under its free radical form (R.sup.1.circle-solid.) upon
an addition-fragmentation reaction, as depicted below in Scheme 1:
3
[0041] In Scheme 1, P.circle-solid. is a free radical, typically a
macro-radical, such as polymer chain. More specifically, R.sup.1 is
selected from the group consisting of optionally substituted
hydrocarbyl and heteroatom-containing hydrocarbyl. Even more
specifically, R.sup.1 is selected from the group consisting of
optionally substituted alkyl, aryl, alkenyl, alkoxy, heterocyclyl,
alkylthio, amino and polymer chains. And still more specifically,
R.sup.1 is selected from the group consisting of --CH.sub.2Ph,
--CH(CH.sub.3)CO.sub.2CH.sub.2CH.sub.3,
--CH(CO.sub.2CH.sub.2CH.sub.3).sub.2, --C(CH.sub.3).sub.2CN,
--CH(Ph)CN, --CH(CH.sub.3)Ph and --C(CH.sub.3).sub.2Ph.
[0042] Each of R.sup.2, R.sup.3 and R.sup.4 is independently
selected from the group consisting of hydride, optionally
substituted hydrocarbyl and heteroatom-containing hydrocarbyl. More
specifically, R.sup.2 may be selected from the group consisting of
hydride, optionally substituted alkyl aryl, alkenyl, alkynyl,
aralkyl, alkoxy, heterocyclyl, alkylthio, amino and optionally
substituted heteroatom-containing alkyl, aryl, alkenyl, alkynyl,
and aralkyl. In some embodiments, R.sup.2, R.sup.3 and/or R.sup.4
may be joined in a ring structure, with the ring having from 5 to
10 atoms in the backbone of the ring (including bicyclic, tricyclic
or high order ring structures). For example, R.sup.2 may be
combined with R.sup.3 and R.sup.3 may be combined with R.sup.4.
[0043] In other embodiments, a multifunctional control agent is
used. These embodiments allow for selection of certain polymer
architectures, such as stars. In these embodiments, the control
agents may be represented by the general formula: 4
[0044] where R.sup.1, R.sup.2, R.sup.3 and R.sup.4 each have the
above definitions, with the proviso that R.sup.1 is multifunctional
and j is 1-12, but more specifically 1-4. For example, R.sup.1 may
be heteroatom containing hydrocarbyl, with an alkyl or aryl at the
center, leading to structures such as: 5
[0045] The control agents of this invention are synthesized,
generally, by methods known to those of skill in the art. The
general synthetic approach comprises nitrogen nucleophilic addition
to carbon disulfide and subsequent alkylation of the resulting
dithiocarbazate with alkylhalides in a one-pot methodology, as
shown in the following scheme 2: 6
[0046] This method is similar to those published in scientific
journals, e.g., Castro et al., J Org. Chem., 1984, 49, 863, which
is incorporated herein by reference.
[0047] The synthesis conditions optimized for particular
nucleophiles--pyrazoles and their derivatives include: temperature
in the range of 0.degree. C. to ambient; solvents--alcohols,
acetone, acetonitrile, dioxane, dimethylformamide (DMF),
dimethylsulfoxide (DMSO); base--sodium hydroxide, potassium
hydroxide, and sodium hydride. The optimized conditions include
using sodium hydroxide as the base in DMSO at ambient temperature.
The general procedure comprises starting with the pyrazole or its
derivative dissolved in DMSO in approximately a 0.5-1.0 M
concentration at ambient temperature. The solution is then treated
with approximately 1 equivalent of NaOH and followed by addition of
approximately 1 equivalent of carbon disulfide. The resulting
solution is then stirred (for example, for approximately 1 hour at
ambient temperature) before addition of approximately 1 equivalent
of an alkylation agent. Work-up may comprise addition of water,
extraction with organic solvent, and drying. The desired control
agent may be purified by chromatography and/or re-crystallization
and may be characterized by .sup.1H NMR, .sup.13C NMR, and
GC/MS.
