Note: Descriptions are shown in the official language in which they were submitted.
CA 02660069 2009-03-24
METAL COMPLEXES FOR ENHANCED DISPERSION OF NANOMATERIALS,
COMPOSITIONS AND METHODS THEREFOR
FIELD OF THE INVENTION
The present invention relates generally to the compatibilization of
nanomaterials to various matrix materials as well as to related compositions
and
methods therefor.
The present invention relates more specifically to metal
complexes, herein also termed "compatibilizers," that non-covalently
bond/adsorb
onto the surface of nanomaterials, such as carbon nanotubes, to yield a
treated
nanomaterial that can easily be dispersed into a solvent-based matrix material
such
as a protic solvent. From there, the solvated matrix material can be either
further
dispersed, or dried and further dispersed, with or without other materials,
into other
matrix materials, such as, for example, monomers, oligomers and/or polymers,
thereby producing a composite material that has enhanced mechanical, thermal
and
electrical properties.
The composites may have end-use applications in the
aerospace, automotive, biomedical, textile, and electronic fields.
BACKGROUND OF THE INVENTION
Applications for carbon nanotubes are enormous due to their mechanical,
thermal, and electronic properties.
Incorporation and dispersion of carbon
nanotubes into polymers have proven difficult due to the inherent bundling of
the
carbon nanotube due to van der waal forces and incompatability at the
polymer/nanotube (NT) interface.
Pristine nanotubes are generally insoluble/incompatible in common solvents,
oligomers and polymers. Such nanotubes are also difficult to chemically
functionalize without altering the desirable intrinsic properties of
nanotubes. Single-
walled nanotubes (SWNTs) have been solubilized/dispersed in organic solvents
and
water by polymer wrapping (Dalton et al., (J. Phys. Chem. B (2000) 104,
10012);
Star et al. (Angew. Chem., Int. Ed. (2001) 40, 1721), and O'Connell et al.
(Chem.
1
CA 02660069 2016-02-18
Phys. Lett. (2001) 342, 265)), and non-covalently functionalized by adhesion
of small
molecules for protein immobilization (Chen et al., (J. Am. Chem. Soc. 123:3838
(2001))). The polymer wrapping approach works poorly for dissolution of small
diameter SWNTs possibly due to unfavorable polymer conformations.
One known process for non-covalent functionalization and for dispersion of
carbon nanotubes is described by Chen, J. et al. (J. Am. Chem. Soc., 124, 9034
(2002)). The process results in nanotube dispersion using a non-wrapping
approach. Specifically, SWNTs were solubilized in chloroform with
poly(phenylene
ethynylene)s (PPE) along with vigorous shaking and/or short bath-sonication as
described by Chen et al. (ibid) and in U.S. Patent Publication No. U.S.
2004/0034177 published Feb. 19, 2004, and U.S.Patent No. 6,905,667.
The chemistry of arene-silver(I) complexes is well established.
Many
examples exist in the literature to demonstrate the ability of Ag(I) to
coordinate to
polyaromatic systems in a 7c-bonding fashion (see, for example, Megumu et.
al.,
Coordination Chemistry Reviews 2000, 198, 171-203).
Further, the use of certain types of metal complexes, such as certain types of
silver complexes, for compatibilizing nanomaterials, and related compositions,
and
methods therefor, have been described in PCT Publication No. WO 2007/050408,
developed by the inventor of record.
Still other metal complexes have been developed based upon the use of an
organic material being coordinate-bonded to the metal cation, as more fully
described in PCT Publication No. WO 2007/139244.
2
CA 02660069 2009-03-24
The development of metal complexes for compatibilizing nanomaterials,
related compositions, and methods therefore, is on-going, and at least one
more
development is provided herein.
