U.S. patent application number 08/924790 was filed with the patent office on 2001-08-02 for nanocomposites of dendritic polymers.
Invention is credited to BALOGH, LAJOS, TOMALIA, DONALD A..
Application Number | 20010011109 08/924790 |
Document ID | / |
Family ID | 25450733 |
Filed Date | 2001-08-02 |
United States Patent
Application |
20010011109 |
Kind Code |
A1 |
TOMALIA, DONALD A. ; et
al. |
August 2, 2001 |
NANOCOMPOSITES OF DENDRITIC POLYMERS
Abstract
In the present invention, an inorganic reactant is, or reactants
are, localized with respect to a dendritic polymer by physical
constraint within or by a non-covalent conjugation to the dendritic
polymer. The localized inorganic reactant or reactants is/are
subsequently transformed to form a reaction product which is
immobilized with respect to the dendritic polymer. This
immobilization occurs on a nanoscopic scale as a consequence of the
combined effects of structural, chemical and physical changes
without having covalent bonds between the product(s) and the
dendritic container and results in new compositions of matter
called dendritic nanocomposites. The resulting nanocomposite
material can be used to produce revolutionary products such as
water soluble elemental metals, with specific applications
including magnetic resonance imaging, catalytic, magnetic, optical,
photolytic and electroactive applications.
Inventors: |
TOMALIA, DONALD A.;
(MIDLAND, MI) ; BALOGH, LAJOS; (MIDLAND,
MI) |
Correspondence
Address: |
DONALD A TOMALLA & LAJOS BALOGH
695 KENMOOR SE
P O BOX 2567
GRAND RAPIDS
MI
49501
|
Family ID: |
25450733 |
Appl. No.: |
08/924790 |
Filed: |
September 5, 1997 |
Current U.S.
Class: |
523/105 ;
521/184 |
Current CPC
Class: |
Y10S 977/788 20130101;
B82Y 30/00 20130101; C08G 83/003 20130101; C08J 2300/00 20130101;
C08J 3/02 20130101; C08J 2300/202 20130101; Y10S 977/754 20130101;
Y10S 977/753 20130101; Y10S 977/835 20130101 |
Class at
Publication: |
523/105 ;
521/184 |
International
Class: |
C08J 003/00; C08G
063/44 |
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. A method of forming a composite composition comprising:
localizing at least one inorganic or organic reactant with respect
to a dendritic polymer by physical constraint, by non-covalent
interaction, or by both physical constraint and non-covalent
interaction; and transforming the reactant or reactants into a
reaction product which is dispersed at a nanoscale level in the
composite as a discrete entity having a size and size-distribution
which is determined and controlled by the dendritic polymer, and in
which the reaction product is constrained with respect to the
dendritic polymer, non-covalently conjugated to the dendritic
polymer or both.
2. The method of claim 1 further comprising the step of
distributing the composite composition into a polymeric matrix
material, after transforming the reactant or reactants.
3. The method of claim 1, in which the dendritic polymer is
distributed in a polymeric matrix before the inorganic reactant is
or reactants are, localized and transformed.
4. The method of claim 2, in which the dendritic polymer is
decomposed within the polymeric matrix after the reactant is, or
reactants are, localized and transformed.
5. The method of claim 3, in which the dendritic polymer is
decomposed within the polymeric matrix after the reactant is, or
reactants are, localized and transformed.
6. The method of claim 1, in which the dendritic polymer is a
dendrimer, a hyperbranched dendritic polymer, a dendrigraft, a
dendritic copolymer, a crosslinked dendrimer, a covalently linked
dendrimer cluster, or a combination thereof.
7. The method of claim 1, wherein the first reactant is localized
within the interior of the dendritic polymer molecule by
non-covalent bonding with the interior of the dendritic polymer
molecule.
8. The method of claim 7, wherein the non-covalent bonding of the
first reactant with the interior of the dendritic polymer molecule
comprises an ionic bond, a hydrogen bond, donor-acceptor bond, a
coordinative bond, Van der Waal interactions, or London dispersion
forces.
9. The method of claim 1, wherein the reaction product is
constrained within the dendritic polymer molecule by non-covalent
bonding with the interior of the dendritic polymer molecule.
10. The method of claim 9, wherein the non-covalent bonding of the
reaction product with the interior of the dendritic polymer
molecule comprises an ionic bond, a hydrogen bond, Van der Waal
interactions, or London dispersion forces.
11. The method of claim 1, wherein the reaction product is
physically constrained within the interior of the dendritic polymer
molecule.
12. The method of claim 1 in which the dendritic polymer has a
diameter of from about 10 to about 1,000 Angstroms.
13. The method of claim 1 in which the dendritic polymer has a
diameter of from about 10 to about 600 Angstroms.
14. The method of claim 1 in which the dendritic polymer is a dense
star polymer.
15. The method of claim 14 in which the dense star polymer has a
spheroid shape, an ellipsoid shape, or a rod shape.
16. The method of claim 14 in which the dense star polymer is a
poly(amidoamine) dendrimer.
17. The method of claim 16 in which the poly(amidoamine) dense star
polymer has a diameter of from about 40 to about 130 Angstroms.
18. The method of claim 1 in which the dendritic polymer molecule
includes at least two dense star polymer molecules ionically,
physically or covalently bonded to each other.
19. The method of claim 1 in which the dendritic polymer is a
poly(propylenamine) dendrimer.
20. The method of claim 1 in which the dendritic polymer includes
asymmetric branch cells.
21. The method of claim 1 in which the dendritic polymer is a
polyester dendrimer.
22. The method of claim 1 in which the product of the first and
second reactants is insoluble in a solvent in which the dendritic
polymer is soluble.
23. The method of claim 1 in which the dendritic polymer molecule
and the reactant or reactants are all soluble in a selected
solvent, the method including solubilizing the dendritic polymer
molecule and the first and second reactants in the selected solvent
and reacting the first and second reactants in solution phase.
24. The method of claim 1 in which reactant or reactants are
soluble in a selected solvent in which the dendritic polymer
molecule is insoluble, the method including solubilizing the
reactants in the selected solvent and reacting the first and second
reactants in a solution or gas phase.
25. The method of claim 1 in which the dendritic polymer molecule
is soluble in a first phase and insoluble in a second phase in
which the reactant or reactants are soluble, and wherein the
reactants pass through an interphase between the phases into the
interior of the dendritic polymer molecule.
26. A composite composition prepared by localizing at least one
organic or inorganic reactant with respect to a dendritic polymer
by physical constraint, by non-covalent interaction, or by both
physical constraint and non-covalent interaction; and transforming
the reactant or reactants into a reaction product which is
dispersed at a nanoscale level in the composite as a discrete
entity having a size and size-distribution which is determined and
controlled by the dendritic polymer, and in which the reaction
product is constrained with respect to the dendritic polymer,
non-covalently conjugated to the dendritic polymer or both.
27. The method of claim 26 further comprising the step of
distributing the composite composition into a polymeric matrix
material, after transforming the reactant or reactants.
28. The method of claim 26, in which the dendritic polymer is
distributed in a polymeric matrix before the inorganic reactant is,
or reactants are, localized and transformed.
29. The method of claim 27, in which the dendritic polymer is
decomposed within the polymeric matrix after the reactants is, or
reactants are, localized and transformed.
30. The method of claim 28, in which the dendritic polymer is
decomposed within the polymeric matrix after the reactant is, or
reactants are, localized and transformed.
31. The method of claim 26, in which the dendritic polymer is a
dendrimer, a hyperbranched dendritic polymer, a dendrigraft, a
dendritic copolymer, a crosslinked dendrimer, a covalently linked
dendrimer cluster, or a combination thereof.
32. The method of claim 26, wherein the first reactant is localized
within the interior of the dendritic polymer molecule by
non-covalent bonding with the interior of the dendritic polymer
molecule.
33. The method of claim 32, wherein the non-covalent bonding of the
first reactant with the interior of the dendritic polymer molecule
comprises an ionic bond, a hydrogen bond, donor-acceptor or
coordination bond, Van der Waal interactions, or London dispersion
forces.
34. The method of claim 26, wherein the reaction product is
constrained within the dendritic polymer molecule by non-covalent
bonding with the interior of the dendritic polymer molecule.
35. The method of claim 34, wherein the non-covalent bonding of the
reaction product with the interior of the dendritic polymer
molecule comprises an ionic bond, a hydrogen bond, a donor-acceptor
or coordination bond, Van der Waal interactions, or London
dispersion forces.
36. The method of claim 26, wherein the reaction product is
physically constrained within the interior of the dendritic polymer
molecule.
37. The method of claim 26, in which the dendritic polymer has a
diameter of from about 10 to about 1,000 Angstroms.
38. The method of claim 26, in which the dendritic polymer has a
diameter of from about 10 to about 600 Angstroms.
39. The method of claim 26, in which the dendritic polymer is a
dense star polymer.
40. The method of claim 39, in which the dense star polymer has a
spheroid shape, an ellipsoid shape, or a rod shape.
41. The method of claim 39, in which the dense star polymer is a
poly(amidoamine) dendrimer.
42. The method of claim 41, in which the poly(amidoamine) dense
star polymer has a diameter of from about 40 to about 130
Angstroms.
43. The method of claim 26, in which the dendritic polymer molecule
includes at least two dense star polymer molecules ionically,
physically or covalently bonded to each other.
44. The method of claim 26, in which the dendritic polymer is a
poly(polypropylenamine) dendrimer.
45. The method of claim 26, in which the dendritic polymer includes
asymmetric branch cells.
46. The method of claim 26, in which the dendritic polymer is a
polyester dendrimer.
47. The method of claim 26, in which the product of the first and
second reactants is insoluble in a solvent in which the dendritic
polymer is soluble.
48. The method of claim 26, in which the dendritic polymer
molecule,and the reactant or reactants are all soluble in a
selected solvent, the method including solubilizing the dendritic
polymer molecule and the first and second reactants in the selected
solvent and reacting the first and second reactants in solution
phase.
49. The method of claim 26, in which reactant or reactants are
soluble in a selected solvent in which the dendritic polymer
molecule is insoluble, the method including solubilizing the
reactants in the selected solvent and reacting the first and second
reactants in a solution or gas phase.
50. The method of claim 26, in which the dendritic polymer molecule
is soluble in a first phase and insoluble in a second phase in
which the reactant or reactants are soluble, and wherein the
reactants pass through an interphase between the phases into the
interior of the dendritic polymer molecule.
51. A method of forming a composite composition comprising:
providing a dendritic polymer having an interior and a surface
which is sufficiently permeable to allow at least one molecule of
at least one reactant to enter the interior; introducing the
reactant or reactants into the interior of the dendritic polymer;
and reacting the reactant or reactants to form a product which is
constrained within the interior of the dendritic polymer, without
forming a covalent bond between the dendritic polymer and the
reactant or reactants or their reaction product.
52. The method of claim 51, wherein the first reactant is localized
within the interior of the dendritic polymer molecule by
non-covalent bonding with the interior of the dendritic polymer
molecule.
53. The method of claim 52, wherein the non-covalent bonding of the
reactant or reactants with the interior of the dendritic polymer
molecule comprises an ionic bond, a hydrogen bond, a donor-acceptor
interaction, coordination bond, Van der Waal interactions, or
London dispersion forces.
54. The method of claim 51, wherein the reaction product is
constrained within the dendritic polymer molecule by non-covalent
bonding with the dendritic polymer molecule.
55. The method of claim 54, wherein the non-covalent bonding of the
reaction product with the interior of the dendritic polymer
molecule comprises an ionic bond, a hydrogen bond, a donor-acceptor
interaction, a coordinative bond, Van der Waal interactions, or
London dispersion forces.
56. The method of claim 51, wherein the reaction product is
physically constrained within the interior of the dendritic polymer
molecule.
57. The method of claim 51 in which the dendritic polymer has a
diameter of from about 10 to about 1,000 Angstroms.
58. The method of claim 51 in which the dendritic polymer has a
diameter of from about 10 to about 600 Angstroms.
59. The method of claim 51 in which the dendritic polymer is a
dense star polymer.
60. The method of claim 59 in which the dense star polymer has a
spheroid shape, an ellipsoid shape, or a rod shape.
61. The method of claim 59 in which the dense star polymer is a
poly(amidoamine) dendrimer.
62. The method of claim 61 in which the poly(amidoamine) dense star
polymer has a diameter of from about 40 to about 130 Angstroms.
63. The method of claim 51 in which the dendritic polymer molecule
includes at least two dense star polymer molecules ionically,
physically or covalently bonded to each other.
64. The method of claim 51 in which the dendritic polymer is a
poly(propylenamine) dendrimer.
65. The method of claim 51 in which the dendritic polymer includes
asymmetric branch cells.
66. The method of claim 51 in which the dendritic polymer is a
dendrigraft.
67. The method of claim 51 in which the dendritic polymer is a
hyperbranched polymer.
68. The method of claim 51 in which the dendritic polymer is a
polyester dendrimer.
69. The method of claim 51 in which the product of the first and
second reactants is insoluble in a solvent in which the dendritic
polymer is soluble.
70. The method of claim 51 in the dendritic polymer molecule, and
the reactant or reactants are all soluble in a selected solvent,
the method including solubilizing the dendritic polymer molecule
and the first and second reactants in the selected solvent and
reacting the first and second reactants in solution phase.
71. The method of claim 51 in which reactant or reactants are
soluble in a selected solvent in which the dendritic polymer
molecule is insoluble, the method including solubilizing the
reactants in the selected solvent and reacting the first and second
reactants in a solution or gas phase.
72. The method of claim 51 in which the dendritic polymer molecule
is soluble in a first phase and insoluble in a second phase in
which the reactant or reactants are soluble, and wherein the
reactants pass through an interphase between the phases into the
interior of the dendritic polymer molecule.
73. A composite composition comprising: a dendritic polymer
molecule having an interior, and a reaction product constrained
within the interior of the dendritic polymer molecule, the reaction
product being formed by reaction between first and second reactants
which are capable of entering the interior of the dendritic polymer
molecule, without forming a covalent bond between the dendritic
polymer and either the first or second reactants or their reaction
product.
74. The composite composition of claim 73, wherein the first
reactant is localized within the interior of the dendritic polymer
molecule by non-covalent bonding with the interior of the dendritic
polymer molecule.
75. The composite composition of claim 74, wherein the non-covalent
bonding of the first reactant with the interior of the dendritic
polymer molecule comprises an ionic bond, a hydrogen bond, a
donor-acceptor bond, a coordination bond, Van der Waal
interactions, or London dispersion forces.
76. The composite composition of claim 73, wherein the reaction
product is constrained within the dendritic polymer molecule by
non-covalent bonding with the interior of the dendritic polymer
molecule.
77. The composite composition of claim 76, wherein the non-covalent
bonding of the reaction product with the dendritic polymer molecule
comprises an ionic bonding, a hydrogen bond, a donor-acceptor bond,
a coordination bond, Van der Waal interactions, or London
dispersion forces.
78. The composite composition of claim 73, wherein the reaction
product is physically constrained within the interior of the
dendritic polymer molecule.
79. The composite composition of claim 73 in which the dendritic
polymer has a diameter of from about 10 to about 1,000
Angstroms.
80. The composite composition of claim 73 in which the dendritic
polymer has a diameter of from about 10 to about 600 Angstroms.
81. The composite composition of claim 73 in which the dendritic
polymer is a dense star polymer.
82. The composite composition of claim 81 in which the dense star
polymer is a poly(amidoamine) dendrimer.
83. The composite composition of claim 82 in which the dense star
poly(amidoamine) dendrimer has a diameter of from about 40 to about
130 Angstroms.
84. The composite composition of claim 83 in which the dendritic
polymer molecule includes at least two dense star polymer molecules
which have been ionically, physically or covalently bonded to each
other.
85. A composite composition of claim 83 in which the dendritic
polymer is a poly(propylenamine) dendrimer.
86. A composite composition of claim 83 in which the dendritic
polymer includes asymmetric branch cells.
87. A composite composition of claim 83 in which the dendritic
polymer is a dendrigraft.
88. A composite composition of claim 83 in which the dendritic
polymer is a hyperbranched polymer.
89. A composite composition of claim 83 in which the dendritic
polymer is a poly(ester) dendrimer.
90. A composite composition of claim 83 in which the product of the
first and second reactants is insoluble in a solvent in which the
dendritic polymer is soluble.
91. The composite composition of claim 73 in which at least one of
the reactants contains at least one metal atom which is responsive
to a magnetic field.
92. The method of claim 91, wherein the reagent which reacts with
the metal-dendritic polymer complex is an oxalate, and the solvent
dispersible complex is a metal oxalate/dendritic polymer
complex.
93. The method of claim 92, wherein the reagent which reacts with
the metal-dendritic polymer complex is a phosphate, and the solvent
dispersible complex is a metal phosphate/dendritic polymer
complex.
94. The method of claim 91, wherein the reagent which reacts with
the metal-dendritic polymer complex is a reducing agent, and the
solvent dispersible complex is a metal/dendritic polymer
complex.
95. A method of immobilizing a compound which is substantially
insoluble in a solvent in a soluble molecular scaffold, comprising
contacting a solution of reactants with a dendritic polymer to form
a dendritic polymer complex, and subsequently contacting the
dendritic polymer complex with a reagent which reacts with the
complex compound to form a solvent dispersible complex.
96. The method of claim 95, wherein the reactant solution is a
solution metal containing an acetate.
97. The method of claim 96, wherein the metal of the metal acetate
is cadmium, copper, zinc, lead, bismuth or manganese.
98. The method of claim 95, wherein the reactant solution is a
solution containing a metal sulfate.
99. The method of claim 98, wherein the metal ion of the metal
sulfate solution is iron.
100. The method of claim 95, wherein the reactant solution is a
solution containing a metal trifluorosulfonate solution.
101. The method of claim 90, wherein the metal ion of the metal
trifluorosulfonate solution is silver.
102. The method of claim 95, wherein the reagent which is reacted
with the metal-dendritic polymer complex is hydrogen sulfide gas,
and the solvent dispersible complex is a metal sulfide-dendritic
polymer complex.
103. The method of claim 95, wherein the reagent which reacts with
the metal-dendritic polymer complex is a halide ion, and the
solvent dispersible complex is a metal halide/dendritic polymer
complex.
104. The method of claim 95, wherein the reagent which reacts with
the metal-dendritic polymer complex is a hydroxyl ion, and the
solvent dispersible complex is a metal hydroxide/dendritic polymer
complex.
105. The method of claim 95, wherein the dendritic polymer is a
dendrimer.
106. The method of claim 95, wherein the dendritic polymer is a
dense star poly(amidoamine) dendrimer.
107. The method of claim 95, wherein the dendritic polymer is at
least a fourth generation polyamidoamine dendrimer.