[0048] Polymerization Processes
[0049] The polymerization conditions that may be used include
temperatures for polymerization typically in the range of from
about 20.degree. C. to about 110.degree. C., more preferably in the
range of from about 50.degree. C. to about 90.degree. C. and even
more preferably in the range of from about 60.degree. C. to about
80.degree. C. The atmosphere may be controlled, with an inert
atmosphere being preferred, such as nitrogen or argon. The
molecular weight of the polymer is controlled via adjusting the
ratio of monomer to control agent. Generally, the molar ratio of
monomer to control agent is in the range of from about 5 to about
5000, more preferably in the range of from about 10 to about 2000,
and most preferably from 10 to about 1500.
[0050] A free radical source is provided in the polymerization
mixture, which can stem from spontaneous free radical generation
upon heating or preferably from a free radical initiator. In the
latter case the initiator is added to the polymerization mixture at
a concentration high enough to for an acceptable polymerization
rate (e.g., commercially significant conversion in a certain period
of time, such as listed below). Conversely, a too high free radical
initiator to control agent ratio will favor unwanted dead polymer
formation through radical-radical coupling reaction leading to
polymer materials with uncontrolled characteristics. The molar
ratio of free radical initiator to control agent for polymerization
are typically in the range of from about 2:1 to about 0.005:1. The
ratios of control agent to initiator to monomer are used to target
a desired degree of polymerization, which is typically about 200 or
higher and more specifically about 500 or higher. Number average
molecular weights of the polymers are about 20,000 or higher, and
more specifically about 50,000 or higher.
[0051] Polymerization conditions also include the time for
reaction, which may be from about 0.5 hours to about 72 hours,
preferably in the range of from about 1 hour to about 24 hours,
more preferably in the range of from about 2 hours to about 12
hours. Conversion of monomer to polymer is at least about 70%, more
preferably at least about 75% and even more preferably at least
about 80%. The conversion measurement is done by gas chromatography
(GC) analysis based on the disappearance of monomer.
[0052] The polymerization process generally proceeds in a "living"
type manner. Thus, generally an approximately linear relationship
between conversion and number average molecular weight can be
observed, although this is not a pre-requisite. The living
character manifests itself by the ability to prepare block
copolymers: hence, a polymer chain is first grown with monomer A,
and then, when monomer A is depleted, monomer B is added to extend
the first block of polymer A with a second block of polymer B.
Block copolymer formation through a living process can be
demonstrated using analytical techniques such as polymer
fractionation with selective solvent (of polymer A, polymer B,
respectively), gradient elution chromatography and/or 2-dimensional
chromatography. Block copolymers tend to microphase-separate and
organize in a variety of morphologies that can be probed by
physical techniques such as X-ray diffraction, dynamic mechanical
testing, and the like.
[0053] Initiators, as discussed above, may be optional. When
present, initiators useful in the polymerization mixture and the
inventive process are known in the art, and may be selected from
the group consisting of alkyl peroxides, substituted alkyl
peroxides, aryl peroxides, substituted aryl peroxides, acyl
peroxides, alkyl hydroperoxides, substituted alkyl hydroperoxides,
aryl hydroperoxides, substituted aryl hydroperoxides, heteroalkyl
peroxides, substituted heteroalkyl peroxides, heteroalkyl
hydroperoxides, substituted heteroalkyl hydroperoxides, heteroaryl
peroxides, substituted heteroaryl peroxides, heteroaryl
hydroperoxides, substituted heteroaryl hydroperoxides, alkyl
peresters, substituted alkyl peresters, aryl peresters, substituted
aryl peresters, and azo compounds. Specific initiators include
benzoylperoxide (BPO) and AIBN. The polymerization mixture may use
a reaction media is typically either an organic solvent or bulk
monomer or neat. Optionally, after the polymerization is over
(e.g., completed or terminated) the thio-moiety (e.g., a
dithio-moiety) of the control agent can be cleaved by chemical or
thermal ways, if one wants to reduce the sulfur content of the
polymer and prevent any problems associated with presence of the
control agents chain ends, such as odor or discoloration. Typical
chemical treatment includes the catalytic or stoichiometric
addition of base such as a primary amine, acid or anhydride, or
oxidizing agents such as hypochlorite salts.