SUMMARY OF THE INVENTION
The present invention provides a metal complex for compatiblizing a
nanomaterial into a matrix, the metal complex comprising a metal cation
capable of
being adsorbed onto a surface of the nanomaterial; and an inorganic surfactant
anion compatible with the matrix. The inorganic surfactant anion employed is
now
capable of stabilizing the metal complex and stabilizing any interactions
between the
metal complex and the nanomaterial, and between the metal complex and the
matrix
such that the metal complex is devoid of any neutral donor ligands attached to
the
metal cation.
The present invention also provides a coating for a surface of a nanomaterial,
the coating comprising a metal complex containing a metal cation capable of
being
adsorbed onto the surface of the nanomaterial; and an inorganic, anionic
surfactant
capable of stabilizing the metal complex and stabilizing any interactions
between the
metal complex and the nanomaterial. The metal complex is devoid of a neutral
donor ligand attached to the metal cation.
The present invention further provides a nanocomposite comprising a matrix;
and a nanomaterial treated with a metal complex and dispersed in the matrix.
The
metal complex contains a metal cation capable of being adsorbed onto a surface
of
the nanomaterial; and a inorganic surfactant anion compatible with the matrix
capable of stabilizing the metal complex and stabilizing any interactions
between the
metal complex and the nanomaterial, and between the metal complex and the
matrix. Moreover, the metal complex is devoid of a neutral donor ligand
attached to
the metal cation.
3
CA 02660069 2009-03-24
Still further, the present invention provides a method for making a
nanocomposite comprising a matrix containing a solvent and a nanomaterial,
wherein the nanomaterial is compatible with the matrix upon treatment thereof.
The
method comprises treating the nanomaterial with a metal complex, the metal
complex containing a metal cation and an inorganic surfactant anion, and
wherein
the metal complex is devoid of a neutral donor ligand, wherein the metal
cation is
adsorbed onto a surface of the nanomaterial, wherein the inorganic surfactant
anion
is compatible with the matrix, and stabilizes the metal complex and stabilize
any
interactions between the metal complex and the nanomaterial, and between the
metal complex and the matrix; and dispersing the treated nanomaterial into the
matrix.
Still another embodiment of the present invention provides a method for
making a nanocomposite comprising a matrix and a nanomaterial, wherein the
nanomaterial is compatible with the matrix upon treatment thereof. The method
comprises treating the nanomaterial with a metal complex, the metal complex
containing a metal cation and an inorganic surfactant anion, and wherein the
metal
complex is devoid of a neutral donor ligand, wherein the metal cation is
adsorbed
onto a surface of the nanomaterial, wherein the inorganic surfactant anion is
compatible with a solvent, and stabilizes the metal complex and stabilize any
interactions between the metal complex and the nanomaterial, and between the
metal complex and the solvent; dispersing the treated nanomaterial into the
solvent;
and dispersing the treated nanomaterial into the matrix.
Yet another embodiment of the present invention provides for an article
comprising a nanocomposite made of a matrix and a nanomaterial, wherein the
nanomaterial is compatible with the matrix upon treatment thereof. The method
comprises treating the nanomaterial with a metal complex, the metal complex
containing a metal cation and an inorganic surfactant anion, wherein the metal
complex is devoid of a neutral donor ligand, wherein the metal cation is
adsorbed
onto a surface of the nanomaterial, wherein the inorganic surfactant anion is
4
CA 02660069 2009-03-24
compatible with a solvent and stabilizes the metal complex and stabilize any
interactions between the metal complex and the nanomaterial, and between the
metal complex and the solvent; dispersing the treated nanomaterial into the
solvent,
and subsequently dispersing the treated nanomaterial into the matrix.
The advantages of the present invention over existing prior art relating to
the
connpatibilization of nanomaterials, such as, for example, carbon nanotubes,
with
matrix materials, such as, for example, solvents, monomers, polymers, and the
like,
which shall become apparent from the description which follows, are
accomplished
by the invention as hereinafter described and claimed.
DESCRIPTION OF ONE OR MORE EMBODIMENTS OF THE INVENTION
As noted hereinabove, at least one embodiment of the present invention
provides for a metal complex having properties that are particularly useful
and
suitable for compatibilizing nanomaterials with a matrix material such that,
upon
subsequent dispersion of the nanomaterials into the matrix material, a useful
nanocomposite is provided that can be used as an useful article or as a
precursor to
improving another article.