108. The method of claim 96, wherein the polyamidoamine dendrimer
is modified to provide a hydrophobic surface which facilitates
solubility of the solvent-dispersible complex in a non-polar
solvent.
109. The method of claim 97, wherein the dendrimer is surface
modified by reaction with 1,2-epoxyalkane to provide a hydrophobic
surface which facilitates solubility of the solvent dispersible
complex in a non-polar solvent.
110. A metal-containing complex exhibiting improved solvent
dispersibility, comprising a metal compound, which is substantially
insoluble in a solvent, complexed with a dendritic polymer which is
soluble in the solvent.
111. The complex of claim 110, wherein the metal compound is a
metal sulfide.
112. The complex of claim 111, wherein the metal of the metal
sulfide is cadmium, copper, zinc, lead, iron, silver, cobalt,
mercury, bismouth or nickel.
113. The complex of claim 110, wherein the metal compound is a
metal halogenide.
114. The complex of claim 113, wherein the metal of the metal
halogenide is silver.
115. The complex of claim 110, wherein the metal compound is a
metal hydroxide.
116. The complex of claim 115, wherein the metal of the metal
hydroxide is silver, aluminum, copper or cobalt.
117. The complex of claim 110, wherein the metal compound is
elemental metal.
118. The complex of claim 117, wherein the elemental metal is
silver, copper, gold, iron, cobalt or nickel.
119. The complex of claim 110, wherein the dendritic polymer is a
dendrimer.
120. The complex of claim 110, wherein the dendritic polymer is a
polyamidoamine dendrimer.
121. The complex of claim 110, wherein the dendritic polymer is at
least a fourth generation polyamidoamine dendrimer.
122. The complex of claim 110, wherein the metal is a copper
oxide.
123. The complex of claim 110, wherein the metal compound is uranyl
phosphate.
124. The complex of claim 110, wherein the dendritic polymer is
hydrophobically modified.
125. The complex of claim 124, wherein the dendritic polymer is
hydrophobically modified by reaction with an epoxy alkane.
126. The complex of claim 125, wherein the metal compound is a
metal sulfide, and wherein the metal is copper, silver, cadmium,
iron, nickel, manganese, calcium, gadolinium, or aluminum.
127. A method of forming a composite composition comprising:
contacting a first reactant with a dendritic polymer molecule
having an interior which is accessible to the first reactant, the
first reactant being capable of entering the interior of the
dendritic polymer molecule and being localized within the interior
of the dendritic polymer molecule; and contacting the dendritic
polymer and the first reactant localized within the interior of the
dendritic polymer with a second reactant which is capable of
entering the interior of the dendritic polymer molecule and
reacting with the first reactant localized within the interior of
the dendritic polymer molecule to form a composite material
comprising the dendritic polymer molecule and a reaction product
constrained within the interior of the dendritic polymer molecule,
without forming a covalent bond between the dendritic polymer and
either the first or second reactants or their reaction product.
Description
FIELD OF THE INVENTION
[0001] This invention relates to the formation of novel
nanocomposites between dendritic polymers and a variety of
materials.
BACKGROUND OF THE INVENTION
[0002] The literature describes the formation of nanoparticles in
various classical polymers, such as organization and immobilization
of metal compounds in linear, branched and crosslinked polymers. In
particular, the literature describes immobilization of metals,
metal ions, and metal sulfides using ionomers, and block
copolymers.
[0003] Rules of complex formation are well known in physical
chemistry as a consequence of more than fifty years of extensive
research. Formation of such complexes may occur on the surface of
dendritic polymers or in their interior. These phenomena have been
described in many publications.
[0004] Preparation and analysis, physics and chemistry of nanosized
materials is described for instance in the series of books of
Kluver Academics On The Physics and Chemistry Of Materials With
Low-Dimension Structures, such as "Physics and Chemistry Of Metal
Cluster Compounds" edited by L. J. De Jongh, Kluver Academic,
Dordrecht/Boston/London, 1994, and references thereof. A general
drawback of the presently used methods of preparing nanosized
materials is that they either require sophisticated and expensive
instrumentation or tedious and extensive preparation and
purification processes. Simple preparation of transiently
stabilized nanosized materials in solution is possible by employing
a combination of small organic ligands and amphophilic molecules.
However, these clusters lack long-term stability. Also, a general
disadvantage with known methods of preparing nanosized materials is
that the size and size distribution of the resulting nanoparticles
obey statistical rules. As a result, preparation of nanoparticles
with a narrow size distribution requires tedious purification
procedures.
[0005] J U. Yue et al. have reported, in J Am. Chem. Soc. 1993,
115, 4409-4410, a technique for preparing nanosized materials
involving synthesis of zinc fluoride in
poly(2,3-trans-bis-tert-butylanildimethyl-n- orborn-5-ene) domains
within polymethyltetracyclododecene matrices, and interconversion
of the zinc fluoride clusters to zinc sulfide. Yue et al. concluded
that the disclosed method demonstrated a general approach for
carrying out a chemical reaction within a nanoscale region of a
block copolymer, and speculated that different kinds of clusters
can be synthesized from a given starting material. Yue et al.
hypothesized that lead sulfide and cadmium sulfide clusters can be
prepared using the general approach disclosed, and reported that
this same approach has been used to generate zinc sulfide quantum
clusters which are superior in quality to zinc sulfide clusters
generated using other techniques.
[0006] Martin Moller reported in Synthetic Metals, 1991, 41-43,
1159-1162, the synthesis of nanosized inorganic crystallites or
clusters of cadmium sulfide, cobalt sulfide, nickel sulfide and
zinc sulfide prepared from functionalized diblock copolymers of
polystyrene and poly-2-vinylpyridine. The diblock copolymers were
prepared with narrow molecular weight distributions by sequential
anionic polymerization. Films were prepared by solvent evaporation
with metal salts of copper, cadmium, cobalt, nickel, zinc and
silver. The films were subsequently treated with gaseous hydrogen
sulfide to form the corresponding metal sulfides.
[0007] W. Mahler, in Inorganic Chemistry, 1988, 27(3), 435-436,
reported the preparation of polymer-trapped semiconductor particles
by milling an ethylene-methacrylic acid copolymer with a metal
acetate or acetylacetonate at an elevated temperature (160.degree.
C.) to form a neutralized ionomer.
[0008] T Douglas et al. have reported in Science, Jul. 7, 1995 Vol.
269, 54-57, the synthesis of amorphous iron sulfide minerals
containing either 500 or 3000 iron atoms in each cluster. The
synthesis was achieved within the nanodimensional cavity of horse
spleen ferritin. The report indicates that the reaction of acidic
(pH 5.4) sulfide solutions within ferritin results in the in situ
nanoscale synthesis of protein encapsulated iron sulfides. Douglas
et al speculated that such bioinorganic nanoparticles might be
useful as biological sensors and markers, drug carriers, and
diagnostic and radioactive agents. More specifically,
magnetoferritin has shown potential as a contrast agent for
magnetic resonance imaging of tissue and uranium oxide-loaded
ferritin could have use in neutron-capture therapy. Douglas et al.
have also suggested that nanodimensional metal sulfides could be
useful in the preparation of semiconductors which could be of
technological, and perhaps biological importance.
[0009] Y Wang et al. have reported in J. Chem. Phys., 1987 87(12),
7315-7322, December 15, the preparation of nanodimensional lead
sulfide clusters in ethylene-methacrylic acid copolymers by
exchanging Pb.sup.2+ into the polymer film and then reacting the
resulting lead- resin complex with hydrogen sulfide.
[0010] J. P. Kuczynski et al. have reported in J. Phys. Chem.,
1984, 88, 980-984, the synthesis of cadmium sulfide in a Nafion
polymer film. Small cadmium sulfide crystalline particles were
reported to exhibit properties similar to those of cadmium sulfide
single crystals.
[0011] M. Krishnan et al. have reported in J Am. Chem. Soc., 1983,
105, No. 23, 7002-7003, a method of incorporating a dispersed
semiconductor (CdS) throughout an ionically conductive polymer
membrane (Nafion), in which a suitable redox couple and catalyst
can be added to promote photocatalytic reactions on the membranes.
The pre-treated membrane was immersed in a solution of Cd.sup.2+
(pH=1) to incorporate Cd.sup.2+30 in the membrane by ion exchange.
Subsequent exposure of the membrane to hydrogen sulfide produced
spherical cadmium sulfide particles of a diameter of one micrometer
or smaller. A cationic redox agent, such as methylviologen
(MV.sup.2+), can be incorporated into the membrane. Kishnan et al.
also reported that platinum can be incorporated into the
CdS/MV.sup.2+ membrane system, and have speculated that by
employing an analogous technique, incorporation of other
semiconductors, such as titanium oxide and zinc sulfide, should be
possible.
[0012] Albert W-H Mau et al. have reported in J Am. Chem. Soc.,
1984, 106, No. 22, 6335-6542, that hydrogen-production efficiencies
from water in photocatalytic reactions at cadmium sulfide
crystallites embedded in a polymer (Nafion) matrix containing a
hydrogen evolution catalyst (Pt) were greater than those observed
with unsupported colloidal or powdered semiconductors under similar
conditions.
[0013] Y Ng Cheong Chan et al. have reported, in Chem. Mater. 1992,
4, 885-894, methods for forming metal clusters that are less than
100 Angstroms in diameter, that have a narrow size distribution,
and that are dispersed evenly throughout a nonconductive polymer
matrix. These methods involve reduction of metal complexes and
aggregation of metal atoms in the solid state, either in an
organometallic homopolymer or in an organometallic block of a
microphase-separated diblock copolymer. Chan et al. suggest that
such compositions might exhibit discemable catalytic
properties.
[0014] In J Am. Chem Soc. 1992, 114, 7295-7296, Chan et al.
reported the synthesis of single silver nanoclusters evenly
dispersed within spherical microdomains of block copolymer
films.
[0015] Sung Soon Im et al. reported, in J Appl. Polym. Sci., 1992,
45, 827-836, the preparation of metallic sulfide and
polyacrylonitril (PAN) film composites which exhibit improved
electrical conductivity. The composites were prepared by a
chelating method in which PAN films were treated with ammonium
hydroxide solution to induce amidoxime groups which were
coordinated with Cu.sup.2+ and Cd.sup.2+ absorbed to the
amidoximated PAN films and subsequently treated with hydrogen
sulfide gas to form CuS-PAN and CdS-PAN composite films.
[0016] M. Francesca Ottaviani et al. reported in J Am. Chem. Soc.
1994, 116, 661-671, the preparation and characterization of
Cu.sup.2+ complexes formed with anionic polyamidoamine (PAMAM)
Starburst.RTM. dendrimers (SBDs). The PAMAM SBDs (generations
0.5-7.5) were subjected to hydrolysis of methyl ester-terminated
generations with stoichiometric amounts of sodium hydroxide in
methanol to form sodium carboxylate terminated PAMAM SBDs. The
carboxylated PAMAM SBDs were treated with aqueous
Cu(NO.sub.3).sub.2 solutions to obtain SBD/Cu(II) complexes.
Ottaviani et al. identified three different complexes of copper
using electron paramagnetic resonance technique, including
carboxylate complexes at low pH, Cu(II)-N.sub.2O.sub.2 complexes
involving interactions with nitrogen centers in the internal
permeable structure of the dendrimers at intermediate pH, and
Cu(II)-N.sup.3O or Cu(II)-N.sup.4 complexes involving a wide number
of internal sites at both higher pH and higher generation.
[0017] In J. Phys. Chem. 1996, 100, 11033-11042, Ottaviani et al.
disclosed the preparation and characterization of PAMAM-SBDs/Mn(II)
complexes. Ottaviani et al. concluded that Mn(II) does not interact
with amino-terminated full generation PAMAM-SBDs, and only
interacts probably at the second solvation shell, with surface
carboxylate groups of carboxylated half generation PAMAM-SBDs.
[0018] In J Phys. Chem. B., 1997, 101, 158-166, Ottaviani et al.
disclosed the preparation and characterization of PAMAM-SBDs/Cu(II)
complexes. Ottaviani et al. concluded that Cu(II) does interact
with amino-terminated full generation PAMAN-SBDs as a function of
pH. Three different complexes were found in the amino-terminated
PAMAM-SBDs, including Cu(II)-N.sub.2O.sub.2 complexes involving
interactions with nitrogen centers in the internal permeable
structure of the dendrimers at intermediate pH, Cu(II)-N.sub.3O
complexes and Cu(II)-N.sub.4 complexes.
[0019] In Polym. Prepr., ACS Div. Polym. Chem. 1995, 36, 239-240
Wege et al. reported the formation of polymer hybrids when methyl
acrylate and vinyl acetate polymerization was initiated by radical
initiators in the presence of PAMAM dendrimers. Depending on
reaction conditions, both water soluble and insoluble hybrids
formed. The drawback of such a process is, that the method is
limited to radically polymerizable organic monomers, and, the
reaction results in inseparable polymeric hybrid networks because
of the chain-transfer to dendrimer that results in covalent bonds
between the growing polymeric chain and the functional groups of
the host, thereby irreversibly eliminating the container-properties
of the dendrimers used.
[0020] In Eur. Pat. Appl. 95201373.8 (Publ. 0,684,044 A2), Meijer
et al. disclosed a composition consisting of a dendrimer and an
active substance. This composition is formed by mixing a dendrimer
with a previously synthesized compound and treating the surface of
the dendrimer with a blocking agent which is sterically of
sufficient size, which readily enters into a chemical bond with the
terminal groups of a dendrimer, and which can also be split off
from the dendrimer thereby controlling the release of partly or
fully occluded compounds. The drawback of such a process is that it
is limited to the inclusion of pre-existing compounds. Another
drawback is, that the method is limited to dendrimers having
identical and modifiable surface groups.
[0021] In U.S. Pat. No. 5,422,379, Newkome et al. disclose the
construction of unimolecular micelles that are able to reversibly
expand and contract as a response to a change in the environment.
These unimolecular micelles may have different structures and
active reaction sites which may complex metals.
SUMMARY OF THE INVENTION
[0022] The invention includes a variety of composite compositions
of matter in which discrete nanosized inorganic materials are
distributed on or in a polymeric material, and in which the size
and size-distribution of the distributed nanosized inorganic
materials are determined and controlled by a dendritic polymer. The
invention also contemplates various methods of forming composite
compositions of matter in which discrete nanosized inorganic
materials are distributed on or are in a polymeric material, and in
which the size and size-distribution of the distributed nanosized
inorganic materials are determined and controlled by a dendritic
polymer.
[0023] The methods generally include a first step involving a
non-covalent conjugation interaction between a dendritic polymer
and at least one inorganic material creating a conjugate, in which
the distribution of said inorganic material follows the motif of
size and size-distribution of the dendritic polymer, and, in which
both the dendritic polymer and the nanosized inorganic materials
conjugated to the dendritic polymer each retain their respective
identities as well as their respective physical and chemical
properties on account of the absence of covalent interaction
between these separate entities. In a second step, the nanosized
inorganic material or materials are reacted to form a
nanostructural composite material in which the reaction product is
constrained with respect to the dendritic polymer, without being
covalently bonded to the dendritic polymer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 shows interior scaffolding, container and surface
scaffolding properties in polyamidoamine dendrimers as a function
of generation, surface-group distances and probe-size.
[0025] FIG. 2 shows a simplified scheme of transforming dendritic
polymer molecules and a multiplicity of dendritic molecules into
intermediates and nanocomposites.
[0026] FIG. 3 is a unstained TEM micrograph of the {Cu.sup.2S-G4.T}
nanocomposite at a magnification of 200,000;
[0027] FIG. 3A is a comparison of SEC-chromatograms of PAMAM G4.T
dendrimer, and of five different nanocomposites (with Ag.sub.2S,
ZnS, CuS, Cu.sub.2S and CdS);
[0028] FIG. 3B is a comparison of the RP-IP-HPLC chromatogram of
PAMAM G4.T and the {Ag.sub.2S-G4T} nanocomposite wherein the
continuous line represents pure dendrimer and the dotted line
represents the nanocomposite;
[0029] FIG. 3C is a comparison of capillary electropherograms of
the host and two nanocomposites;
[0030] FIG. 4A is .sup.13C NMR spectrum of G4.T;
[0031] FIG. 4B is .sup.3C NMR spectrum of {ZnS-G4.T} (CH.sub.3COOH
signals are due to the starting material, the Zn(II)-acetate);
[0032] FIG. 5 is .sup.1H NMR spectrum of the {Cu.sub.2S-G4.T}
(CH.sub.3COOH signals originate from the Cu(II)-acetate starting
material);
[0033] FIG. 6 is a comparison of UV-visible spectra of PAMAM G4.T
and {Ag.sub.2S-G4.T}. [Ag.sub.2S]=7.78 mM, [G4.T]=0.25 mM, 2 mg/ml
solution, L=0.1 cm;
[0034] FIG. 7 is a comparison of the RP-IP-HPLC chromatogram of
G4.T and its complex with Cu-acetate wherein the continuous line
represents dendrimer and the dotted line represents the internal
Cu-complex;
[0035] FIG. 8 is a UV-visible spectrum of dendrated CdS in a
polypropylene cuvette;
[0036] FIG. 9 is a UV-visible spectrum of CoS in water in a
polypropylene cuvette;
[0037] FIG. 10 is a UV-vis spectrum of {AgOH-G4.T} i.e., a
dendrimer encapsulated AgOH;
[0038] FIG. 11 is a UV-vis spectrum of the dendrimer encapsulated
AgBr solution in MeOH stored in dark for 1 day, polypropylene
cuvette;
[0039] FIG. 12 is a UV-vis spectrum of AgBr solution in MeOH
photolysed for 1 hr. in a polypropylene cuvette; and
[0040] FIG. 13 is a comparison of UV-visible spectra of Cu.sup.2+
in water (Cu.sup.2,/W), the [Cu.sup.2+-G4.T] in toluene
(Cu.sup.2+/T) and CuS in toluene (CuS/T).
[0041] FIG. 14 is a graph of the absorbance of gold nanocolloides
formed in the presence of a G4.T PAMAM dendrimer in water.
[Au(0)]=33 mg/L.
[0042] FIG. 15 is a graphical comparison of the UV-visible spectrum
of the [CuAc.sub.2).sub.31-G4.(NHCHCH(OH)C.sub.4H.sub.10).sub.64]
molecular complex and the corresponding nanocomposite solution,
that contains elemental copper domains in the inverted dendritic
micelle.
[0043] FIG. 16 is an electron micrograph of colloidal gold.
[0044] FIG. 17 is an electron micrograph of colloidal gold.
[0045] FIG. 18 is an electron micrograph of colloidal gold,
brominated.
[0046] FIG. 19 is an electron micrograph of colloidal copper.
[0047] FIG. 20 is an electron micrograph of {CuS - G7.0} dendritic
nanocomposite.