[0054] Generally, monomers that may be polymerized using the
methods of this invention (and from which M, below, may be derived)
include at least one monomer is selected from the group consisting
of styrene, substituted styrene, alkyl acrylate, substituted alkyl
acrylate, alkyl methacrylate, substituted alkyl methacrylate,
acrylonitrile, methacrylonitrile, acrylamide, methacrylamide,
N-alkylacrylamide, N-alkylmethacrylamide, N,N-dialkylacrylamide,
N,N-dialkylmethacrylamide, isoprene, butadiene, ethylene, vinyl
acetate and combinations thereof. Functionalized versions of these
monomers may also be used. Specific monomers or comonomers that may
be used in this invention include methyl methacrylate, ethyl
methacrylate, propyl methacrylate (all isomers), butyl methacrylate
(all isomers), 2-ethylhexyl methacrylate, isobornyl methacrylate,
methacrylic acid, benzyl methacrylate, phenyl methacrylate,
methacrylonitrile, .alpha.-methylstyrene, methyl acrylate, ethyl
acrylate, propyl acrylate (all isomers), butyl acrylate (all
isomers), 2-ethylhexyl acrylate, isobornyl acrylate, acrylic acid,
benzyl acrylate, phenyl acrylate, acrylonitrile, styrene, glycidyl
methacrylate, 2-hydroxyethyl methacrylate, hydroxypropyl
methacrylate (all isomers), hydroxybutyl methacrylate (all
isomers), N,N-dimethylaminoethyl methacrylate,
N,N-diethylaminoethyl methacrylate, triethyleneglycol methacrylate,
itaconic anhydride, itaconic acid, glycidyl acrylate,
2-hydroxyethyl acrylate, hydroxypropyl acrylate (all isomers),
hydroxybutyl acrylate (all isomers), N,N-dimethylaminoethyl
acrylate, N,N-diethylaminoethyl acrylate, triethyleneglycol
acrylate, methacrylamide, N-methylacrylamide,
N,N-dimethylacrylamide, N-tert-butylmethacrylamide,
N-n-butylmethacrylamide, N-methylolmethacrylamide,
N-ethylolmethacrylamide, N-tert-butylacrylamide,
N-n-butylacrylamide, N-methylolacrylamide, N-ethylolacrylamide,
4-acryloylmorpholine, vinyl benzoic acid (all isomers),
diethylaminostyrene (all isomers), .alpha.-methylvinyl benzoic acid
(all isomers), diethylamino .alpha.-methylstyrene (all isomers),
p-vinylbenzene sulfonic acid, p-vinylbenzene sulfonic sodium salt,
trimethoxysilylpropyl methacrylate, triethoxysilylpropyl
methacrylate, tributoxysilylpropyl methacrylate,
dimethoxymethylsilylpropyl methacrylate, diethoxymethylsilylpropyl
methacrylate, dibutoxymethylsilylpropyl methacrylate,
diisopropoxymethylsilylpropyl methacrylate, dimethoxysilylpropyl
methacrylate, diethoxysilylpropyl methacrylate, dibutoxysilylpropyl
methacrylate, diisopropoxysilylpropyl methacrylate,
trimethoxysilylpropyl acrylate, triethoxysilylpropyl acrylate,
tributoxysilylpropyl acrylate, dimethoxymethylsilylpropyl acrylate,
diethoxymethylsilylpropyl acrylate, dibutoxymethylsilylpropyl
acrylate, diisopropoxymethylsilylpropyl acrylate,
dimethoxysilylpropyl acrylate, diethoxysilylpropyl acrylate,
dibutoxysilylpropyl acrylate, diisopropoxysilylpropyl acrylate,
maleic anhydride, N-phenylmaleimide, N-butylmaleimide, butadiene,
isoprene, chloroprene, ethylene, vinyl acetate and combinations
thereof.
[0055] Polymers
[0056] The polymers formed with the chain transfer agents of this
invention are believed to be grown via a degenerative transfer
mechanism. Thus, upon analysis of the obtained polymers, monomers
might appear between the R.sup.1--S bond, and any of the above
formulas can be rewritten in a polymeric form. For example, the
polymers of this invention may be characterized by the general
formula: 7
[0057] wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 each have the
above definitions, M is a monomer or mixture of monomers or at
least 2 blocks of different monomer (any from the above lists) and
n is the degree of polymerization. For the multifunctional
embodiments of this invention, the (M).sub.n group appears in the
same place in formula II.