In at least one embodiment, the metal complex includes a metal cation
capable of being adsorbed onto a surface of the nanomaterial and an inorganic
surfactant anion compatible with the matrix. Notably, unlike some metal
complexes,
these metal complexes do not include a neutral donor ligand attached to the
metal
cation. The metal complex can be made by any technique known in the art, but
must have at least one functional group capable of compatibilizing the
nanomaterial.
This means that at least one unit of the metal complex is a substituent
capable of
interacting with another chemical group to form a covalent or non-covalent
bond.
Similarly, in another embodiment, the metal complex must also have a
substituent or
functional group capable being compatible with the matrix material. In the
present
invention, the metal cation is preferably the substituent that is capable of
interacting
5
CA 02660069 2009-03-24
with the nanomaterial while the inorganic anionic surfactant is the
substituent that is
capable of interacting with the matrix.
The metal cation can be any metal cation known to be useful for the purposes
of the present invention. That is, essential any non-radioactive metal capable
of
being non-covalently bonded or adsorbed onto the surface of a desired
nanomaterial
can be used. Such metal cations may include any of the alkali metals, alkaline
earth
metals, or the transition metals from groups 4-12 of the transition series of
the
periodic table.
In one embodiment, the metal cation is silver. Silver complexes have
properties that are believed to be particularly useful for compatibilizing
certain types
of nanomaterials, such as carbon nanotubes, and for effecting subsequent
dispersion of a solid nanomaterial within a matrix material such as a solvent
or
polymer. In addition, the use of silver cations can be useful because
silver
complexes are known to have anti-microbial properties associated with them. In
another embodiment, the metal cation is copper.
Essentially any inorganic anionic surfactant compatible with the matrix
material can be used in the present invention. More particularly, it will
be
appreciated that such an inorganic anionic surfactant may include any
inorganic and
anionic species that would balance the charge of the metal cation selected and
be
useful to the present invention. The inorganic anionic surfactant may be a
mono-
anion, an oligomeric anion, or a polyanion.
In at least one embodiment of the present invention, the inorganic surfactant
anion can be any molecular moiety useful as a counteranion and capable of
acting
as a connpatibilizer between the desired nanomaterial and the desired matrix
material. Such anions may include, but are not limited to, a moiety selected
from the
group of nitrate, triflate, sulfate, sulfonate, phosphate and silicate. These
anionic
surfactants work particularly well with silver cations in the formation of
metal
6
CA 02660069 2009-03-24
complexes, such as silver(I) silicates for example, that are believed to be
excellent
compatibilizers of carbon nanomaterials as discussed hereinbelow. One
particularly
useful metal complex is silver silicate, wherein the metal cation is silver
and the
inorganic surfactant anion is a silicate or montmorillonite, such as present
in various
types of inorganic mineral clays.
In one embodiment of the present invention, the inorganic surfactant anion
may optionally have a surfactant tail. Such a tail may be organic or inorganic
in
nature, but the surfactant anion itself will remain inorganic. Such a tail an
be a long
tail having 10 atoms or more in its backbone chain, or a short tail, having
less than
10 atoms in its chain. It will be appreciated that the longer the chain
forming the
surfactant tail, the easier the surfactant tail can debundle the nanomaterial,
such as
nanotubes, that may be held together by van der waal's forces and the like,
and the
easier it can prevent the re-aggregation of the nanomaterial. Of course, such
a
surfactant tail may also aid in the ability of the metal complex to act as a
compatibilizer between the desired nanomaterial and the desired matrix
material.
The surfactant tail may be linear, branched or cyclic. Where suitable, the
surfactant tail of the inorganic anionic surfactant may include from 1 to
about 100
carbon atoms. As such, the surfactant tail may contain an organic functional
moiety
selected from the group consisting of aromatic, alkyl, olefinic, allyl, ether,
amide,
carboxylic, carbonate, and combinations and mixtures thereof. Such organic
tails
may be useful for compatibilizing those nanomaterials and those matrix
materials
that, while not necessarily compatible with each other, are compatible with
the metal
complexes of the present invention having such organic functional moieties.