[0048] FIG. 21 is an electron micrograph of {CuS - G9.0} dendritic
nanocomposite.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0049] The ability to fabricate nanometer-scale objects identically
replicated in unlimited quantities is an ultimate challenge in
modern materials research. Success in this area offers outstanding
fundamental and potential technological consequences.
[0050] This invention makes possible the definition of shape and
size of materials at a nanoscopic scale. This scale represents a
transition of physical and chemical properties between atomic and
bulk material. Successful, simple and economic preparation of
uniform nanomaterials is highly desirable. These novel
nanocomposites display new, surprising and an important physical
(such as solubility, optical, electronic, magnetic, etc.,) and
chemical properties (reactivity, selectivity, etc.).
[0051] The methods of this invention provide simple and economic
means for fabricating assemblies of nanometer-scale materials
identically replicated in unlimited quantities with a predetermined
composition, size, and size-distribution.
[0052] Combinations of "zero dimensional" dendritic building
blocks, i.e., dendrimers, dendrons, dendrigrafts and hyperbranched
polymers into multiple structures with 1-D, 2-D and 3-D
(dimensional) features such as chains, films, covalent and
non-covalent clusters, crosslinked dendritic polymers and dendritic
polymers afford a great structural and architectural variety for
nanocomposite preparation. Utilizing the periodic properties
(illustrated in FIG. 1) of these well-defined compounds, such as
interior scaffolding, container and surface scaffolding properties,
it is possible to define and control the size and size-distribution
of the dispersed phase(s) in composite materials or conventional
organic or inorganic polymers. Although FIG. 1 illustrates only the
periodic properties of PAMAM dendrimers with respect to one
particular metal ion, the periodicity of these three properties
will be similar for any dendritic polymer and any interacting
reactant. These periodic properties are the function size and
properties of the probe compared to the nature and distance of the
surface groups and the general structure of the dendritic polymer.
Only the borders between interior scaffolding, container and
surface scaffolding will be shifted.
[0053] The fundamental advantages of using dendritic polymers in
this procedure are their well defined structure, size and
size-distribution, and the fact, that they can contain guests or
carry them on their surface due to their interior ligand-structure
and variable surface structure.
[0054] It is also an advantage, that a molecular/atomic level of
mixing can be achieved in these nanocomposites due to the
nonspecific nature of diffusion in the first step. As a
consequence, a macro-homogenous material with extremely narrow
distributions in the dispersed phase can be obtained. A further
advantage is that the dendritic intermediates (conjugates,
precomposite materials) may be mixed, or they may be combined
according to the state-of-the-art methods of dendrimer chemistry.
Dendritic precomposites or composites may be further reacted with
bi- or multifunctional monomers, oligomers or polymers, as well as
dissolved or dispersed in a nonreactive matrix required by specific
applications. Mixtures of dendritic nanocomposites can provide
microheterogeneity at a nanoscopic level, expanding the methods of
nano-engineering.
[0055] The most characteristic property of these new composites is
that the pre-defined density-fluctuation of at least one component
is determined at a nanoscopic level fundamentally by the dendritic
polymer(s) used. This basic structure may also be influenced by the
chemistry of other components.
[0056] Thus, appropriately synthesized and selected 0-D, 1-D, 2-D
and 3-D dendritic polymer structures can be used as permanent or
temporary templates.
[0057] Individual ("zero dimensional") dendritic polymers, as well
as complexes of dendritic polymers, can be transformed into 1-D,
2-D and 3-D networks using their surface-functionalities. (In our
nomenclature, a "zero-dimensional" (0-D) unit is an individual
dendrimer, dendritic polymer or a dendritic cluster, a l-D notation
refers to chains, 2-D organizations refers to layers of
nanocomposites, while 3-D networks are crosslinked dendritic
polymers.) Similarly, 1-D, 2-D and 3-D dendritic networks may form
a complex with metals and metalloids. Such a conjugate may also
serve as a precursor to dendritic polymers with a higher
dimensionality or to a dendritic nanocomposite (FIG. 2). Any of the
0-D, 1-D, 2-D and 3-D formations may be dispersed in a
non-dendritic media (in either their physically or chemically
bonded forms) before or after the chemical transformation. When
this non-dendritic media is a gas, the product is a bulk of
dendritic polymers containing non-covalently bound and
nano-dispersed guest molecules (dendritic nanocomposites). When the
non-dendritic medis is a solvent, the product is the solution of
said nanocomposites. It may also be a suspension or emulsion. When
the non-dendritic media is a solid containing dispersed dendritic
nanocomposites, the product is a nanocomposite, in which the size
and distribution of dispersed phase is determined by the dendritic
nanocomposites. Dendritic polymers of any dimensional structure can
be used as permanent or temporary templates for fabricating
nanocomposites of metal and metalloid compounds. In these
nanocomposites metal and metalloid compounds are dispersed in
organic or inorganic matrices with a predetermined size and
size-distribution.
[0058] Starting from any dimensional stage (left column), first, a
temporary interaction (involving a non-covalent conjugation such as
complexation, H-bonding, dipole-dipole interactions, London
dispersion forces, Van der Waals interactions, etc.) is brought
about between appropriately selected dendritic polymers and the
first group of reactants (middle column). These intermediates then
are chemically transformed in one or more steps into novel
nanostructures (see FIG. 2) by either physical or chemical methods,
such as reaction, heat, illumination, etc.
[0059] In these composites the size and size-distribution of the
dispersed material(s) is determined and controlled by a dendritic
polymer. This dendritic polymer may be one of the components, but
also might be removed from the final product and its role is to
provide a template for the material to be dispersed. The continuous
phase of this final composite is not necessarily a dendritic
polymer.
[0060] The method for the preparation of dendritic nanocomposites
is carried out in two or more steps. The first step involves
localization of reactants (atoms, ions or molecules) within a
dendritic polymer.
[0061] Localization of a reactant refers to the reactant being
located proximate or within the interior of an intermediate
generation dendritic polymer for a period sufficient to enable
reaction with the second reactant to form a product which is
physically or chemically trapped within the interior of the
dendritic polymer; non-covalent conjugation with the interior
scaffolding of a lower generation dendritic polymer having a
structure which is relatively open and therefore does not have a
well defined surface which is capable of restricting access to the
interior scaffolding; and non-covalent conjugation with surface
groups on generally any generation of dendritic polymer.
Localization includes physical restraint of the reactant or
reactants in the interior of the dendritic polymer and non-covalent
bonding of the reactant or reactants with the interior or exterior
of the dendritic polymer. Physical restraint may range from
relatively transient containment of the reactant or reactants
within the interior of the dendritic polymer to relatively
permanent entrapment of the reactant or reactants in the interior
or exterior of the dendritic polymer. Non-covalent bonding of the
reactant or reactants with the interior or exterior of the
dendritic polymer includes ionic bonding, donor acceptor
interactions (coordination bonding), hydrogen bonding, Van der Waal
interactions, and London dispersion interactions. The invention
does not contemplate nanocomposites in which the dispersed phase is
covalently bonded to the dendritic polymer. Covalent bonding would
change the characteristics of the dendritic polymer and make it one
of the reactants and a part of the final reaction product, due to
the relatively irreversibility of covalent bonding. All of the
other attractive forces (e.g., physical restraint, ionic bonding,
coordination bonding, and hydrogen bonding) are, to a degree,
significantly more reversible than covalent bonding.
[0062] During the first step of the process, guest atoms, ions
and/or molecules diffuse to a dendritic macromolecule of
intermediate generation and these guest atoms, ions or molecules
become localized such as by physical restraint or non-covalent
interactions with the surface or interior of the intermediate
generation dendritic polymer; and/or guest atoms, ions and/or
molecules become non-covalently conjugated to the surface groups of
generally any generation of dendritic polymer; or guest atoms, ions
and/or molecules become non-covalently conjugated to interior
scaffolding or surface groups of a lower generation dendrimer.
Examples of non-covalent bonding between the guest atoms, ions
and/or molecules and the interior of the dendritic polymer molecule
include ionic bonding, hydrogen bonding, donor- acceptor,
coordination bonding, Van der Waals interactions, and London
dispersion forces. The driving force of the diffusion into the
interior or an intermediate generation dendrimer is the extremely
high local concentration of coordination moieties or active binding
sites (such as N, NH, O, P, etc. atoms) in the interior.
[0063] As opposed to small molecular complexing agents, dendritic
polymers do not hinder the formation of new chemical compounds, but
retain the new compound(s) in their interior or on their exterior
giving rise to revolutionary nanocomposites. Thus, chemical
transformation of the reactant(s) into a new chemical entity
results in organic-inorganic composites in which nanoscopic guest
molecules, clusters and nanoparticles are trapped by dendritic
surfaces of intermediate generation dendritic polymers, and/or are
retained by non-covalent conjugation with the interior scaffolding
of lower generation dendritic polymers, or are retained by
non-covalent conjugation with the exterior functional groups of
generally any generation of dendritic polymer.
[0064] The second step of the method involves transformation of the
nanosized inorganic reactant or reactants. Such transformation
include reactions involving two or more localized reactants, as
well as reactions involving transformation of a single reactant,
such as zero order decomposition reactions induced by chemical
instability, heat, electromagnetic radiation, etc.
[0065] After an appropriately selected chemical or physical
transformation into elements or compounds such as sulfides,
halogenides, oxides, hydroxides, phosphates, sulfates, hydroxides,
etc., these nanocomposites may preserve their chemical reactivity
and they can be transformed into other nanocomposites by subsequent
reactions. Also demonstrated is the ability of the nanocomposites
to undergo physical changes, such as crystallization and change of
their crystal morphology.
[0066] Lower generation dendritic polymers, e.g., 0 to generation 3
PAMAM dendrimers, typically are so open that they are incapable of
constraining a reaction product when they are dispersed in a gas or
liquid phase. However, when they are dispersed in a solid phase,
they are capable of constraining a reaction product and serve as a
template. These lower generation dendritic polymers may include
interior scaffolding groups, i.e., functional groups located nearer
to the core of the dendritic polymer than the exterior or surface
groups which are capable of activating non-covalent interactions
with a guest atom, ion or molecule, as well as exterior or surface
functional groups which are capable of achieving non-covalent
interactions with a guest atom, ion and/or molecule. As another
example, relatively higher generation dendrimers, such as
generation 7 PAMAM dendrimers and higher, may not be sufficiently
permeable to permit reactants to enter the interior of the
dendritic polymer. However, these higher generation dendritic
polymers may include exterior or surface functional groups capable
of achieving non-covalent interactions with guest atoms, ions,
and/or molecules. In the case of poly(arnidoamine) dendrimers,
generations 4 through 6 generally exhibit intermediate generation
properties because they have an interior which is accessible to a
wide variety of reactants of interest. Generation zero through 3
PAMAM dendrimers exhibit lower generation internal scaffolding
properties in which guest atoms, ions, and/or molecules may be
non-covalently conjugated to interior functional groups, but cannot
be contained within a well defined interior. Generation 7 and
higher PAMAM dendrimers exhibit higher generation properties
wherein guest atoms, ions, and/or molecules may not interact with
the interior thereof, but can become non-covalently conjugated to
surface groups thereof.
[0067] In accordance with one aspect of this invention there is
provided a method in which one or more molecules each of at least
one reactant is allowed to pass through a permeable surface of an
intermediate generation dendritic polymer and are reacted in an
interior of the dendritic polymer. The permeable surface allows
passage of the reactant or reactants. However, the surface is not
sufficiently permeable to allow passage of the reaction product,
thus trapping the product in the interior of the dendritic polymer.
The first step of the method involves localization of at least one
reactant within the interior of the dendritic polymer. Localization
within the dendritic polymer may be achieved by any mechanism which
allows the reactant or reactants to reside in the interior of the
dendritic polymer for a period sufficient to enable reaction of the
reactant or reactants to form a product which is larger than the
reactant or reactants and which is trapped within the dendritic
polymer. Localization includes physical restraint, whether
transient or relatively permanent, and non-covalent bonding with
the interior of the dendritic polymer. Examples of non-covalent
bonding between the reactant or reactants and the dendritic polymer
include ionic bonding, hydrogen bonding, donor-acceptor
interactions, coordinative bonding, Van der Waal interactions, and
London dispersion forces. The reactant or reactants are then
transformed into a reaction product which may be the product or two
or more reactants or the product of a single reactant, such as a
decomposition product. The reaction product formed is either
physically constrained relatively permanently within the interior
of the dendritic polymer molecule or is constrained within the
dendritic polymer molecule by non-covalent bonding with the
interior of the dendritic polymer molecule and immobilized with
respect to the polymer molecule.
[0068] This method can be used, for example, to solubilize
insoluble compounds. Thus among the types of unique composite
compositions contemplated by this invention are those in which a
nanosized dendritic polymer acts as a molecular vessel soluble in a
particular solvent, while the reaction product trapped within the
nanosized dendritic polymer molecular vessel is insoluble in that
solvent. In this manner, revolutionary products such as water-
soluble elemental metals, e.g., water-soluble copper, gold, silver,
water-soluble iron and cobolt, can be produced. This invention
contemplates water-soluble magnets. Other examples include
water-soluble silver halides and water-soluble metal sulfides.
[0069] In accordance with another aspect of the invention there is
provided a method in which one or more molecules each of at least
one reactant are localized with respect to the lower generation
dendritic polymer by contacting the reactant or reactants with a
lower generation dendritic polymer and allowing the reactant or
reactants to non-covalently interact with, and become
non-covalently conjugated to, interior scaffolding groups of the
lower generation dendritic polymer. The openness of the lower
generation dendritic polymers provides accessible interior
functional groups to which the reactant(s) can be non-covalently
conjugated, but does not allow physical constraint within a well
defined interior, without appropriately selected surface groups or
inclusion into a solid phase. Non-covalent conjugation or bonding
between the reactant or reactants and the internal scaffolding
groups of the lower generation dendritic polymers may include ionic
bonding, donor-acceptor interactions, coordination bonds, hydrogen
bonding, Van der Waal interactions, London dispersion interactions,
etc. As with the nanocomposites formed between the intermediate
generation dendritic polymers having a well defined surface and
interior, the conjugates, formed by interaction between the
internal scaffolding groups of lower generation dendritic polymers,
the localized inorganic reactant or reactants are transformed into
a reaction product which may be the product of two or more
reactants or the product of a single reactant, such as a
decomposition product.
[0070] In accordance with a further aspect of the invention, there
is provided a method in which one or more molecules each of at
least one reactant is localized with respect to a dendritic polymer
of generally any generation by contacting a dendritic polymer
having surface functional groups with the reactant or reactants and
allowing the reactant or reactants to non-covalently interact with,
and become non-covalently conjugated to, the exterior surface
functional groups of the dendritic polymer. Non-covalent conjugate
or bonding between the reactant or reactants and the exterior
surface functional groups of the dendritic polymer may include
ionic bonding, hydrogen bonding, Van der Waal interactions, London
dispersion interactions, donor-acceptor bonding, coordination
bonding, etc. The localized inorganic reactant or reactants are
subsequently transformed into a reaction product which may be the
product of two or more reactants or the product of a single
reactant, such as a decomposition product.
[0071] In the case of lower generation dendritic polymers having a
relatively open structure, without a well defined interior or
surface, an inorganic reactant or reactants may be localized by
interactions with interior scaffolding functional groups and/or
with exterior surface groups. In the case of intermediate
generation dendritic polymers, the reactant or reactants may be
localized by being constrained within the interior of the dendritic
polymer and/or localized by non-covalent interaction with exterior
functional groups and/or interior functional groups of the
dendritic polymer.
[0072] Another aspect of this invention relates to the distribution
of nanosized inorganic compounds in a polymeric matrix material.
Polymeric matrix materials include generally any polymer capable of
forming a continuous matrix phase of a composite material.
Polymeric matrix materials can contain the dendritic nanocomposites
in different ways, such as:
[0073] A. A chemical bond between the matrix and the dendritic
polymer. This usually involves a dendritic polymer bearing
polymerizable groups, such as amino methacrylate, OH, ester, etc.
(Amino groups readily interact) which is polymerized or
copolymerized with an other monomer; and
[0074] B. The dendritic nanocomposite physically dispersed such as
in a polymer, a solution of a polymer, a solution of a monomer, or
in a monomer followed by polymerization of the monomer.
[0075] The dispersed phase can be comprised of dendritic polymers
organized into zero, one, two or three dimensional structures, and
having the localized inorganic reaction products described herein
constrained within the interior of an intermediate generation
dendritic polymer, non-covalently conjugated to the interior
scaffolding functional groups of a lower generation dendritic
polymer, non-covalently conjugated to the exterior functional
groups of generally any generation dendritic polymer,
non-covalently conjugated to both interior scaffolding functional
groups and exterior surface groups of a lower generation dendritic
polymer, or both constrained within the interior of an intermediate
generation dendritic polymer and non-covalently conjugated to the
exterior surface functional groups of the intermediate generation
dendritic polymer. The invention also includes composite materials
in which the inorganic compound is distributed by physical methods
as discrete nanosized entities dispersed in a polymeric matrix, and
in which the dendritic polymers used to determine and control the
size and size distribution of the inorganic material are removed by
pyrolysis. Such composites are prepared by distributing the
dendritic nanocomposition comprising a dendritic polymer matrix and
subsequently subjecting the composite to an elevated temperature
for a sufficient period of time to cause the dendritic polymer to
decompose, preferably without causing any degradation of the matrix
material.
[0076] The dendritic polymer can be distributed in a polymeric
matrix either before the reactant or reactants are localized with
respect to the dendritic polymer, and either before or after the
reactant or reactants are transformed.
[0077] These organic-inorganic nanocomposites display new and
surprising properties.
[0078] Unstained transmission electron micrographs (TEM) show the
nanocomposites with a high contrast due to their metal content
(FIG. 3).
[0079] Hydrodynamic volumes of dendritic nanocomposites are
practically identical with their host as measured by size exclusion
chromatography (SEC) (FIG. 3A). Capillary electrophoresis (FIG. 3C)
and ion-pair HPLC on a reversed phase (FIG. 3B) indicates no or
minor changes in the surface properties and sizes of the hosts.
[0080] Their .sup.13C NMR spectra (see FIGS. 4A and 4B) show split
but narrow carbon signals suggesting that the metal atoms are
localized. Lines observed in .sup.1H NMR spectrum are generally
broad and show that all the proton signals are affected by the
presence of the metal atoms (FIG. 5). As most of the dendritic
polymers absorb only in the UV (see e.g., FIG. 6), these
nanocomposites generally display the characteristic color of the
inorganic component or the characteristic color of their plasmon
peak (FIG. 15). Dendritic nanocomposites in solution may undergo
clustering, depending on their surface properties. Dendritic
nanocomposite solutions often have a hazy appearance in a scattered
light (Tyndall-effect), while the same solution appears to be
transparent in transmitted light. Both phenomena are due to the
nanometer-scale size of the particles dispersed.