[0058] As discussed above, the polymers of this invention have a
narrow molecular weight distribution (or polydispersity index), as
measured by gel permeation chromatography against polystyrene
standards. The polydispersity index is less than 1.10 and more
specifically less than 1.07. Moreover, the molecular weight
distribution is generally mono-modal. In this context, mono-modal
distributions are shown in FIGS. 1 and 2, while non-mono-modal
distributions are shown in FIGS. 3, 4, 5 and 6. For purposes of
this invention, the slight shoulder in FIG. 2, for example, does
not remove the exemplified distribution from being considered
mono-modal, and in comparison, the much more pronounced
shoulder/peak in FIGS. 5 and 6 removes these exemplified
distributions from being considered mono-modal,
[0059] As used herein, "block copolymer" refers to a polymer
comprising at least two segments of differing composition; having
any one of a number of different architectures, where the monomers
are not incorporated into the polymer architecture in a solely
statistical or uncontrolled manner. Although there may be three,
four or more monomers in a single block-type polymer architecture,
it will still be referred to herein as a block copolymer. In some
embodiments, the block copolymer will have an A-B architecture
(with "A" and "B" representing the monomers). Other architectures
included within the definition of block copolymer include A-B-A,
A-B-A-B, A-B-C, A-B-C-A, A-B-C-A-B, A-B-C-B, A-B-A-C (with "C"
representing a third monomer), and other combinations that will be
obvious to those of skill in the art. Block copolymers can be
prepared a number of ways, especially including sequential addition
of monomers.
[0060] In another embodiment, the block copolymers of this
invention include one or more blocks of random copolymer together
with one or more blocks of single monomers. Thus, a polymer
architecture of A-R, A-R-B, A-B-R, A-R-B-R-C, etc. is included
herein, where R is a random block of monomers A and B or of
monomers B and C. Moreover, the random block can vary in
composition or size with respect to the overall block copolymer. In
some embodiments, for example, the random block R will account for
between 5 and 80% by weight of the mass of the block copolymer. In
other embodiments, the random block R will account for more or less
of the mass of the block copolymer, depending on the application.
Furthermore, the random block may have a compositional gradient of
one monomer to the other (e.g., A:B) that varies across the random
block in an algorithmic fashion, with such algorithm being either
linear having a desired slope, exponential having a desired
exponent (such as a number from 0.1-5) or logarithmic. The random
block may be subject to the same kinetic effects, such as
composition drift, that would be present in any other radical
copolymerization and its composition, and size may be affected by
such kinetics, such as Markov kinetics. Any of the monomers listed
elsewhere in this specification may be used in the block copolymers
of this invention.
[0061] A "block" within the scope of the block copolymers of this
invention typically comprises about 10 or more monomers of a single
type (with the random blocks being defined by composition and/or
weight percent, as described above). In preferred embodiments, the
number of monomers within a single block is about 15 or more, about
20 or more or about 50 or more. However, in an alternative
embodiment, the block copolymers of this invention include blocks
where a block is defined as two or more monomers that are not
represented elsewhere in the copolymer. This definition is intended
to encompass adding small amounts of a second monomer at one or
both ends of a substantially homopolymeric polymer. In this
alternative embodiment, the same copolymer architectures discussed
above apply. This definition is therefore intended to include
telechelic polymers, which include one or more functional end
groups capable of reacting with other molecules. Thus, generally, a
telechelic polymer is a block copolymer with in the definitions of
this invention. The functional groups present at one or both ends
of a telechelic polymer may be those known to those of skill in the
art, including, for example, hydroxide, aldehyde, carboxylic acid
or carboxylate, halogen, amine and the like, which have the ability
to associate or form bonds with another molecule. Likewise, the
block copolymers of the invention are intended to encompass
telechelic polymers containing bifunctional groups, such as
allyl-terminated or vinyl-terminated telechelics, sometimes
referred to as macromonomers or macromers because of their ability
to participate in polymerization reactions through the terminal
functional group.
[0062] Combining the above embodiments provides particularly
powerful method of designing block copolymers. For example, a block
copolymer may have the architecture F-A-B-F, where F represents
functional groups that may be the same or different within a single
F-A-B-F structure (which, therefore, may encompass F-A-B-F'). Other
block copolymer architectures within the scope of this invention
include A-R-B-F and F-A-R-B-F. Other architectures will be apparent
to those of skill in the art upon review of this specification.