In another embodiment, the inorganic surfactant anion may employ a
surfactant tail comprising from 1 to about 100 inorganic atoms. As such, the
surfactant tail may contain a functional moiety selected from the group
consisting of
silanes, siloxanes, germanes, germoxanes, stannanes, stannoxanes, phosphanes,
phophenes, arsanes, arsenes, and combinations and mixtures thereof. Of course,
7
CA 02660069 2009-03-24
inorganic tails such as these may also be suitable for compatibilizing those
nanomaterials and those matrix materials that, while not necessarily
compatible with
each other, are compatible with the metal complexes of the present invention
having
such inorganic functional moieties.
In the present invention, it will be appreciated that it is the metal cation
that
attaches to or bonds to the nanomaterial, and the inorganic surfactant anion
that is
compatible with the matrix material into which the nanomaterial treated with
the
metal complex of the present invention will be mixed. In the prior art, it is
often the
anionic species of a metal complex that is bonded to the nanomaterial, thereby
preventing the use of an inorganic anionic surfactant to act as the
compatibilizer
between the nanomaterial and the matrix material into which it is mixed.
Furthermore, it will be appreciated that, in one embodiment of the present
invention, the inorganic surfactant anion comprises a plurality of anionic
compounds,
thereby forming polyanionic compounds. In this embodiment, it is understood
that
one polyanionic strand will interact with several metal cations to yield a
large portion
of the nanomaterial compatible with a large portion of the matrix material.
As noted earlier, the present invention differs from many metal complexes
useful for enhancing dispersion of nanomaterials in a matrix in that the metal
complexes of the present invention are devoid of a neutral donor ligand. A
"neutral
donor ligand" may be defined as a monofunctional or multifunctional (i.e., has
one or
more functional groups) compound attached to the metal cation; hence the use
of
the word "ligand." Prior art metal complexes required neutral donor ligands
that
were capable of stabilizing the metal complex, or capable of stabilizing any
interactions between the metal complex and the nanomaterial or any
interactions
between the metal complex and the matrix material. In the present invention,
the
inorganic surfactant anion is capable of providing these stabilities. Such
prior art
neutral donor ligands include phosphate ester, phosphine, amine and pyridine.
A
multi-functional neutral donor ligand, bipyridine, was explicitly disclosed
and required
8
CA 02660069 2009-03-24
in the owner of record's prior PCT application, PCT Publication No.
W02007/050408.
In view of the foregoing, a metal complex of the present invention may be
depicted schematically as shown in Formula I below:
M-W
(I)
wherein M is a metal cation and W is an inorganic surfactant anion. Again, the
present invention is devoid of any neutral donor ligands.
In one embodiment, the metal complex may be a silver complex. One
example of a silver complex suitable for use in the present invention is shown
in
Formula (II) below.
ig
0
0=s=0
0 ___________________________ \
(II)
Yet another embodiment of the present invention provides a metal complex
for use as a coating for a surface of a nanomaterial. The coating comprises a
metal
complex containing a metal cation capable of being adsorbed onto the surface
of the
9
CA 02660069 2009-03-24
nanomaterial and an inorganic anionic surfactant attached to the metal cation.
The
inorganic anionic surfactant is capable of stabilizing the metal complex and
stabilizing any interactions between the metal complex and the nanomaterial.