[0081] As a consequence of considerable increase in their density
with respect to the original dendritic polymer, solutions of
dendritic nanocomposites often exhibit accelerated sedimentation
without real precipitation. In the case of colored nanocomposites,
a visible concentration-gradient may be observed in the solution
due to the effect of the gravity.
[0082] Solubility of nanocomposites will be determined by the
solubility of the dendritic host rather than the solubility of the
guest compound or substance itself. Therefore, these dendritic
nanocomposites may be soluble either in water, and/or polar or
nonpolar organic solvents, depending on the solubility of their
host. These solutions may behave as real solutions, subcolloidal or
colloidal solutions in inorganic or organic solvents. Overall
solubility of these nanocomposites is many orders of magnitude
higher than would be expected from the solubility product of their
un-encapsulated form. Due to the extremely small size of the
inorganic component, a very high surface/mass ratio is established
for the guest atoms, ions and/or molecules which contributes to
their enhanced chemical activity.
[0083] In the preferred embodiment, the nanosized dendritic polymer
molecular reaction vessels have a preferred mean diameter range of
from about 10 to about 1,000 Angstroms, although they can be
larger. A more preferred mean diameter range is from about 10 to
about 600 Angstroms. Any of the dendritic polymers may be used.
Preferred dendritic polymers include dense star polymers and hyper
comb-branched polymers. The individual dendritic polymer
nanoreactors can be aggregated together through physical or
non-covalent interactions or covalent bonding to form larger,
multi-celled reaction vessels before or after being exposed to a
reactant. Suitable dendritic polymers include dendritic copolymers,
such as the reaction product of linear, branched or crosslinked
non-dendritic polymers with dendrimers, crosslinked dendrimers,
covalently linked dendrimer clusters, etc.
[0084] The surface of the intermediate generation dendritic polymer
molecular reaction vessel is relatively permeable to reactants, but
is relatively impermeable to reaction product. The term "permeable"
is intended to encompass composites in which the reactant may
diffuse out of the dendritic polymer molecule over time, but not
before the composite can be used for its intended purpose. Change
of permeability may result from the change in the relative density
of the surface groups (steric hindrance) or from the chemical
characteristics of the surface, such as relative hydrophilicity or
hydrophobicity or charge density.
[0085] The dendritic polymer does not have to be soluble, only
accessible by diffusion. The use of soluble dendritic polymers
however enables one to render normally insoluble compounds soluble
and tractable.
[0086] Suitable dendritic polymers include PAMAM dense star
polymers. Other preferred dendritic polymers include
polypropylamine (POPAM) dendrimers and polyester dendrimers.
[0087] An infinite variety of reactants can be employed in the
broader aspects of the invention. Especially preferred are
reactants which can react to yield elemental metals. Their use in
conjunction with soluble dendritic polymers leads to products such
as soluble magnets and homogenous phase catalytic solutions using
solvent soluble elemental metals.
[0088] The solvent dispersible products of the preferred embodiment
comprise a metal or metalloid (e.g., As, Sb, B, C, Ge, Po, P, Se,
Si, Te) compound, which is substantially insoluble in a solvent,
complexed with a dendritic polymer, which is soluble in the
solvent. The inorganic complexes are prepared by contacting a
solution containing the first reactant with the coordination
bonding sites of a dendritic polymer resulting in a complex or
coordination compound, and subsequently contacting this complex
with a reagent which reacts with the complexed compound to form a
composite that contains one or more immobilized compounds dispersed
on the nanoscale level, wherein the immobilized compound is
normally substantially insoluble in the solvent in the absence of
the dendritic polymer.
[0089] The dendritic polymers which may be used include generally
any of the known dendritic architectures including dendrimers,
regular dendrons, controlled hyperbranched polymers, dendrigrafts,
and random hyperbranched polymers. Deridritic polymers are polymers
with densely branched structures having a large number of reactive
groups. A dendritic polymer includes several layers or generations
of repeating units which all contain one or more branch points.
Dendritic polymers, including dendrimers and hyperbranched
polymers, are prepared by condensation reactions of monomeric units
having at least two reactive groups. The dendrimers which can be
used include those comprised of a plurality of dendrons that
emanate from a common core which can be a single atom or a group of
atoms. Each dendron generally consists of terminal surface groups,
interior branch junctures having branching functionalities greater
than or equal to two, and divalent connectors that covalently
connect neighboring branching junctures.
[0090] Dendrons and dendrimers can be prepared by convergent or
divergent synthesis.
[0091] Divergent synthesis of dendrons and dendrimers involves a
molecular growth process which occurs through a consecutive series
of geometrically progressive step-wise additions of branches upon
branches in a radially outward molecular direction to produce an
ordered arrangement of layered branched cells. Each dendritic
macromolecule includes a core cell, one or more layers of internal
cells, and an outer layer of surface cells, wherein each of the
cells includes a single branch juncture. The cells can be the same
or different in chemical structure and branching functionality. The
surface branch cells may contain either chemically reactive or
passive functional groups. Chemically reactive surface groups can
be used for further extension of dendritic growth or for
modification of dendritic molecular surfaces. The chemically
passive groups may be used to physically modified dendritic
surfaces, such as to adjust the ratio of hydrophobic to hydrophilic
terminals, and/or to improve the solubility of the dendritic
polymer for a particular solvent.
[0092] Convergent synthesis of dendrimers and dendrons involves a
growth process which begins from what will become the surface of
the dendron or dendrimer and progresses radially in a molecular
direction toward a focal point or core. The dendritic polymers may
be ideal or non-ideal, i.e., imperfect or defective. Imperfections
are normally a consequence of either incomplete chemical reactions,
or unavoidable competing side reactions. In practice, real
dendritic polymers are generally nonideal, i.e., contain certain
amounts of structural imperfections.
[0093] The hyperbranched polymers which may be used represent a
class of dendritic polymers which contain high levels of nonideal
irregular branching as compared with the more nearly perfect
regular structure of dendrons and dendrimers. Specifically,
hyperbranched polymers contain a relatively high number of
irregular branching areas in which not every repeat unit contains a
branch juncture. The preparation and characterization of
dendrimers, dendrons, random hyperbranched polymers, controlled
hyperbranched polymers, and dendrigrafts is well known. Examples of
dendimers and dendrons, and methods of synthesizing the same are
set forth in U.S. Pat. Nos. 4,507,466; 4,558,120; 4,568,737;
4,587,329; 4,631,337; 4,694,064; 4,713,975; 4,737,550; 4,871,779
and 4,857,599. Examples of hyperbranched polymers and methods of
preparing the same are set forth, for example in U.S. Pat. No.
5,418,301.
[0094] The dendritic polymers or macromolecules useful in the
practice of this invention are characterized by a relatively high
degree of branching, which is defined as the number average
fraction of branching groups per molecule, i.e., the ratio of
terminal groups plus branch groups to the total number of terminal
groups, branched groups and linear groups. For ideal dendrons and
dendrimers, the degree of branching is 1. For linear polymers, the
degree of branching is 0. Hyperbranched polymers have a degree of
branching which is intermediate that of linear polymers and ideal
dendrimers, a degree of branching of at least about 0.5 or higher
is preferred. The degree of branching is expressed as follows: 1 f
br = N t + N b N t + N b + N 1
[0095] where N.sub.x is the number of type x units in the
structure. Both terminal (type t) and branched (type b) units
contribute to the fully branched structure whilst linear (type 1)
units reduce the branching factor; hence 2 0 f br 1
[0096] where .function..sub.br=0 represents the case of a linear
polymer and .function..sub.br=1 represents the case of a fully
branched macromolecule.
[0097] Dendritic polymers suitable for use with the invention also
include macromolecules commonly referred to as cascade molecules,
arborols, arborescent grafted molecules, and the like. Suitable
dendritic polymers also include bridged dendritic polymers, i.e.,
dendritic macromolecules linked together either through surface
functional groups or through a linking molecule connecting surface
functional groups together, and dendritic polymer aggregates held
together by physical forces. Also included are spherical-shaped
dendritic polymers and rod-shaped dendritic polymers grown from a
polymeric core.
[0098] The dendritic polymers used in the practice of this
invention can be generationally monodisperse or generationally
polydisperse. Dendritic polymers in a monodisperse solution are
substantially all of the same generation, and hence of uniform size
and shape. The dendritic polymers in the polydisperse solution
comprise a distribution of different generation polymers. The
dendritic polymer molecules which may be used in the practice of
this invention include mixtures of different interior and exterior
compositions or functionalities. Examples of suitable dendritic
polymers include poly(ether) dendrons, dendrimers and hyperbranched
polymers, poly(ester) dendrons, dendrimers and hyperbranched
polymers, poly(thioether) dendrons, dendrimers and hyperbranched
polymers, and poly(arylalkylene ether) dendritic polymers.
Poly(amidoamine) (PAMAM) dendrimers have been found to be
particularly useful for preparing the metal-containing complexes of
this invention.
[0099] Dendritic polymers which are useful in the practice of this
invention include those that have symmetrical branch cells (arms of
equal length, e.g., PAMAM dendrimers) and those having
unsymmetrical branch cells (arms of unequal length, e.g.
lysine-branched dendrimers) branched dendrimers, cascade molecules,
arborols, and the like.
[0100] The term "dendritic polymer" also includes so-called "hyper
comb-branched" polymers. These comprise non-crosslinked
poly-branched polymers prepared by (1) forming a first set of
linear polymer branches by initiating the polymerization of a first
set of monomers which are either protected against or non-reactive
to branching and grafting, during polymerization, each of the
branches having a reactive end unit upon completion of
polymerization, the reactive end units being incapable of reacting
with each other; (2) grafting the branches to a core molecule or
core polymer having a plurality of reactive sites capable of
reacting, with the reactive end groups on the branches; (3) either
deprotecting or activating a plurality of monomeric units on each
of the branches to create reactive sites; (4) separately forming a
second set of linear polymer branches by repeating step (1) with a
second set of monomers; (5) attaching the second set of branches to
the first set of branches by reacting the reactive end groups of
the second set of branches with the reactive sites on the first set
of branches, and then repeating steps (3), (4) and (5) above to add
one or more subsequent sets of branches. Such hyper comb-branched
polymers are disclosed in European Patent Publication 0473088A2. A
representative formula for such hyper comb-branched polymer is:
1
[0101] wherein C is a core molecule; each R is the residual moiety
of an initiator selected from a group consisting of free radical
initiators, cationic initiators, anionic initiators, coordination
polymerization initiators and group transfer initiators; A and B
are polymerizable monomers or comonomers capable of withstanding
the conditions required for branching therefrom or grafting
thereto, at least during the polymerization of the {(A)-(B)} linear
polymer chain and during its grafting to a prior {(A)-(B)} branch
of the {(A)-(B)} core branch; each G is a grafting component, and
the designation
[0102] G--{(A).sub.(1-y)-(B).sub.y}
[0103] indicates that G can attach to either an (A) unit or a (B)
unit; n is the degree of polymerization of the indicated generation
comb-branches; y is the fraction of B units in the indicated
generation branch, and has a value of 0.01 to 1; the superscripts
0, 1 and i designate the comb-branch generation level, with i
beginning at "2" and continuing for the number of reiterative
branch set generations in the polymer; and at least n.sup.0 and
n.sup.1 are .gtoreq.2.
[0104] For purposes of clarifying terminology, it should be noted
that dense star dendrimers are built by reiterative terminal
branching, while hyper comb-branched dendrimers are built by
reiterative comb-branching. In dense star dendrimers, subsequent
generation branches are attached to the terminal moieties of a
previous generation, thus limiting the degree of branching to the
functionality of the previous generation terminal moiety, which
would typically be two or three. In contrast, by branching
oligomers upon prior generation oligomer branches in accordance
with hyper comb-branched dendrimer, one can dramatically increase
the degree of branching from generation to generation, and indeed
can vary the degree of branching from generation to generation.
[0105] Dendritic polymers, especially dendrimers, may contain
coordination moieties or binding sites which are capable of
non-covalently bonding with metals and or metal-containing
compounds to complex with and localize such metals,
metal-containing compounds or metalloid-containing compounds within
the dendritic polymer. For example, PAMAM dendrimers possess both
tertiary amines and amide groups which are present according to
mathematically driven dendritic rules. In addition to internal
complexation, diffusion resistance towards the surface of the
dendrimer increases for any guest molecule or compound due to the
radially increasing density of the dendrimer interior. This
resistance also increases with the number of generations and
provides a diffusion barrier which helps keep complexed molecules
or atoms inside the dendrimer. Accordingly, higher generation
dendrimers, such as fourth and higher generation dendrimers, are
preferred for the PAMAM family of dendrimers in solution.
[0106] The metal ion solutions which may be contacted with a
dendritic polymer to form the metal-containing complexes of this
invention include inorganic salt solutions in which the metal or
metal-containing compounds are present as soluble ions. When such
inorganic salt solutions are mixed with dendritic polymers, the
metal ions or metal-containing ions diffuse to the dendritic
polymer and interact with available binding sites and become
complexed by the dendritic polymer, or by a solvent contained
within the interior of the dendritic polymer. The solvent, such as
water, contained within the dendritic polymer can be different from
the solvent in which the outer surface of the dendrimer is
dissolved. Depending on the internal architecture, and the number,
quality and density of the surface functional groups, complexation
may take place in the interior only, or both in the interior and on
the exterior of the dendritic polymer. The high local concentration
of covalently connected coordination binding sites in the dendritic
polymers and the diffusion barrier at the surface of the dendritic
polymers enables these molecules to immobilize and retain
compounds. Dendritic polymers with internal binding sites can be
regarded as nanosized organic containers and/or nanosized reactors.
Because the retained compounds are not covalently bonded to the
dendritic polymer, they can undergo chemical reactions in
accordance with their nature and reactivity.
[0107] Examples of suitable inorganic salt solutions which can be
contacted with dendritic polymers to form metal-containing
complexes include metal acetates such a cadmium acetate, copper
acetate, zinc acetate, and lead acetate; metal sulfates, such as
iron sulfate; and metal trifluoromethanesulfonates, such as silver
trifluoromethanesulfonat- e. Other examples are set forth in the
Experimental Section below.
[0108] The soluble metal-containing ion solution is contacted with
a dendritic polymer to form a metal-dendritic polymer complex. The
dendritic polymer is preferably solubilized in or swelled with a
solvent prior to combining with the soluble metal-containing ion
solution. The metal-dendritic polymer complex is subsequently
contacted with a reagent which reacts with the complexed metal
compound to form a different metal compound which is substantially
insoluble in the absence of the dendritic polymer. For example, any
of various complexes formed by combining metal-acetates with a
dendritic polymer may be reacted with hydrogen sulfide to form
metal sulfide/dendritic polymer composites which are highly
soluble, as opposed to the metal sulfides which are insoluble in
most liquids such as water and organic solvents. As another
example, a silver trifluoromethanesulfonate-dendritic polymer
complex [CF.sub.3SO.sub.3Ag-D] can be reacted with hydrogen sulfide
gas to produce a silver sulfide/dendritic polymer composite which
is soluble in water and/or organic solvents. An iron sulfate
(FeSO.sub.4)/dendritic polymer complex can be reacted with hydrogen
sulfide gas to form an iron sulfide/dendritic polymer complex which
is soluble in water and/or a variety of organic solvents. Examples
of various metal sulfide, metal halogenide, metal hydroxide, metal
oxalate, metal phosphate, and elemental metal contained within a
soluble dendritic polymer are set forth in the examples below.
[0109] The complexation of metal-containing compounds combined with
the dendritic diffusion barrier create single/individual organic
containers/reactors having sizes in the range of from about 10 to
about 200 Angstroms, depending upon the generation of the dendritic
polymer and the particular structure and family of dendritic
polymer used. Among other parameters, such as solvent, temperature,
dendrimer type and generation, capacity of the nanoreactors will
depend on the nature, number, quality and position of the
coordination moieties or binding sites. Insoluble compounds can be
immobilized and at the same time solubilized according to the
solubility of the dendritic polymer host, rather than the
solubility of the metal or substance itself. During this
immobilization, atoms, ions and molecules become trapped in the
polymer due to the combined effect of the complexation and the
dendritic diffusion barrier. Thus, compounds which are commonly
regarded as being insoluble, such as metal sulfides, halogenides,
sulfates, phosphates, oxalates, etc., and metals themselves, can
behave as real solutions in water as stable subcolloid solutions in
organic solvents.
[0110] The metal compound concentration of these solutions can be
many orders of magnitude higher than expected from the
non-encapsulated solubility product of the metal compound in water
or organic solvents. As a consequence, the metal-loaded dendritic
containers display new and surprising properties. Dendrimer
encapsulated compounds may enter chemical reactions without
precipitation from the solvents in which they are dispersed.
[0111] Furthermore, the dendritic surface may be chemically
modified without closing the dendrimer surface, preserving
permeability and for fine-tuning the nanocomposite formation. For
example, hydroxyl, carboxyl, or amine-terminated dendritic polymers
can be reacted with an epoxy-terminated alkane, such as
1,2-epoxydecane, to form a dendritic polymer having a hydrophobic
surface. Thus, the surface of the dendritic polymer of the
metal-containing compound/dendritic polymer complex can be modified
as desired to facilitate solubility of the complex in non-polar
organic solvents, including alkyl and aromatic solvents.
Alternatively, the surface of the dendritic polymer can be provided
with functional groups, such as hydroxyl, carboxyl or amine groups,
which facilitate solubility of the complex in water and/or polar
organic solvents, such as alcohols. Using difunctional reactants it
is possible to attach a polymerizable group to the surface of the
dendritic polymer, or crosslink the dendritic polymer.
Practical Use
[0112] This method extends the potential use of numerous inorganic
materials and compounds (such as sulfides, halogenides, sulfates,
and other chemical entities) to applications which were not
previously possible because of the overall insolubility (see Table
I) or intractability of such substances. The method also makes it
possible to synthesize revolutionally new chemical entities, which
were not available before, by employing molecular size scaffolds
with well defined and exactly known structure as nanoreactors and
use the same nanoreactors as containers or templates with
chemically reactive surfaces for the atomic level dispersion of the
components additional to the dendritic polymers in the composites.
For example, the inventors have discovered that extremely small
magnets can be prepared which do not exhibit any hysteresis, that
is the material's magnetic properties do not change when a magnetic
field is repeatedly applied to it.
[0113] These dendritic nanocomposites may be further transformed
into clusters, gels, networks and other useful macromolecular
structures. Dendritic polymer encapsulated nanocomposites thus
obtained will have useful chemical, catalytic, magnetic, optical,
electrically conductive, photolytic and electroactive properties.