[0063] In one embodiment, block copolymers are assembled by the
sequential addition of different monomers or monomer mixtures to
living polymerization reactions. In another embodiment, the
addition of a pre-assembled functionalized block (such as a
telechelic oligomer or polymer) to a living free radical
polymerization mixture yields a block copolymer. Ideally, the
growth of each block occurs to high conversion.
EXAMPLES
[0064] General: Syntheses of control agents were carried out under
a nitrogen or argon atmosphere. Other chemicals were purchased from
commercial sources and used as received, except for monomers, which
were filtered through a short column of basic aluminium oxide to
remove any inhibitor and degassed by applying vacuum. All
polymerization mixtures were prepared in a glove box under a
nitrogen or argon atmosphere and sealed, and polymerization was
conducted at 60.degree. C. or 70.degree. C. Size Exclusion
Chromatography was performed using automated conventional GPC
system where THF was used as the mobile phase with
polystyrene-based columns. All of the molecular weight results
obtained are relative to linear polystyrene standards. Gas
chromatography (GC) was carried out using a HP 8900 series GC.
Example 1
Control Agent Synthesis
[0065] 8
[0066] A 100 mL round-bottomed flask equipped with a magnetic stir
bar and maintained under a nitrogen atmosphere was charged with
pyrazole A'-1 (1.36 g, 20 mmol), sodium hydroxide (0.8 g, 20 mmol),
and DMSO (40 mL). The reaction mixture was kept in an ice/water
bath. To the resulting solution, carbon disulfide (1.2 mL, 20 mmol)
was added dropwise. The mixture was stirred for an additional one
hour after the addition was finished. Ethyl 2-bromopropionate (2.6
mL, 20 mmol) was then added to the reaction mixture dropwise. After
the reaction was completed, as monitored by TLC, the reaction
mixture was poured into 80 mL of water and followed by extraction
with ethyl acetate (2.times.80 mL). The organic layer was further
washed with water (2.times.80 mL) and dried over MgSO.sub.4. The
solvent was removed under reduced pressure and the product was
further purified by flash chromatograph. The desired control agent
A-1 was obtained in 85% yield (4.15 g).
Example 2
[0067] This example provides a comparison of the control agent of
example 1 in this invention and two similar control agents (shown
below) that were disclosed in WO 99/31144. Control agents B-1 and
B-2 were prepared in the same way as control agent A-1. 9
[0068] Each of the polymerizations was carried out in the same
general way. n-Butyl acrylate was used as the only monomer in the
amount of 3 mmol (430 uL) in all runs.
2,2'-Azobis(2-methylpropionitrile)(AIBN) was the initiator used in
each polymerization in a quantity of 5 mole % relative to the
control agent. Two control agent contents (0.015 mmol and 0.006
mmol) are employed to give a targeted degree of polymerization of
200 DP and 500 DP respectively. The polymerization mixture of each
reaction was created by automated dispensing of reaction components
at ambient temperature into a glass vial, which was then sealed.
Each polymerization was carried out at 60.degree. C. for the
desired time. The results of these polymerizations are reported in
Table 1. The GPC trace of each run is shown in FIGS. 1-6.
1 TABLE 1 Targeted Con- Control Degree of Reaction version Run
Agent Polmerization Time (h) (%) Mn Mw/Mn 1 A-1 200 12 77 22407
1.06 2 A-1 500 24 78 45022 1.08 3 B-1 200 12 81 29812 1.2 4 B-1 500
24 83 63385 1.26 5 B-2 200 12 80 26247 1.12 6 B-2 500 24 85 55312
1.19
[0069] It is to be understood that the above description is
intended to be illustrative and not restrictive. Many embodiments
will be apparent to those of skill in the art upon reading the
above description. The scope of the invention should, therefore, be
determined not with reference to the above description, but should
instead be determined with reference to the appended claims, along
with the full scope of equivalents to which such claims are
entitled. The disclosures of all articles and references, including
patent applications and publications, are incorporated herein by
reference for all purposes.
* * * * *