The term "nanomaterial," as used herein, includes, but is not limited to,
carbon nanotubes (including multi-wall carbon nanotubes and single-wall carbon
nanotubes), carbon nanoparticles, carbon nanofibers, carbon nanoropes, carbon
nanoribbons, carbon nanofibrils, carbon nanoneedles, carbon nanosheets, carbon
nanorods, carbon nanohoms, carbon nanocones, carbon nanoscrolls, graphite
nanoplatelets, graphite nanoparticles, nanodots, other fullerene materials, or
a
combination thereof. The term, "multi-wall," is meant to include double-wall
nanotubes (DWNTs) and few-wall nanotubes (FWNTs). In one embodiment the
nanomaterials are made from carbon, given that the present invention is
generally
directed to a method of dispersing carbon-based nanomaterials into matrix
materials
with which such nanomaterials typically are not compatible.
The term "nanotubes" may be used broadly herein in some instances and,
unless otherwise qualified or more strictly identified, is intended not to be
limited to
its technical definition. In a technical sense, a "nanotube" is a tubular,
strand-like
structure that has a circumference on the atomic scale. However, it will be
understood that other nanomaterials would work with the present invention.
A method for making metal complexes of the present invention comprises
reacting the metal salt with the inorganic anionic surfactant. For example,
the
reaction of silver nitrate with sodium dodecyl sulfate yields the silver(I)
dodecyl
sulfate complex. In another example, the reaction of silver nitrate with an
inorganic
clay, such as sodium silicate, yields a silver silicate complex. Notably, no
neutral
donor ligands are added to the reaction or to the complex after completion of
the
reaction.
10
CA 02660069 2009-03-24
Upon forming the metal complex, it may be used to treat any of a number of
different types of nanomaterials, including particularly, nanotubes.
In one
embodiment, the nanomaterial may be "treated" by mixing it with the metal
complex,
typically in a solvent to form a solution. Any method of mixing the
nanomaterial and
the metal complex known in the art may be used in the present invention. The
term
"mixing," as used herein, means that the nanomaterial and the metal complex
are
brought into contact with each other in the presence of the solvent. "Mixing"
may
include simply vigorous shaking, or may include sonication for a period of
time of
about 10 min. to about 30 min.
A solvent may be used to disperse the nanonaterial and incorporate and treat
the nanomaterial with the metal complex. The solvent may be organic or aqueous
such as, for example, CHCI3, chlorobenzene, water, acetic acid, acetone,
acetonitrile, aniline, benzene, benzonitrile, benzyl alcohol, bromobenzene,
bromoform, 1-butanol, 2-butanol, carbon disulfide, carbon tetrachloride,
chlorobenzene, chloroform, cyclohexane, cyclohexanol, decalin, dibromethane,
diethylene glycol, diethylene glycol ethers, diethyl ether, diglyme,
dimethoxymethane, N,N-dimethylformamide, ethanol, ethylamine, ethylbenzene,
ethylene glycol ethers, ethylene glycol, ethylene oxide, formaldehyde, formic
acid,
glycerol, heptane, hexane, iodobenzene, nnesitylene, methanol, methoxybenzene,
methylamine, methylene bromide, methylene chloride, methylpyridine,
morpholine,
naphthalene, nitrobenzene, nitromethane, octane, pentane, pentyl alcohol,
phenol,
1-propanol, 2-propanol, pyridine, pyrrole, pyrrolidine, quinoline, 1,1,2,2-
tetrachloroethane, tetrachloroethylene, tetrahydrofuran, tetrahydropyran,
tetralin,
tetramethylethylenediamine, thiophene, toluene, 1,2,4-trichlorobenzene, 1,1,1-
trichloroethane, 1,1,2-trichloroethane, trichloroethylene, triethylamine,
triethylene
glycol dimethyl ether, 1,3,5-trimethylbenzene, m-xylene, o-xylene, p-xylene,
1,2-
dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2-dichloroethane,
N-
methy1-2-pyrrolidone, methyl ethyl ketone, dioxane, or dimethyl sulfoxide. In
certain
embodiments of the present invention, the solubilization solvent is a protic
solvent
and, in at least one embodiment, the solubilization solvent is water.
11
CA 02660069 2009-03-24
Of note, upon treatment of the nanomaterial with the metal complex, an
interaction occurs between the metal complex and nanomaterial. The interaction
is
a noncovalent bonding instead of covalent bonding. Therefore, the underlying
electronic structure of the nanomaterial and its key attributes are not
affected.