These "nanoencapsulated" or "nanotemplated" compounds may enter
into selective chemical reactions without precipitating from their
host. Also, subsequent chemical transformation of the outer surface
of a dendritic polymer nanocomposite may transform a soluble
nanocomposite into an insoluble one, thus providing an effective
way for selective removal of poisonous metals or metal-containing
compounds from solvents. Solutions containing dendritic polymer
composites may provide novel optical filters. Chemical coding with
dendritic markers having any of various well defined ratios of
different metals immobilized in the interior of a dendritic
molecule can be used to tag various materials such as
explosives.
[0114] It is envisioned that dendritic nanocomposites will have
many uses including selective extraction, and selective
drug-delivery to particular biological targets.
[0115] The invention will be described in further detail by
reference to examples of metal sulfides, which are useful as
semiconductors and magnetic resonance imaging agents and with
reference to light and electromagnetic radiation sensitive silver
salts, which are useful as photochemical reactants.
EXPERIMENTAL
[0116] To simplify the description of compounds, braces were used
to indicate the nanocomposite structure while naming the inorganic
component and sometimes the organic component within the braces.
Thus, symbols, such as {Cu(OH).sub.2} and {CuOH-G4.T}, denote a
nanocomposite which contains copper(II) hydroxide and a composite
formed of CuOH and a PAMAM generation four, tris-modified (G4.T)
dendrimer, respectively. Double underline denotes formation of a
macroscopic precipitate (e.g., CuS) and brackets, such as
[Cu(NH.sub.3).sub.4]OH, indicate a complex compound.
[0117] The following experiments demonstrate and prove our concept
without restricting the possibilities to the existing examples or
limiting the area of other possible chemical transformations:
Example Group I
[0118] Preparation of copper containing nanocomposites.
Example Group II
[0119] Formation of metal sulfide solutions in water.
Example Group III
[0120] Preparation of AgOH, AgBr, AgCl, silver and gold
nanocomposites.
Example Group IV
[0121] Preparation of methanolic silver bromide solution.
Example Group V
[0122] Preparation of copper sulfide solution in toluene.
Example Group VI
[0123] Comparison of sulfide nanocomposite formation in Astramol
and Perstorp dendritic hosts.
Example Group VII
[0124] Preparation of magnetic dendritic nanocomposites using
aqueous solutions of zero valence metals.
Example Group VIII
[0125] Preparation of miscellaneous water soluble dendritic
nanocomposites.
Example Group IX
[0126] Preparation of miscellaneous insoluble dendritic
nanocomposites and films.
Reagents Used In The Following Examples:
[0127] 10 mM solutions of AgCF.sub.3SO.sub.3,
Bi(CH.sub.3COO).sub.3, Cd(CH.sub.3COO).sub.2.times.2 H.sub.2O,
Cu(CH.sub.3COO).sub.2, x H.sub.2O, CaCl.sub.2, CoCl.sub.2,
Pb(CH.sub.3COO).sub.2.times.3 H.sub.2O, FeSO.sub.4, FeCl.sub.3,
Zn(CH.sub.3COO).sub.2, HAuCl.sub.4, Mn(CH.sub.3COO).sub.2.times.4
H.sub.2O, oxalic acid
[0128] H.sub.2S gas, cc NH.sub.4OH and glacial acetic acid, 100 mM
solutions of CaCl.sub.2, NaOH, NaCl, NaI, and KBr, ascorbic acid,
ethylenediaminetetraacetic acid disodium salt,
(POLYAMIDOAMINE) PAMAM-s
[0129] 1.0 ml of 1.0 mM solutions (1.0.times.10.sup.-6 mole)
of:
[0130] generation four (EDA core) PAMAM containing 64-NH.sub.2
surface group and 124 internal ligands (tert-nitrogens and NH-CO
groups) (G4.0), see Table II;
[0131] generation four (EDA core) Tris-modified PAMAM dendrimer
containing 192 primary aliphatic hydroxyl group as surface groups
and 124 internal ligands (tert-nitrogens and NH-CO groups)
(G4.T);
[0132] generation four (EDA core) full generation pivaloyl-modified
PAMAM dendrimer containing 128 tert-butyl group as surface groups
and 256+128=384 internal ligands (tert-nitrogens and NH-CO groups)
(G5.P);
[0133] generation four (EDA core) full generation
ethanolamine-modified PAMAM dendrimer containing 128 aliphatic OH
group as surface groups and 256 internal ligands (tert-nitrogens
and NH-CO groups) (G5.OH);
[0134] generation three to seven (EDA core) Tris-modified PAMAM
dendrimer containing primary aliphatic hydroxides as surface groups
and variable number of internal ligands (tert-nitrogens and NH-CO
groups) as it is described in Table II;
[0135] 1.43 mM solution of generation four (NH.sub.3 core) PAMAM
modified by 1,2-epoxydecane (G4.EO10; hydrophobic surface).
1TABLE II Change of number of ligands in the EDA core PAMAM
generations Number of Number of Internal Surface Measured
Generation Ligands NH.sub.2 Groups MW Diameter G2.0 28 16 3,256 29
.ANG. G3.0 60 32 6,909 36 .ANG. G4.0 124 64 14,215 45 .ANG. G5.0
252 128 28,826 54 .ANG. G6.0 508 256 58,048 67 .ANG. G7.0 1020 512
116,493 81 .ANG. G8.0 2044 1024 233,383 97 .ANG. G9.0 4092 2048
467,162 114 .ANG. G10.0 8188 4096 934,720 135 .ANG.
[0136]
2TABLE III Change of number of ligands in EDA core, tris-modified
PAMAMs Number of Number of PAMAM Internal Surface OH Dendrimer
Ligands Groups MW G2.T 28 48 4,233 G3.T 60 96 8,863 G4.T 124 192
18,636 G5.T 252 384 36,644 G6.T 508 768 73,685 G7.T 1020 1536
147,765
ASTRAMOL.TM. (Polypropylenamine) dendrimers:
[0137] 1 mM solution of generation four polypropylenamine dendrimer
(AM-4, DAB(PA).sub.64, FW=7,168; r.sub.G=13.9 .ANG., containing 64
NH.sub.2 group on the surface) in methanol.
3TABLE IV ASTRAMOL .TM. (Polypropylenamine) dendrimers: Number of
Number of Internal Surface Measured Name Ligands Groups MW Diameter
G1 = DAB(CN).sub.8 6 8 741 12 .ANG. G1 = DAB(PA).sub.8 6 8 773 13.8
.ANG. G2 = DAB(CN).sub.16 14 16 1,622 16 .ANG. G2 = DAB(PA).sub.16
14 16 1,687 18.6 .ANG. G3 = DAB(CN).sub.32 30 32 3,385 20.2 .ANG.
G3 = DAB(PA).sub.32 30 32 3,514 23.2 .ANG. G4 = DAB(CN).sub.8 62 64
6,910 24.4 .ANG. G4 = DAB(PA).sub.64 62 64 7,168 27.8 .ANG.
PERSTORP.TM.(Hyperbranched Polyesters):
[0138] 1 mM methanol solution of generation five hyperbranched
polyester (PSG5, F.sub.w.sub..sub.theor=14,754, containing 128 OH
groups on the surface);
[0139] The ratio of metal ions to the dendritic macromolecules was
based on the general assumption that a metal ion would be
coordinated by four tertiary nitrogens and/or NHCO amide groups or
by two surface-NH.sub.2 amino groups of the given dendrimer. Of
course, actual coordination numbers are function of many
parameters. All experiments were performed at room temperature,
unless otherwise noted.
Examples
[0140] We demonstrate our concept on the examples of insoluble
metal sulfides (see also the enclosed solubility data) and silver
halides. Miscellaneous examples of different type nanocomposites
are also included.
[0141] To illustrate several unique features of our invention, the
formation of copper- dendrimer internal complex and
copper-containing dendritic nanocomposites are described first. As
a typical representative, a generation four (EDA core)
tris(hydroxymethyl)aminometh- ane-modified PAMAM dendrimer was used
containing 192 primary aliphatic hydroxide groups as surface end
groups (G4.T).
Example Group I
Preparation of Copper-containing Nanocomposites
[0142] In this collection of examples [Cu(CH.sub.3COO).sub.2-PAMAM
G4.T] complex is used to demonstrate the subsequent formation of
copper nanocomposites.
Example Cu#1
Preparation of [Cu(CH.sub.3COO).sub.2-PAMAM G4.T]
[0143] In a 125 ml volume Pyrex absorption vessel, 0.362 g (2.0 x
10.sup.-5 mole) PAMAM G4.T dendrimer was dissolved in 40 ml
deionized water. To this solution was added 0.123 g
(6.19.times.10.sup.-4 mole) Cu(CH.sub.3COO).sub.2.times.X H.sub.2O
dissolved in 20 ml water. The light blue color of the
Cu(CH.sub.3COO).sub.2 solution instantaneously turned into deep
blue indicating the formation of the copper-dendrimer complex. The
reactor was purged with a slow stream of dry nitrogen for 10 min.
to ensure the perfect mixing. During this time an internal copper
complex of the dendrimer forms. This internal complex can be
isolated in solid form as a deep blue compound.
Of Isolating The Copper Ion-Dendrimer Complex
[0144] The solution of internal complex was transferred into a 250
ml round bottom flask and the solvent was evaporated on a rotavap
at 40.degree. C. yielding a deep blue solid layer
[Cu(CH.sub.3COO).sub.2 G4.T] on the wall. In contrast to the
inorganic copper salt this material readily dissolves in methanol
with a deep blue color. Thus, using 5 ml of methanol as a solvent,
the product was transferred into a glass vial and the solvent was
evaporated by applying a gentle nitrogen stream by means of a
Pasteur-pipet onto the surface of the solution. Further drying of
the product under vacuo at room temperature yielded 0.479 g (98%)
internal complex as a blue solid. Although on the reverse phase
ion-pair HPLC chromatogram (RP-IP HPLC, see FIG. 5) a copper-peak
can also be identified in addition to the peak of the composite,
even though the solubility in organic solvents, the
thermogravimetric analysis (TGA) thermograms and differential
scanning calorimetry (DSC) curves are different from those of the
starting materials.
[0145] Due to the very strong internal interactions between copper
and the array of ligands in the interior of this dendrimer, only a
partial separation of copper and copper-containing dendrimer can be
achieved by dialysis because the dendrimer container will be highly
favored by the copper ion. Table V illustrates the results of a set
of exhaustive dialysis experiments using semi-permeable 10 K
membranes, in which 3 ml of G4.0 and G4.T PAMAM dendrimer solutions
containing varying amounts of Cu.sup.2+ were dialysed against
3.times.300 mL deionized water for 3.times.2 days.
4TABLE V Comparison of Cu.sup.2+ Concentration Before and After
Dialysis. (Sample volumes before experiment: 3 ml; after
experiment: 3.5 ml in the case of G4.T, and 5.1 ml when G4.0 was
used. Dendrimer concentrations are identical, it is 8.84 .times.
10.sup.-5 M in each case, average Cu.sup.2+ concentrations were
measured by atomic absorption spectroscopy (AA)). [Cu.sup.2+
[Cu.sup.2+] after [Cu.sup.2+] after before dialysis dialysis (found
dialysis (found (calcd.) in the outside of the 10.sup.3 .times.
dendrimer) dendrimer) Name [mg/L] M [mg/L] 10.sup.4 .times. M
[mg/L] 10.sup.5 .times. M Cu.sup.2+-G4.T 115 1.81 26 4.09 0.28 0.36
Cu.sup.2+-G4.T 173 2.72 27 4.25 0.43 0.68 Cu.sup.2+-G4.T 288 4.53
27 4.25 0.64 1.01 Cu.sup.2+-G4.T 433 6.81 29 4.56 0.96 1.51
Cu.sup.2+-G4.T 577 9.08 37 5.82 1.22 1.92 Cu.sup.2+-G4.0 115 1.81
11 1.73 0.22 0.35 Cu.sup.2+-G4.0 173 2.72 10 1.57 0.48 0.76
Cu.sup.2+-G4.0 288 4.53 13 2.04 0.71 1.12 Cu.sup.2+-G4.0 433 6.81
10 1.57 1.13 1.78 Cu.sup.2+-G4.0 577 9.08 12 1.89 1.23 1.93
[0146] The results show that despite of the hundred-fold excess of
the dialysing water, the concentration of copper ions is at least
an order of magnitude higher inside of the dendrimers than outside.
Concentrations of copper inside of the semi-permeable membrane are
practically identical regardless [Cu].sub.0, and the value of these
final concentrations depend on the composition and architecture of
the dendrimer used. However, as it is demonstrated by reversed
phase ion-pair chromatography, this complex will display separate
peaks for copper ions and the dendrimer, illustrating the temporary
nature of the internal complex.
[0147] The above-described [Cu(CH.sub.3COO).sub.2-PAMAM G4.T]
internal complex was used to prepare different other
copper-containing composites by subsequent chemical transformations
to illustrate the synthesis of said novel nanocomposites with
surprising properties.
Example Cu#2
Preparation of {Cu(OH).sub.2-PAMAM G4.T} Nanocomposite:
[0148] [Cu(CH.sub.3COO).sub.2-PAMAM G4.T] inorganic-dendrimer
internal complex was prepared by mixing 1.0 ml of 1.0 mM solution
(1.0.times.10.sup.-6 mole) of G4.T and 3.1 ml of 10 mM aqueous
Cu(CH.sub.3COO).sub.2 solution (3.1.times.10.sup.-5 mole). In the
resulting solution the concentrations are: [Cu]
=7.56.times.10.sup.-6 M and [G4.T] 2.44.times.10.sup.-7 M, the
ligand/metal ion ratio is 4/1 and the metal ion/dendrimer molar
ratio =31/1.
[Cu(CH.sub.3COO).sub.2-G4.T].
[0149] To this solution, a high excess (4 ml) of 0.1 M NaOH
solution was added. The product solution retained its dark blue
color without any precipitation.
[Cu(CH.sub.3COO).sub.2-G4.T]+2 NaOH={Cu(OH).sub.2-G4.T}+2
CH.sub.3COONa
[0150] In contrast to this experiment, when the
Cu(CH.sub.3COO).sub.2 solution was used without encapsulation, a
flaky greenish-blue precipitate, Cu(OH).sub.2 was observed, that
subsequently turned into brown and then black as a consequence of
the dehydration of the copper(II) hydroxide.
Cu(CH.sub.3COO).sub.2+2 NaOH=Cu(OH).sub.2+2
CH.sub.3COONa=>CuO+H.sub.2O
[0151] greenish blue brown
Example Cu#3
Preparation of {Cu.sub.2O-G4.T} Nanocomposite:
[0152] [Cu(CH.sub.3COO).sub.2-PAMAM G4.T] inorganic-dendrimer
internal complex was prepared by mixing 1.0 ml of 1.0 mM solution
(1.0.times.10-6 mole) of G4.T and 3.1 ml of 10 mM aqueous
Cu(CH.sub.3COO).sub.2 solution (3.1.times.10.sup.-5 mole). In the
resulting solution the concentrations are: [Cu]
=7.56.times.10.sup.-6 M and [G4.T] =2.44.times.10.sup.-7 M, the
ligand/metal ion ratio is 4/1 and the metal ion/dendrimer molar
ratio =31/1.
[0153] [Cu(CH.sub.3COO).sub.2-G4.T].
[0154] To this solution 1 ml of 0.1 M NaOH solution was added. The
product solution {Cu(OH).sub.2-G4.T} retained its dark blue color
without any precipitation. To this solution 1 ml of 0.1 M ascorbic
acid (C.sub.6H.sub.8O.sub.6) solution was added. The solution
turned green, then yellow, indicating the formation of the
dendrimer encapsulated CuOH and Cu.sub.2O, respectively, but no
precipitation occurred.
{2 Cu(OH).sub.2}+C.sub.6H.sub.8O.sub.6=>{2 CuOH}+2 H.sub.2O
+C.sub.6H.sub.6O.sub.6
[0155] deep blue light green
{2 CuOH} =>{Cu.sub.2O}+H.sub.2O
[0156] light green yellow
[0157] The scattered light of this solution displays the yellow
color of the copper(I) oxide, while the solution remains
transparent and light blue in front of a white light source because
of the observation of the complementer color in transmitted light.
Due to the small size of the copper(I) oxide particles dispersed in
the dendrimer interior, the solution behaves as an optical
filter.
Example Cu#4
Preparation of {CuS-PAMAM G4.T} Composite
[0158] [Cu(CH.sub.3COO).sub.2-PAMAM G4.T] inorganic-dendrimer
internal complex was prepared using the procedure described in
Example Cu#1. Instead of isolating the copper ion--dendrimer
complex, a slow stream of hydrogen sulfide was bubbled through the
complex solution. The solution turned dark brown, but no
macroscopic precipitation was observed.
H.sub.2S+[Cu(CH.sub.3COO).sub.2-G4.T]={CuS -G4.T}+2CH.sub.3COOH
[0159] Addition of H.sub.2S was continued until the formation of a
white precipitate (ZnS) was observed in the gas washing tower
filled with 0.2 M solution of Zn(CH.sub.3COO).sub.2 which was used
as a decontaminator solution. Then the stream of H.sub.2S was
stopped, and the reactor was immediately purged with nitrogen for
30 mins. to remove the excess of H.sub.2S. The solution was
transferred into a 250 ml round bottom flask and the solvent was
evaporated on a rotavap at 40.degree. C. yielding a dark brown
solid layer {CuS-G4.T} on the wall. This material readily dissolves
in water with a dark brown color. The product was scraped from the
wall and the black solid was transferred into a glass vial. Further
drying of the product under vacuo at room temperature yielded 0.49
g (97%) of the nanocomposite as a black solid.
Example Cu#5
Preparation of {Cu.sub.2S-PAMAM G4.T} Composite:
[0160] [Cu(CH.sub.3COO).sub.2-PAMAM G4.T] inorganic-dendrimer
internal complex was prepared using the procedure described in
Example Cu#1. Instead of isolating the copper ion--dendrimer
complex, a slow stream of hydrogen sulfide was bubbled through the
solution. The solution turned dark brown, but no macroscopic
precipitation was observed.
H.sub.2S+[Cu(CH.sub.3COO).sub.2-G4.T]={CuS-G4.T}+2 CH.sub.3COOH
[0161] deep blue dark brown
[0162] Addition of H.sub.2S was continued until the formation of a
white precipitate (ZnS) was observed in the gas washing tower
filled with 0.2 M solution of Zn(CH.sub.3COO).sub.2 which was used
as a decontaminator solution. Then the stream was stopped and the
reactor was closed for overnight. After 16 hour reaction time, the
reaction mixture turned to dark green indicating a redox reaction
with the excess of hydrogen sulfide with the {CuS-G4.T}
nanocomposite.
S+2H.sup.++2e=H.sub.2S(g)
E.degree.=0.141 V
H.sub.2S+{2 CuS-G4.T}={Cu.sub.2S-G4.T}+2S+2 H.sup.+
[0163] dark brown dark green
[0164] This second reaction does not take place without
nanocomposite formation because CuS immediately precipitates from
water due to its extremely low solubility, See Table I.
[0165] The reaction flask was purged with nitrogen to remove the
residual H.sub.2S and then the sulphur was removed by a 0.45
microns Teflon syringe filter. The solution was transferred into a
250 ml round bottom flask and the solvent was evaporated on a
rotavap at 40.degree. C. yielding a dark green rigid layer of
{Cu.sub.2S-G4.T} on the wall. This material readily dissolves in
water forming a dark green color solution. The product was scraped
from the wall and the black solid was transferred into a glass
vial. Further drying of the product under vacuo at room temperature
yielded 0.49 g (97%) of the nanocomposite as a black solid.
Example Cu#6
Preparation of {Cu(O)-G5.P}Nanocomposite
[0166] [Cu(CH.sub.3COO).sub.2-PAMAM G5.P] inorganic-dendrimer
internal complex was prepared by mixing 1.0 ml of 1.0 mM methanol
solution (1.0.times.10.sup.-6 mole) of G5.P and 3.1 ml of 10 mM
aqueous Cu(CH.sub.3COO).sub.2 solution (3.1.times.10.sup.-5 mole).
In the resulting solution the concentrations are:
[Cu]=7.56.times.10.sup.-6 M and [G5.P]=2.44.times.10.sup.-7 M, the
ligand/metal ion ratio is 4/1 and the metal ion/dendrimer molar
ratio =31/1.
[0167] [Cu(CH.sub.3COO).sub.2-G5 .P].
[0168] To this solution 1 ml of 0.1 M ascorbic acid was added. The
solution changed its color to green, then, after a short induction
period, the solution displayed the characteristic color of metallic
copper, indicating the total reduction of nanoencapsulated
Cu.sup.2+ first into Cu.sup.+ and then Cu(O), respectively.
C.sub.6H.sub.8O.sub.6=C.sub.6H.sub.6O.sub.6+2 H.sup.++2e
[Cu(OAc).sub.2-G5.P]+C.sub.6H.sub.8O.sub.6=>{CuOAc-G5.P}+2H.sub.2O+C.su-
b.6H.sub.6O.sub.6
[0169] deep blue light green
[CuOAc-G5.P]+2H.sup.++2e=>{Cu(O)-G5.P}+H.sub.2O
[0170] light green metallic red
[0171] In scattered light, this solution displays the color of the
metallic copper while it remains transparent in transmitted light
because of the very small size of the copper particles dispersed in
the dendrimer interior (Tyndall-effect).
Example Group II
Formation of Metal Sulfide Solutions In Water.
[0172] A large number of examples can be used to demonstrate the
principle of our invention by utilizing the well-known experiments
of classical qualitative inorganic analysis. During the many years
of development, these observations have placed into analytical
classes. Hence, many reactions were defined as characteristic to
particular metal ions. These reactions have easily observable
features, such as intensive color change or formation of insoluble
precipitates under certain conditions. In the first two classes of
the classical qualitative inorganic analysis, reactions with
sulfide ions are utilized. However, in the presence of dendritic
polymers these reactions give surprising results.
[0173] General Description Of Procedure A:
[0174] 1) Internal Complex Formation:
[0175] Into a 14.8 ml screw-cap glass vial 1.0 ml of 1.0 mM
(1.0.times.10.sup.-6 mole) aqueous solution of generation four (EDA
core) tris-modified PAMAM dendrimer (G4.T) was added. (When it was
necessary, the pH was adjusted between pH=3 and pH 6 with glacial
acetic acid to prevent subsequent precipitation of the insoluble
metal hydroxide before the formation of the internal complex). To
this solution, 3.1 ml of 10 mM (3.1.times.1.sup.-5 mole) aqueous
metal ion solution was added. Dry nitrogen gas was bubbled through
the liquid to mix the two solutions and to remove air (removal of
the air prevents unwanted oxidation that may occur during the
consecutive steps). A typically 1 hour "rest period" was provided
to reach the equilibrium state of the metal ion complexation. In
this reaction mixture [M]=7.56.times.10.sup.-6 M and
[G4.T]=2.44.times.10.sup.-7 M, the ligand/metal ion ratio is 4/1
and the metal-ion/dendrimer molar ratio =31/1.
[0176] 2) Chemical Transformation:
[0177] In the next step, hydrogen sulfide gas was introduced in
excess into the reaction mixture to react with the metal ions.
Color changes indicated the formation of metal sulfides. The
H.sub.2S was bubbled through for 30 sec., then the vial was capped
and sealed with parafilm and left for overnight at room
temperature. After the reaction was completed, the samples were
sonicated for 30 min. and purged with nitrogen to remove the excess
of H.sub.2S. The samples were filtered through a 0.45 microns pore
size Teflon syringe filter to remove any macroscopic precipitates.
The samples were stored in solution at room temperature under
nitrogen.
[0178] As a general observation, color changes may occur during
mixing of the dendrimer and metal ion solution indicating complex
formation. Metal ion solutions without dendrimers gave insoluble
sulfides that precipitated quickly up addition of H.sub.2S, while
in the presence of dendritic hosts, colored but transparent
solutions formed. The color change indicates metal sulfide
formation, but no precipitation was observed in the presence of
appropriately selected dendritic polymers.
[0179] General Description Of Procedure B:
[0180] Same as Procedure A, except that 1.0 ml of 1.0 mM
(1.0.times.10.sup.-6 mole) aqueous solution of generation four (EDA
core) amine-terminated (G4.0) PAMAM dendrimer was added (see Table
II). The pH was adjusted with glacial acetic acid to be between
pH=3 and pH=6 to prevent subsequent precipitation of the metal
hydroxide. To this solution, 4.7 ml of 10 mM (4.7.times.10.sup.-5
mole) aqueous metal ion solution was added. In this reaction
mixture, [M]=8.25.times.1.sup.-6 M and [G4.T]=2.44.times.10.sup.-7
M, the ligand/metal ion ratio is 4/1 and the metal-ion/dendrimer
molar ratio =47/1. (M-G4.0).
[0181] When the dendrimers have complex forming ligands also as
their surface groups, the H.sub.2S reaction gave colored and hazy
solutions without any macroscopic precipitation. The haziness
indicated that metal ions that had not been immobilized in the form
of a nanocomposite coagulate when transformed into sulfides. These
particles were removed from the solution by filtration, resulting
in a clear solution of copper sulfide nanocomposite.
Example IIa
Preparation of {Cu.sub.2S} Composite Using Tris-modified PAMAMs
From Generation 3 to Generation 7
[0182] Procedure A was used. Calculated amounts of 10 mM aqueous
Cu(CH.sub.3COO).sub.2 solution were added to various dendrimer
solutions to keep the copper/ligand ratio equal to 4. A one-hour
"rest period" was provided.
[0183] Four Aqueous Solutions Were Prepared
[0184] (a) 5 ml 10 mM Cu(CH.sub.3COO).sub.2 solution,
[0185] (b) 5 ml 10 mM Cu(CH.sub.3COO).sub.2 solution plus 2 ml cc.
ammonium hydroxide (coordination provided by the NH.sub.3), i.e.,
[Cu(NH.sub.3).sub.4].sup.2+ was formed;
[0186] (c) 3.1 ml of 10 mM Cu(CH.sub.3COO).sub.2 solution plus 1 ml
of 1 mM G4.T (metal/dendrimer ratio=31/1
[Cu(CH.sub.3COO).sub.2-G4.T];
[0187] (d) 4.7 ml of 10 mM Cu(CH.sub.3COO).sub.2 solution plus 1 ml
of 1 mM G4.0 (metal/dendrimer ratio =47/1) {Cu.sub.2S-G4.0}.
[0188] Upon introduction of hydrogen sulfide into the reaction
mixtures, the solutions changed from colorless to brown indicating
the formation of CuS. Aqueous Cu.sup.2+ solutions without
dendrimers resulted in an insoluble black CuS which precipitated
quickly. After 16 hour reaction time, the reaction mixtures turned
to dark green indicating a redox reaction with the excess of
hydrogen sulfide. {Cu.sub.2S-G4.T} and {Cu.sub.2S-G4.0} solutions
were deep green but remained transparent. The samples were stored
at room temperature and they proved to be stable for weeks.
Example IIb
Formation of Soluble CdS By Nanoencapsulation:
[0189] Procedure A was used in conjunction with 3.1 ml of 10 mM
(3.1.times.10.sup.-5 mole) aqueous Cd(CH.sub.3COO).sub.2 solution.
The pH of the solution was adjusted with glacial acetic acid
between pH=3 and pH=6 to prevent hydroxide formation. A two-hour
"rest period" was provided.
[0190] Four Aqueous Solutions Were Prepared
[0191] (a) 5 ml 10 mM Cd(CH.sub.3COO).sub.2 solution,
[0192] (b) 5 ml 10 mM Cd(CH.sub.3COO).sub.2 solution plus 2 ml cc.
ammonium hydroxide (NH3 coordination)
[Cd(NH.sub.3).sub.2].sup.2+;
[0193] (c) 3.1 ml of 10 mM Cd(CH.sub.3COO).sub.2 solution plus 1 ml
of 1 mM G4.T (metal/dendrimer ratio =31/1
[Cd(CH.sub.3COO).sub.2-G4.T];
[0194] (d) 4.7 ml of 10 mM Cd(CH.sub.3COO).sub.2 solution plus 1 ml
of 1 mM G4.0 (metal/dendrimer ratio =47/1)
[Cd(CH.sub.3COO).sub.2-G4.0].
[0195] Upon introduction of hydrogen sulfide into the reaction
mixtures, the solutions changed from colorless to yellow indicating
the formation of CdS. Aqueous Cd2+ solutions without dendrimers
resulted in an insoluble yellow CdS which precipitated quickly.
{CdS-G4.T} and {CdS-G4.0} solutions were bright yellow but remained
transparent (FIG. 8). The samples were stored at room temperature
and they proved to be stable for weeks. Evaporation of a drop of
this solution on a glass-slide resulted in a yellow, transparent
and homogenous film, which can be redissolved either in water or in
methanol.
Example IIc
Formation of Soluble PbS by Nanoencansulation:
[0196] Procedure A was used in conjunction with 3.1 ml of 10 mM
(3.1.times.10.sup.-5 mole) aqueous Pb(CH.sub.3COO).sub.2 solution.
The pH of the solution was adjusted with glacial acetic acid
between pH=3 and pH=6 to prevent hydroxide formation. A two-hour
"rest period" was provided.
[0197] Four Aqueous Solutions Were Prepared:
[0198] (a) 5 ml 10 mM Pb(CH.sub.3COO).sub.2 solution,
[0199] (b) 5 ml 10 mM Pb(CH.sub.3COO).sub.2 solution plus 2 ml cc.
arnmonium hydroxide (NH.sub.3 coordination)
[Pb(NH.sub.3)].sup.2+;
[0200] (c) 3.1 ml of 10 mM Pb(CH.sub.3COO).sub.2 solution plus 1 ml
of 1 mM G4.T (metal/dendrimer ratio=31/1
[Pb(CH.sub.3COO).sub.2-G4.T];
[0201] (d) 4.7 ml of 10 mM Pb(CH.sub.3COO).sub.2 solution plus 1 ml
of 1 mM G4.0 (metal/dendrimer ratio=47/1)
[Pb(CH.sub.3COO).sub.2-G4.0].
[0202] Upon introduction of hydrogen sulfide into the reaction
mixture, the color of the solutions changed from colorless to
brownish-black indicating the formation of PbS. Aqueous
Pb.sup.2+solutions without dendrimers resulted in insoluble black
PbS which precipitated quickly. {PbS-G4.T} and {PbS-G4.0} solutions
were brownish-black but remained transparent. The samples were
stored at room temperature and they proved to be stable for several
days.
Example IId
Formation of Soluble ZnS by Nanoencapsulation:
[0203] Procedure A was used in conjunction with 3.1 ml of 10 mM
(3.1 x 10-5 mole) aqueous Zn(CH.sub.3COO).sub.2 solution. The pH of
the solution was adjusted with glacial acetic acid to pH -6 to
prevent hydroxide formation. A two-hour "rest period" was
provided.
[0204] Four Aqueous Solutions Were Prepared
[0205] (a) 5 ml Zn(CH.sub.3COO).sub.2 solution,
[0206] (b) 5 ml Zn(CH.sub.3COO).sub.2 solution plus 2 ml cc.
ammonium hydroxide (NH.sub.3 coordination)
[Zn(NH.sub.3).sub.2];
[0207] (c) 3.1 ml of 10 mM Zn(CH.sub.3COO).sub.2 solution plus 1 ml
of 1 mM G4.T (metal/dendrimer ratio =31/1
[Zn(CH.sub.3COO).sub.2-G4.T];
[0208] (d) 4.7 ml of 10 mM Zn(CH.sub.3COO).sub.2 solution plus 1 ml
of 1 mM G4.0 (metal/dendrimer ratio=47/1)
[Zn(CH.sub.3COO).sub.2-G4.0].
[0209] In the next step, an excess of hydrogen sulfide gas was
introduced into the reaction mixtures. White precipitate was
observed in the Zn(CH.sub.3COO).sub.2 and
[Zn(NH.sub.3).sub.2].sup.2+, solutions indicating the quick
formation of ZnS. {Zn(CH.sub.3COO).sub.2-G4.T} and
{Zn(CH.sub.3COO).sub.2-G4.0} turned to white and hazy but remained
transparent. After 30 seconds bubbling, the tubes were capped and
sealed with parafilm for storage overnight. The samples were
sonicated for 30 min. and purged with nitrogen to remove the excess
of H.sub.2S. The samples were stored at room temperature and they
proved to be stable. Evaporation of the solution on a glass-slide
resulted in a colorless, transparent and homogenous film, which
could be redissolved in methanol and DMSO.
Example IIe
Formation of Soluble CoS by Nanoencapsulation:
[0210] Procedure A was used in conjunction with 3.1 ml of 10 mM
(3.1.times.10.sup.-5 mole) aqueous Co(CH.sub.3COO).sub.2 solution.
The pH of the solution was adjusted with glacial acetic acid to
pH=6 to prevent hydroxide formation. A two-hour "rest period" was
provided to reach the equilibrium state for the metal ion
complexation.
[0211] Four Solutions Were Prepared:
[0212] (a) 5 ml Co(CH.sub.3COO).sub.2 solution,
[0213] (b) 5 ml Co(CH.sub.3COO).sub.2 solution plus 2 ml cc.
ammonium hydroxide (NH.sub.3 coordination)
[Co(CH.sub.3COO).sub.2-NH.sub.3];
[0214] (c) 3.1 ml of 10 mM Co(CH.sub.3COO).sub.2 solution plus 1 ml
of 1 mM G4-T (metal/dendrimer ratio=31/1
[Co(CH.sub.3COO).sub.2-G4.T];
[0215] (d) 4.7 ml of 10 mM Co(CH.sub.3COO).sub.2 solution plus 1 ml
of 1 mM G4.0 (metal/dendrimer ratio=47/1)
[Co(CH.sub.3COO).sub.2-G4.0].
[0216] In the next step, an excess of hydrogen sulfide gas was
introduced into the reaction mixtures. The color of the solutions
changed from colorless to black indicating the formation of
CoS.
[0217] Co.sup.2+ solutions without dendrimers resulted in a small
amount but heavy black CoS which precipitated quickly.
[CoS-NH.sub.3] gave a black precipitate and a light brown liquid
phase, due to (NH.sub.4).sub.2S formation. {CoS-G4.T} and
{CoS-G4.0} solutions were dark black but remained transparent. The
samples were stored at room temperature and they proved to be
stable for more than five days (FIG. 9).
Example IIf
Formation of Soluble FeS by Nanoencapsulation:
[0218] Measured amount of aqueous FeSO.sub.4 solution was mixed
with a calculated amount of aqueous dendrimer solution in a 60 ml
screw-cap test tube. The pH of the resulting solution was adjusted
with glacial acetic acid between pH=3 and pH=6 to prevent hydroxide
formation before diffusion. Dry nitrogen gas was bubbled through
the liquid to remove the air and avoid the formation of sulfur by
oxidation during consecutive steps. A two-hour "rest period" was
provided to reach the equilibrium state for the metal ion
complexation.
[0219] Four Solutions Were Prepared During The First Attempt:
[0220] (a) 5 ml of FeSO.sub.4 solution;
[0221] (b) 5 ml of FeSO.sub.4 solution plus 2 ml cc. ammonium
hydroxide (NH.sub.3 coordination) [FeSO.sub.4-NH.sub.3];
[0222] (c) 3.1 ml of 10 mM FeSO.sub.4 solution plus 1 ml of 1 mM
G4.T (metal/dendrimer ratio=31/1 [FeSO.sub.4-G4.T];
[0223] (d) 4.7 ml of 10 mM FeSO.sub.4 solution plus 1 ml of 1 mM
G4.0 (metal/dendrimer ratio=47/1) [FeSO.sub.4-G4.0].
[0224] In the next step, an excess of hydrogen sulfide gas was
introduced into the reaction mixtures. The color of the solutions
changed from very light green to black indicating the formation of
FeS. Only a small amount of black solid precipitated from the
FeSO.sub.4 solution, but {FeS-G4.T} and {FeS-G4.0} were dark black.
After 30 seconds bubbling, the tubes were capped and sealed with
parafilm for overnight. The samples were sonicated for 30 min. and
purged with nitrogen to remove the excess of H.sub.2S. Fe.sup.2 +
solutions without dendrimers resulted in a small amount of heavy
black FeS, which precipitated quickly. [FeSO.sub.4-NH.sub.3] gave a
plenty of black precipitate due to (NH.sub.4).sub.2S formation.
{FeSO.sub.4-G4.T} and {FeSO.sub.4-G4.0} solutions were dark black
and separated within several hours, indicating that encapsulation
did not occur and the reaction took place outside of the dendrimer.
In the next step, similar samples were prepared, but with G5.T
PAMAM. This experiment again led to the same unsuccessful
capsulation as in the case of G4.T. However, when the "rest time"
was lengthened to 12 hr., the diffusion into the interior did
occur, and H.sub.2S addition resulted in nanocomposite formation.
This transparent black solution was stored at room temperature and
it proved to be stable.
Example IIg
Preparation of {Ag2S-G4.T} Nanocomposite:
[0225] {Ag.sub.2S-G4.T} nanocomposite was made by the method
described in Example Cu#5, except that 0.159 g
(6.19.times.10.sup.-4 mole) silver trifluoromethanesufonate was
used.
[0226] Evaporation of the solvent on a rotavap at 40.degree. C.
yielded a dark brown rigid layer {Ag.sub.2S-G4.T} on the wall of
the flask. This material readily dissolves in water with a dark
brown color. The product was scraped from the wall and the black
solid was transferred into a glass vial. Further drying of the
product under vacuo at room temperature yielded 0.53 g (101%)
nanocomposite as a black solid. Ag content was found to be 14.28%
(theoretical: 12.8%) by atomic absorption (AA) analysis.
Example IIh
Preparation of {Cu.sub.2S-PEI/PEOX G =1.0 Dendrigraft}
Nanocomposite
[0227] Procedure A was applied, except that 10 mM aqueous solution
of PEI/PEOX generation=1.0 dendrigraft (PEI=100, PEOX=100) was used
as host in the same calculated (ligand/metal=4/1) ratio.
[0228] The experimental observation was that a deep blue copper
complex formed in the first step. Upon subsequent H.sub.2S
addition, the solution turns to deep brown, then changes its color
to deep green indicating the formation of {CuS-PEI/PEOX} followed
by the formation of {Cu.sub.2S-PEI/PEOX} nanocomposite. (The {CuS}
nanocomposite can be reduced into Cu.sub.2S by the excess of
reductive H.sub.2S gas). This solution is stable for 24 hrs.
Example IIi
An attempt To Prepare {Cu.sub.2S-PEI/PEOX G=1.0 Dendrigraft}
Nanocomposite
[0229] Procedure A was applied, except that 10 mM aqueous solution
of PEI/PEOX generation=1.0 dendrigraft (PEI=20, PEOX=20) was used
as host in the same calculated (ligand/metal=4/1) ratio.
[0230] The experimental observation was that a deep blue
nitrogen-copper complex formed in the first step. Upon subsequent
H.sub.2S addition, the solution turns to deep brown then deep
green, indicating the formation of {CuS-PEI/PEOX} followed by the
formation of {Cu.sub.2S-PEI/PEOX} nanocomposite. The solution of
{Cu.sub.2S-PEI/PEOX} is unstable, decomposes and within 2 hrs. a
macroscopic precipitate appears.
Example IIj
An Attempt To Prepare {Cu.sub.2S-PEI} Nanocomnosite
[0231] Procedure A was applied, except that 10 mM aqueous solution
of linear polyethyleneimine (PEI, n=100) was used as host in the
same calculated (polymer ligand/metal=4/1) ratio.
[0232] The experimental observation was that a deep blue
nitrogen-copper complex formed in the first step, then the solution
turned to hazy brown after subsequent H.sub.2S addition, indicating
the precipitation of untrapped CuS. (The uncomplexed CuS cannot be
transformed into Cu.sub.2S in solid state).
Example Group III
Preparation of AgOH, AgBr, AgCI, Silver and Gold
Nanocomposites.
Example IIIa
Preparation Of Water Soluble Nanocomposites Containing Silver
Halides and Silver Hydroxide.
[0233] Description Of General Procedure:
[0234] 10 mM solution of CF.sub.3SO.sub.3Ag and 0.1 equivalent
solution of NaCl, KBr and NaOH was prepared by appropriate
dilution. 1 mM aqueous solutions of G4.T and G4.0 was used for
nanoreactors.
[0235] Three Solutions Were Prepared:
[0236] (a) The metal ion solution (Ag.sup.+);
[0237] (b) 3.1 ml of 10 mM Ag.sup.+ solution plus 1 ml of 1 mM G4.T
(Ag+/dendrimer ratio=31/1) [Ag+-G4.T];
[0238] (c) 4.7 ml of 10 mM Ag.sup.+ solution plus 1 ml of 1 mM G4.0
(Ag.sup.+/dendrimer ratio=47/1) [Ag+-G4.0].
[0239] A measured amount of aqueous CF.sub.3SO.sub.3Ag solution was
mixed with a calculated amount of aqueous dendrimer solution in a
15 ml screw-cap test tube. A "rest period" was provided to reach
the equilibrium state for the Ag.sup.+ ion complexation.
[0240] In the next step, 0.5 ml of selected anion solution were
added to the tube to react with the silver ions. Color change
occurred indicating the formation of AgOH, AgCl and/or AgBr. The
tube was capped, sealed with parafilm and stored in the dark. As a
general experience, CF.sub.3SO.sub.3Ag solution when reacted
without dendrimers form instantaneously an insoluble precipitate
that settles quickly. In contrast, in the presence of dendrimers
the reaction yields transparent or slightly hazy solution (as in
the case of AgCl and AgBr) suggesting subcolloidal particle
formation. {Ag(0)-G4.T} and {Ag(0)-G4.0} were also filtered through
a 0.45 microns Teflon filter to remove any macroscopic size
precipitate originated from the complexation of metal ions on the
dendrimer surface. (FIG. 10).
[0241] The samples were stored at room temperature in the dark.
Solutions were found to be stable for hours before macroscopic
precipitation began. Excess of ammonium hydroxide (which forms
complex with any silver salt) caused instantaneous dissolution of
the precipitate in the absence of the dendrimer. However, in the
presence of encapsulated silver compounds the loss of
color/haziness took several seconds. This observation can be
explained by the hindered diffusion through the surface of the
dendrimer that slows down the complexation process.
Example IIIb
Preparation Of {Ag(0)} Nanocomposite:
[0242] 10 mM solution of CF.sub.3SO.sub.3Ag solution in water and
methanol, and 0.1 M aqueous solution of L-ascorbic acid (AA) was
prepared by appropriate dilution. As for dendritic polymers, 1 mM
aqueous solutions of PAMAM G4.T, G5.P and G4.5 was used either in
water or methanol.
[0243] Three Solutions Were Prepared:
[0244] (a) The metal ion solution (Ag.sup.+);
[0245] (b) 3.1 ml of 10 mM Ag.sup.+ solution plus 1 ml of 1 mM
dendrimer solution (Ag.sup.+/dendrimer ratio=31/1) [M-G4.T];
[0246] (c) 3 ml of 10 mM Ag.sup.+ solution plus 1 ml of 10 mM
ethylenediaminetetraacetic acid disodium salt
[Ag.sup.+-EDTA-Na.sub.2].
[0247] A measured amount of CF.sub.3SO.sub.3Ag solution was mixed
with a calculated amount of aqueous dendrimer solution in a 15 ml
screw-cap test tube. A 30 min. "rest period" was provided to reach
the equilibrium state for the Ag.sup.+ ion complexation.
[0248] In the next step, 0.5 ml of ascorbic acid (AA) solution was
added to the tubes to react with the silver ions. In the cases of
(a) and (c), brown precipitation was observed. This color indicated
the formation of Ag(O) metal, which quickly settled.
[0249] When dendrimers were present, yellowish-brown, hazy but
transparent solution formed that was stable for more than 24
hrs.
Example IIIc
Preparation of {Au(O)} Nanocomoosite
[0250] Aqueous solutions of HAuCl.sub.4 (11.8 mM) and 0.1 M of
L-ascorbic acid (AA) was prepared. As for dendritic polymers, 1 mM
aqueous solutions of PAMAM G2.T, G4.T and G7.T were tried.
[0251] Three Solutions Were Prepared In A 15 ml Screw-Cap Test
Tube
[0252] (a) The metal ion solution (HAuCl.sub.4);
[0253] (b) 2 ml of 11.8 mM HAuCl.sub.4 solution plus 1 ml of 1 mM
dendrimer solution (Au.sup.+/dendrimer ratio=23.6/1);
[0254] (c) 2 ml of 11.8 mM HAuCl.sub.4 solution plus 1 ml of 1 mM
ethylenediamine-tetraacetic acid disodium salt.
[0255] A "rest period" was provided to reach the equilibrium state
for the internal salt formation between nitrogens and the
chloroaurate anion.
[0256] In the next step, 0.5 ml of ascorbic acid (AA) solution was
added to the vials to reduce the aurate ions onto metallic gold. In
the cases of (a) and (c) blue/black discoloration was observed.
This color change indicated the formation of Ag(O) metal, which
quickly settled in the form of a brownish solid.
[0257] When dendrimers were present, violet-blue and transparent
solution formed that was stable for more than 24 hrs.
Example Group IV
Preparation Of Methanolic Silver Bromide Solution.
[0258] 0.10 M solution of CF.sub.3SO.sub.3Ag and saturated KBr
(approx. 0.1 equivalent) were prepared in methanol by appropriate
dilution. 27.63% methanolic solution of G=4.0 PAMAM was used for
complexation.
[0259] A measured amount of CF.sub.3SO.sub.3Ag solution was mixed
with a calculated amount of dendrimer solution in a 15 ml screw-cap
test tube. A "rest period" of 30 minutes was provided to reach the
equilibrium state for Ag.sup.+ ion complexation. Two solutions were
prepared:
[0260] (a) The metal ion solution (Ag.sup.+);
[0261] (b) 2.5 ml of 0.10 M Ag.sup.+ solution plus 0.080 ml of
27.63% G4.0 (Ag.sup.+/dendrimer ratio 25/1).
[0262] In the next step, 2 ml of methanolic KBr solution (100%
excess to the Ag.sup.+) was added by means of a pipette into the
vial. Color change indicated the formation of AgBr. The tube was
capped, sealed with parafilm and stored in the dark.
[0263] As a general experience, in the absence of a dendrimer,
instantaneously an insoluble yellowish-white solid precipitated
from the CF.sub.3SO.sub.3Ag solution. This solid became black soon,
as a result of photolysis of AgBr into Ag. In the presence of a
dendrimer a transparent, hazy, white solution formed suggesting
stable, subcolloidal particle formation.
[0264] The {AgBr-G4.0} samples needed no filtration and existed for
a prolonged time in the dark at room temperature. However, under
sunlight the solution developed a light brown color. UV-visible
spectra shows the appearance of a second peak at 405 nm in addition
to the original 300 nm peak (FIG. 11 and FIG. 12).
[0265] Deliberately added excess of ammonium hydroxide (which forms
complex with any silver salt) led to instantaneous dissolution of
the precipitate in the absence of the dendrimer. However, in the
case of nanoencapsulated silver compounds the loss of color took
several seconds because diffusion through the surface of the
dendrimer slows down the reaction.
Example Group V
Preparation Of Metal Sulfide Solutions In Toluene.
[0266] In a 20 ml screw-cap test tube, 5 ml of 10 mM aqueous
Cu.sup.2+-acetate solution was mixed with a 5 ml of 1.43 mM G=4.0
epoxydecane modified (ammonia core) PAMAM dendrimer solution in
toluene. This dendrimer has a hydrophobic surface and is able to
perform complexation only in its interior. The resulting
heterophase solution was shaken for several minutes. Dark blue
color of the organic phase was observed due to the complexation of
copper ions within the dendrimer, which confirms transfer of the
copper ions into the organic layer.
[0267] The dark blue toluene layer was separated and, in the next
step, an excess of hydrogen sulfide gas was introduced into the
reaction mixture to react with the copper ions. The dark blue color
turned into brownish-yellow because of the formation of {CuS}. This
organic reaction mixture remained stable and transparent without
any precipitate for several weeks in a closed vial. (FIG. 13).
[0268] Using aqueous solutions of Ag.sup.+, Cd.sup.2 +, Fe.sup.2+,
Ni.sup.2- and Mn.sup.2+ ions in the same experiment also led to
sulfides solubilized in toluene.
Example Group VI
Comparison Of Sulfide Nanocomposite Formation In Astramol and
Perstorp Dendritic Hosts.
[0269] In this group of examples different guests were reacted
within ASTRAMOL G=4 (DAB(PA).sub.64) and PERSTORP dendritic
polyester (generation five) hosts using Procedure A. Observations
after 48 hours of reaction time are summarized listed (on the next
page) in Table VI.
5TABLE VI Comparison Of ASTRAMOL and PERSTORP Hosts. ASTRAMOL
Dendrimer PERSTORP Dendritic Polyester Metal Reaction Reaction Ion
Solution Precipitate Product Solution Precipitate Product Cu.sup.2+
Dark brown solution that turns No {Cu.sub.2S} Dark brown solution
that stays Some {CuS} to green brown and Cu.sub.2S Fe.sup.3+ Dark
green Some Black {FeS} Colorless Some yellow sulphur Strong and FeS
complexation Hg.sup.2+ Dark brown which turns into No {HgS.sub.br}
Clear, colorless (separated) Black HgS orange to {HgS.sub.r}
Bi.sup.3+ Dark brown No {Bi.sub.2S.sub.3 Dark brown Some dark brown
{Bi.sub.2S.sub.3} and Bi.sub.2S.sub.3 Zn.sup.2+ Yellowish,
homogenous No {ZnS} Clear, colorless (separated) White ZnS
Cd.sup.2+ Bright yellow No {CdS} Bright yellow No {CdS} Co.sup.2+
Black Some {CoS} Clear, colorless (separated) Black CoS and CoS
Pb.sup.2+ Dark brown No {PbS} Clear, colorless (separated) Black
PbS Ag.sup.+ Brown No {Ag.sub.2S} Clear, colorless (separated) Dark
brown Ag.sub.2S Ni.sup.2+ Black Some {NiS} Black Some {NiS} and and
NiS NiS Mn.sup.2+ Yellowish, clear No {MnS} Clear, colorless
(separated) White, flaky MnS Notation: {MeS} denotes a metal
sulfide encapsulated in a nanocomposite. MeS indicates a
macroscopic precipitation of the metal sulfide.
Example Group VII
Preparation Of Magnetic Dendritic Nanocomposites Using Aqueous
Solutions Of Zero Valence Metals.
[0270] In the following examples, dilute aqueous solutions of
FeCl.sub.3 and CoCl.sub.2 were allowed to diffuse into different
hosts and were reduced to zero valence metals within the
dendrimers. In the absence of dendritic polymers, usually a black
colloidal solution formed, which quickly precipitated as a black
solid. However, in the presence of dendrimers, the same procedure
resulted in black or dark brown, but transparent solutions. These
solutions contained nanoencapsulated zero valence metals and
displayed magnetic properties. A sample of these nanocomposite
solutions were placed close to a permanent magnet and the effect of
the magnetic field was observed. The magnet quickly collected the
nanocomposite, and the homogenous black metal solution become
heterogenous and displayed concentration gradient according to the
magnetic field. In the absence of a magnetic treatment, the
nanoencapsulated solution stayed stable and homogenous for a
day.
Example VIIa
[0271] [FeCl.sub.3-G6.T] inorganic-dendrimer internal complex was
prepared by mixing 0.5 ml of 0.5 mM aqueous solution
(0.25.times.10.sup.-6 mole) of G6.T PAMAM and 2.5 ml of 10 mM
aqueous FeCI.sub.3 solution (2.5.times.10.sup.-5 mole). In the next
step, the pH was adjusted with 1-2 drops glacial acetic acid to
prevent the precipitation of the Fe(OH).sub.3. (In the resulting
deep yellow solution the concentrations are:
[Fe]=8.33.times.10.sup.-5 M and [G6.T]=8.33.times.10.sup.-5 M). The
vial was closed and the reaction mixture was allowed to stand for
12 hours at room temperature to give time for the diffusion of the
Fe.sup.3+ ions into the interior of the dendrimer. To this solution
solid sodium borohydride was added in small portions while the vial
was shaken. The solution foams due to the partial decomposition of
the NaBH.sub.4 and changes its color to black/dark grey. Finally,
the solution displays the characteristic metallic grey color of the
elemental iron. Although these metallic iron particles are very
reactive due to their nanoscopic size, the solution is stable for a
day under nitrogen, if magnetic field is not present. After a day,
the metal dissolved again.
[0272] When the sample was placed into a magnetic field, the iron
nanoparticles acquired permanent magnetization, and the
nanocomposite travelled to the magnet followed by a subsequent
formation of a black heterophase. Then, the vial was removed from
the magnetic field and it was vigorously shaken for several
seconds. As the consequence of the applied mechanical stress, the
dark grey solution formed again. However, the residual magnetism of
the iron nanoparticles reduced the lifetime of virtual homogeneity,
and these samples gave rise to crystallite-like agglomerates
similar to iron-filing.
Example VIIb
[0273] Same procedure was used as in Example VIIa, except that
CoCl.sub.2 was used.
[0274] The experimental result is the same, but solution of
{Co(O)-G6.T} is more stable than that of iron, and the
nanocomposite exhibits lesser extent of residual magnetism. Using a
lower generation dendrimer, such as PAMAM G5.OH, the internal
complex forms much faster (in fifteen minutes).
Example VIIc
[0275] Same procedure was used as in Example VIIa, except that
Ni(II)-acetate solution was used.
[0276] The experimental result is similar to Example VIIb, but
{Ni(O)-G6.T} displays a low level of magnetism.
Example Group VIII
Miscellaneous Examples.
[0277] In the following examples, dilute aqueous solutions of
Ca.sup.2+, Gd.sup.2+, Al.sup.3+, UO.sub.2.sup.2+ and Co.sup.2+ were
allowed to diffuse into PAMAM hosts and subsequently were
chemically transformed into different compounds within the
dendrimers. In the absence of dendritic polymers usually a
macroscopic precipitate formed, which quickly precipitated.
However, in the presence of dendrimers, the same procedure resulted
in transparent nanocomposite solutions.
VIII/1
Solubilization of Ca.sup.2+-oxalate In The Form Of Nanocomnosites
Using Dendritic Polymers:
[0278] 0.1 M aqueous solution of CaCl.sub.2, oxalic acid and
EDTA-Na2 was prepared and used in this test. As for dendritic
polymers, 1 mM aqueous solutions of PAMAM G4.T, ASTRAMOL G=4 and
PERSTORP G=5 was used either in water or methanol. For
comparison.
[0279] Five Solutions Were Prepared:
[0280] (a) 1 ml of metal ion solution (Ca.sup.2+);
[0281] (b) To 1 ml of 1 mM dendritic polymer solution 0.3 ml of 0.1
M Ca.sup.2+ solution was added (Ca.sup.2+/dendrimer
ratio=30/1);
[0282] (c) To 1.0 ml 0.1 M aqueous solution of CaCl.sub.2 solution
was added 1.0 ml of 0.1 M ethylenediaminetetraacetic acid disodium
salt (EDTA-Na.sub.2);
[0283] (d) To 1 ml of 1 mM dendritic polymer solution 0.3 ml of 0.1
M oxalic acid solution was added (oxalic acid/dendrimer
ratio=30/1).
[0284] A measured amount of second reactant solution was mixed in a
15 ml screw-cap test tube with the solutions listed above after a
30 min. "rest period". This time was provided to reach the
equilibrium state for the first reactant.
[0285] In the next step, equivalent amount of second reactant was
added to the vials to react with the Reactant#1. (Oxalic acid
solution was used in (a), (b), (c), and Ca.sup.2+ solution was used
in (d)).
[0286] In the case of (a), white crystals precipitated less than a
minute. In the case of (c), white crystals precipitated within
several minutes. Mechanical stress (shaking) did not restore the
suspension.
[0287] When dendritic polymers were present, white, hazy but
transparent solution formed that was stable for more than 5 hrs.
Order of composite precipitation was:
PAMAM<ASTRAMOL<PERSTORP. Vigorous shaking restored the
milk-like appearance.
Example VIII/2
Preparation of Gd.sup.2+-oxalate Nanocomposite Using A Dendritic
Polymer.
[0288] [Gd(CH.sub.3COO).sub.2-G4.T] internal complex was prepared
by mixing 1.0 ml of 1.0 mM aqueous solution (1.times.10.sup.-5
mole) of G4.T PAMAM and 3.1 ml of 10 mM aqueous
Gd(CH.sub.3COO).sub.2 solution (3.1.times.10.sup.-4 mole). The vial
was closed and the reaction mixture was allowed to stand for 0.5
hours at room temperature to give time for the diffusion of the
Gd.sup.2+ ions into the interior of the dendrimer. To this solution
2 ml of 10 mM oxalic acid solution was added. When dendritic
polymer was present, the solution remained colorless and
transparent but macroscopic, crystalline, white precipitate was
observed in the absence of the polymer.
Example VIII/3
Preparation Of Al(OH).sub.3 Nanocomposite Using A Dendritic
Polymer.
[0289] [Al.sub.2(SO.sub.4).sub.3-G4.T] internal complex was
prepared by mixing 1.0 ml of 1.0 mM aqueous solution
(1.times.10.sup.-5 mole) of G4.T PAMAM and 1.5 ml of 10 mM aqueous
A1.sub.2(SO.sub.4).sub.3 solution (1.5.times.10.sup.-4 mole). The
vial was closed and the reaction mixture was allowed to stand for
0.5 hours at room temperature to give time for the diffusion of the
Al.sup.3+ ions into the interior of the dendrimer. To this solution
1.0 ml of 10 mM NaOH solution was added. When dendritic polymer was
present, the solution remained colorless and transparent, but
macroscopic, flaky, white (Al(OH).sub.3 precipitate was observed in
the absence of the polymer.
Example VIII/5
Preparation Of Uranyl Phosphate Nanocomposite Using A Dendritic
Polymer.
[0290] [Uranyl phosphate - G4.T] internal complex was prepared by
mixing 1.0 ml of 1.0 mM aqueous solution (1.times.10.sup.-5 mole)
of G4.T PAMAM and 3.0 ml of 10 mM aqueous
UO.sub.2(CH.sub.3COO).sub.2 solution (3.0.times.10.sup.-4 mole).
The vial was closed and the reaction mixture was allowed to stand
for 1 hour at room temperature to give time for the diffusion of
the uranyl ions into the interior of the dendrimer. To this
solution 3.0 ml of 10 mM Na.sub.3PO.sub.4 solution was added. When
dendritic polymer was present, the solution turned to yellow but
remained transparent. In the absence of the polymer, a macroscopic,
flaky, yellow uranyl phosphate precipitate was observed.
Example VIII/6
Preparation Of Cobalt(II) Hydroxide Nanocomposite Using A Dendritic
Polymer
[0291] [CoCl.sub.2-G4.T] internal complex was prepared by mixing
1.0 ml of 1.0 mM aqueous solution (1.times.10.sup.-5 mole) of G4.T
PAMAM and 3.1 ml of 10 mM aqueous CoCl.sub.2 solution
(3.1.times.10.sup.-4 mole). The vial was closed and the reaction
mixture was allowed to stand for 0.5 hours at room temperature to
give time for the diffusion of the Co.sup.2+ions into the interior
of the dendrimer. To this solution 50 microliter of 35% hydrazine
solution was added. When dendritic polymer was present, the
solution turned to yellow but remained transparent. In the absence
of the polymer, a macroscopic, flaky, green cobalt(II) hydroxide
precipitated promptly.
Example IX/1
Formation Of Gold Nanoparticles In The Presence Of Dendrimers
[0292] A) Using PAMAM dendrimer with aliphatic OH surface
groups
[0293] Aqueous solutions of HAuCl.sub.4 (10.4 mM) and 1.0 mM of
PAMAM G4.T were prepared. To 3 ml of distilled water 50 ul of this
G4.T solution was added and then mixed with 50 pl of HAuCl.sub.4.
The solution within minutes develops an intensive red color due to
the formation of colloidal gold nanoparticles. UV-visible spectra
for slightly different preparation methods indicate a peak within
530 and 550 nm (FIG. 14), that suggest a size of .about.50 A for
these particles (M.Moller et al., Chem. Eur. J. 1966, 2(12, 1552).
The development of the color can be accelerated by using 10 .mu.l
of 3% hydrazine solution to reduce the otherwise spontaneously
decomposing Au(OH).sub.3 which precipitated in the interior of the
G4.T dendrimer into elemental gold.
[0294] B) Using a PAMAM dendrimer with amino surface groups
[0295] Aqueous solutions of HAuCl.sub.4 (10.4 mM) and 1.0 mM of
PAMAM G4.0 were prepared.
[0296] To 100 .mu.l of HAuCl.sub.4 stock solution
(5.02.times.10.sup.-7 mole) that was diluted to 2.0 ml was added
250 .mu.l of G5.0 solution (2.17.times.10.sup.-6 m) followed by
0.25 ml of 3% hydrazine solution at room temperature. TEM
micrograph shows that under these conditions the decomposition of
tetrachloroaurate takes place on the surface of the macromolecule.
This procedure results in dendrimer clusters with 50-60 nm diameter
that are made of individual dendrimers covered and connected by
elemental gold (FIG. 16).
[0297] When the order of mixing was changed and the hydrazine
solution was added to the dendrimer solution before the
tetrachloroaurate, a fast reduction occurs, and non-clustered
particles were formed. Their diameter appears to be identical to
the dendrimer molecules (FIG. 17). Treatment of the red gold
colloid solution with elemental bromine results in the formation of
multiclusters, with an average diameter of 100 nm. This is an
excellent example how to control the size of the gold particles by
changing the addition order of chemicals or the chemicals
themselves. (FIG. 18).
Example IX/2
Generation Dependence Of CuS and Cu.sub.2S Nanocomposite Formation
(Illustration of scaffolding properties of generations with high
surface densities)
[0298] In this series of TEM experiments, EDA-core PAMAM dendrimers
with amino surface (Gn.0) were utilized to demonstrate the
pattern-change in making CuS and Cu.sub.2S nanocomposites when
different generations are used. The gradual decrease of the
distance between surface groups is the reason for this change, and,
as a consequence, the decrease in penetrability. As the size of the
copper-hexaaqua-complex is constant, below G=7 copper is able to
enter the interior of the dendrimer, and precipitates within the
interior when sulfide ions are added. This pattern leads to black
dots or shapes (clusters, etc.) formed from dark spots on the
unstained TEM micrograph, because of the high electron adsorption
of the metal.
[0299] This pattern changes to regular arrays of white spots in an
arrangement similar to hexagonal closed packing surrounded with
dark areas when PAMAMs of G=7 or higher are used. The reason is
that in those cases, when the copper-hexaaqua-complex is unable to
penetrate the surface, upon reaction with sulfide ions it turns
into a insoluble sulfide on the surface. The copper sulfide then
interconnects several dendrimer molecules forming berry-like
structures that preferably self assemble into chains.
[0300] As a general procedure, EDA-core PAMAM dendrimers with amino
surface were dissolved in a dilute solution (1-2 mg/ml), and a
calculated amount of copper acetate solution was added.
(Concentration of copper was identical to the concentration of
nitrogen in the dendrimer.) The solution was mixed by bubbling
nitrogen gas through the solution. After a certain time (30 minutes
-2 hr) H.sub.2S gas was introduced into the solution in excess. The
solution was again flushed with N.sub.2 and analyzed by TEM. The
procedure resulted in dark brown solutions of soluble CuS
nanocomposites that changes slowly into dark green ({Cu2S}). (FIGS.
19-21).
Example IX/3
Crosslinking of PAMAMA G4.0 with terephtaldicarboxaldehyde
(TPTDCA):
[0301] Difunctional monomers are especially useful in linking
dendritic polymers. Examples are methacroyl chloride, acroyl
chloride, methacroyl anhydride, acroyl anhydride, diepoxides,
glycidylmethacrylate, 1,6-diisocyanato-hexane, ethyleneglycol
dimethacrylate, 1,8-diepoxyoctane, ethyleneglycoldiglycidyl-ether,
epichlorohydrin, terephtaldicarboxaldehyde, etc. 1.715 g TPTDCA
(128.times.10.sup.-4 m) was dissolved in 65 ml of methanol at room
temperature. To this solution 7.79 g MeOH solution of PAMAM G4.0
(1.421 g, 1.0.times.10.sup.-4 m) was added dropwise at room
temperature. In 15 minutes, a white, milky solution formed. This
solution was transferred into a refrigerator and was kept at
-5.degree. C. It is stable at this temperature. During dialysis, or
when it is exposed to air, a white gel forms. (In the first step, a
soluble Schiff-base is formed). This gel slowly loses methanol, and
can be dried into a tough, rubbery material, a crosslinked
dendrimer. This crosslinking may be carried out both in the absence
and in the presence of metal ions.
Transformation of a TPTDCA crosslinked G4.0 dendrimer into a
copper-sulfide nanocomposite
[0302] Crosslinked solid gel particles were placed into a 10 mM
Cu(II)-acetate solution overnight. The yellowish dry gel turned
into dark green, indicating the binding of copper ions to the
nitrogen ligands in the dendritic domains of the gel. Exposure of
this Cu.sup.2+into CuS. Because Cu.sup.2+ do not diffuse in solid
phase and copper ions bind only to the ligands, distribution of the
incorporated CuS must be identical to the distribution of the
dendrimers in the solid material. Thus, the distribution of CuS is
created, determined and controlled by the G4.0 PAMAM dendrimer.
Example IX/4
Crosslinking of a metal ion containing dendrimer into a
metal-dendrimer nanocomposite
[0303] To a 1 ml methanolic solution of an EDA-core G5.0 PAMAM
(25.05%, 250 mg, 8.67 hex 06 mole) was added 0.86 ml of 0.1 M
methanolic CoCl.sub.2 solution (20.64 mg, 8.67.times.10.sup.-5
mole). After five minutes, 74.4 mg (1.162.times.10.sup.-3 mole)
TFTDCA was added in a 10% methanolic solution followed by 100 mg of
NaBH.sub.4. While crosslinking by TFTDCA (formation of Schiff-base)
at room temperature requires 10-15 seconds, addition of a
NaBH.sub.4 not only provides stable
--NH--CH.sub.2-Ph--CH.sub.2-NH-- linkages between dendrimers, but
reduces the coordinated Co salt into a magnetic Co.sub.4B compound.
Final appearance of the product is a black gel, that can be dried
under nitrogen into a black solid.
Example IX/5
Preparation of a metal-dendrimer nanocomposite in a silicate
matrix
[0304] 0.270 g G4.T dendrimer and 0.045 g copper (II) acetate were
dissolved in 2.0 ml of water giving a dark blue solution of the
[(CuAc.sub.2).sub.15-G4.T] internal complex. To this solution, 5 ml
of tetraethylorthosilicate (Aldrich) and 4 ml of ethanol was mixed,
and the mixture was poured into a Petri-dish. After two days, the
solution has separated into a colorless upper phase and a solid,
dark blue lower phase. The upper phase was decanted, and the lower
phase was dried at room temperature resulting in 0.45 g hard, deep
blue solid, a silicate matrix containing the [(CuAc.sub.2).sub.15
-G4.T] internal complex. Further heating of this modified silicate
(0.16 g) at 180.degree. C. for two days, brought about the
decomposition of the PAMAM (decomposition temperature is
110-130.degree. C.) and provided a hard, dark brown Cu-oxide
nanocomposite in the silicate matrix. 0.17 g of the same modified
silicate matrix, SiO.sub.4{[CuAc.sub.2).sub.15-G4.T]}, was treated
with H.sub.2S in a closed vial, and gave 0.18 g
SiO.sub.4{[CUS).sub.15-G4.T]} nanocomposite in the form of a dark
brown solid.
[0305] Note:
[0306] Surface-functionalities are available for further
transformations even when they are in use as ligands. Due to its
higher stability, a covalent bond can form also with those ligands
that are actively binding to a metal or metalloid, see, e.g.
reaction of [(CuAc.sub.2).sub.31-G4.0] with 1,2-epoxyhexane.
Example IV/6
Surface modification of a copper(II) internal complex
[(CuAc.sub.2).sub.31-G4.0]
[0307] To a 1 ml methanolic solution of 56.8 mg EDA-core G4.0 PAMAM
(4.0.times.10.sup.-6 mole) was added 37.5 mg (2.56.times.10.sup.-4
mole) copper(II) acetate. When all the inorganic compound dissolved
1 ml of 1,2-epoxyhexane was added (equivalent amount: 30.85 .mu.l)
and it was reacted for 64 hours. The color of the solution turned
to greyish-blue. Removal of solvent on a rotavap gave 0.141 g blue
solid in the form of a film, that was insoluble in
methylenechloride, chloroform, toluene, and water, but it is
soluble in methanol. This intermediate product is a spherical
dendrimer surrounded with n-alkene chains
[(CuAc.sub.2).sub.31-G4.NHCHCH(OH)C.sub.4H.sub.10], containing
complex copper ions in its interior. 0.070 g of this material was
dissolved in 2.5 ml methanol and 10 ml of 30% hydrazine solution
was added. Addition of the reducing agent instantaneously reduces
the copper and results in a light brown solution that turns to red
in five minutes. The appearance of the dispersion peak on the
UV-spectrum shown in FIG. 15 and its position suggest Cu(O)
particles of 50 A size that corresponds to the size of the inverted
dendritic covalent micelle (PAMAM G4.0 molecule with covalently
attached hexyl chains).
Example IV/7
Synthesis and modification of a PAMAM-methacrylate resin
(G2(OH)-MMA) into a nanocomposite film
[0308] From 13.8 g 36.3% methanolic solution of a EDA-core PAMAM
G=2 with an ethanolamine surface (G2(OH), Mw=4352) the solvent was
evaporated on a rotavap and by storing the resulting viscous solid
material under vacuum for three days. G2(OH) was dissolved in 50 ml
of DMF and transferred into a 500 ml three-neck round-bottom flask
equipped with a dropping funnel, N.sub.2 line and mechanical
stirrer. After cooling to 0.degree. C., 6.0 ml triethylamine (43
mmole) was added and 3.5 ml methylmethacroyl chloride (90% 34.8
mmole) diluted with 5 ml DMF was added dropwise. The mixture was
stirred overnight, then it was diluted with 200 ml water and
extracted with CH.sub.2Cl.sub.2. After the first dilution with
water, a yellow precipitate was floating in between the phases,
which was filtered off before extraction and was found to be a
crosslinked PAMAM. Drying gave 3.49 g yellow polymer, while
extraction with methylenechloride yielded 0.69 g monomeric
acrylated PAMAM dendrimer in the form of a viscous liquid that was
stored in the freezer.
[0309] A fraction of this yellow polymer was immersed into a
saturated methanolic solution of Cu(II) acetate. Within fives
minutes, the resin turned into a very dark blue material indicating
the diffusion and strong complexation of Cu-ions in the PAMAM
matrix. Storing the modified matrix under H.sub.2S gas results in a
black CuS nanocomposite.
Example IX/8
Synthesis and modification of a Perstorp polyester-methacrylate
resin (PS-G4)-MMA) into a CuS containing nanocomposite matrix or
film
[0310] (The applied procedure is a modification of the synthesis
described by M Johannson, A. Hult in the J of Coatings Technology
67, No. 849, Oct. 1995, p. 36.)
[0311] 5.01 g (6.84.times.10.sup.-4 mole) generation four Perstorp
polyester was placed into a 100 ml round bottom flask and melted by
a heat-gun. The resulting melt was dissolved in 25 ml methanol,
then stripped from the solvent and dried. 9.75 ml triethylamine and
the polyester were dissolved in 35 ml THF and cooled to 0.degree.
C. on an ice-bath. 6.0 ml of methylmethacroyl chloride was diluted
with 20 ml of THF and added dropwise while maintaining the
temperature. The temperature was raised overnight and the solvent
was evaporated on a rotavap. The residue was redissolved in 50 ml
methylenechloride and it was washed with water, Na2CO.sub.3
solution and water again. Dried overnight over anhydrous sodium
sulfate. The resulting material contains 65% methacrylate esters on
stoichiometrically substitutable aliphatic OH groups (36-38
MMA/molecule). It is stable when kept in a dilute CH.sub.2Cl.sub.2
solution. Removal of solvent causes immediate polymerization, and
the honey-like liquid gels quickly. It was partially redissolved in
methylenechloride thus separating the still soluble monomeric form
from the already crosslinked material that was filtered and dried
on air.
[0312] The polymer gave 3.56 g light brownish solid. Color of this
solid changes into greyish-blue (Cu-complex in the matrix) when
immersed into a saturated a methanolic solution of Cu(II) acetate.
This Cu-complex containing matrix can be transformed into a dark
brown, CuS containing nanocomposite by treating the modified matrix
with H.sub.2S.
[0313] Solution of the soluble monomeric form in methylenechloride
is perfectly miscible with 0.1 M methanolic solutions of Ni.sup.2+,
Cu.sup.2+, Fe.sup.3+, and Co.sup.2+ ions. From these solutions,
films can be cast on glass slides, containing reactive Ni.sup.2+,
Cu.sup.2+, Fe.sup.3+, and Co.sup.2+ ions that can also be further
reacted into nanocomposites.
Example IX/9
Crosslinking of a G4.0 PAMAM dendrimer with methacroyl chloride and
its modification into a CuS containing nanocomposite
[0314] 5.06 g EDA-core generation four amino surface PAMAM (G4.0,
3.56.times.10.sup.-4 mole) is dissolved in 45 ml anhydrous DMF and
25 ml pyridine. This solution was cooled to 0.degree. C. and 3.0 ml
methylmethacroyl chloride (diluted with 10 ml DMF) was added in
fives minutes. In additional 30 minutes, a transparent,
orange-colored gel formed on the wall of the flask as the main
reaction product. It is not soluble in MeOH but swells and forms a
soft gel. A piece of this polymer was placed into 0.1 molar aqueous
Cu(II) acetate solution. It quickly turns dark blue indicating the
complexation of Cu.sup.2t ions with the PAMAM molecules. Treatment
of the dry blue resin with H.sub.2S quickly changes the color to
dark brown because of the formation of the CuS nanocomposite.
[0315] It will be apparent to those skilled in the art that various
modifications to the preferred embodiment of the invention as
described herein can be made without departing from the spirit or
scope of the invention as defined by the appended claims.
* * * * *