In one embodiment, the nanomaterial is treated with a metal salt such as, for
example, silver nitrate (AgNO3) in an aqueous solution. Generally, the silver
nitrate
is compatible with the nanomaterial, but not with the aqueous solvent, or vice
versa,
is compatible with the aqueous solvent, but not with the nanomaterial. Thus,
by
replacing the nitrate anions with an anion that will increase the
compatibility between
the nanomaterial and the aqueous solvent, the nanomaterial becomes "treated,"
meaning the resultant metal complex will be compatible and stable with both
the
nanomaterial and the solvent or matrix material. In one embodiment, an
inorganic
surfactant anion compound, such as an inorganic clay like sodium silicate
(montmorillonite), may be used to exchange the anion from a nitrate to a
silicate,
which has been found to be more compatible to the treatment of the
nanomaterial
and the aqueous solution.
Typically, treating the nanomaterials comprises the step of coating the metal
complex onto a surface of the nanomaterial by any manner known in the art.
Upon
treatment, the treated nanomaterial can be used for a variety of purposes as
described hereinbelow.
In one embodiment of the present invention, treated nanomaterial may
comprise an amount of metal complex by weight ratio of greater than zero and
less
than 1Ø The weight ratio is calculated as the weight of the coated
nanomaterials
minus the weight of uncoated nanomaterials divided by the weight of the
uncoated
nanomaterials. In the present invention it is preferable that the ratio is in
the range
of 20-30 wt%.
12
CA 02660069 2009-03-24
In yet another embodiment of the present invention, the treated nanomaterials
dispersed in solvent may not settle out even over a period of weeks. The
treated
nanomaterials can be isolated by filtering onto filter paper.
In another embodiment of the present invention, solid coated nanomaterial
may be obtained from solution by removing the solvent. That is, solid coated
nanomaterial can be obtained from the solutions of coated nanomaterial as
described above by removing the solvent by one of many standard procedures
well
known to those of ordinary skill in the art. Such standard procedures include
drying
by evaporation such as by evaporation under vacuum or evaporation with heat,
casting, precipitation or filtration and the like. A solvent for precipitating
solid coated
nanomaterials has a polarity that is opposite in the polarity of the metal
complexes.
For material obtained by methods of the present invention, the solid coated
nanomaterial is generally black in color with a uniform network of carbon
nanotubes.
Solid coated nanomaterial may be pulverized to produce a powder.
As an example of making treated nanomaterials, a silver complex as
described above, e.g., the silver(I) silicate complex, may be dispersed with
carbon
nanotubes in a solvent such as water. It will be appreciated that the silver
silicate
may be originally another silver-based salt, such as silver nitrate for the
initial
dispersion. The silver cation is absorbed onto the surface of the nanomaterial
and
the silicate, provided as, for example, sodium montmorillonite, is exchanged
with the
nitrate in an ion exchange process within the treatment solution. The silver
complexes attach (non-covalently bond) to the surface of the carbon nanotubes,
but
do not affect their electrical conductivity abilities. The result of this
mixing yields
carbon nanotubes coated with the silver based complex. The coated nanomaterial
can be isolated as a dispersion of the coated nanomateral in a solvent or it
may be
isolated as a solid coated nanomaterial. Such coated nanomaterials can then be
easily be dispersed in solvents, monomers, oligomers, polymers, various
hydrocarbon and/or inorganic matrices or the like, as described hereinbelow.
13
CA 02660069 2009-03-24
Upon forming the treated nanomaterials, these nanomaterials may then be
dispersed in a matrix material to form nanocomposites. That is, a
nanocomposite
comprises a matrix; and a nanomaterial treated with a metal complex and
dispersed
in the matrix. The metal complex contains a metal cation capable of being
adsorbed
onto a surface of the nanomaterial. The metal complex also contains an
inorganic
surfactant anion compatible with the matrix; and is devoid of any neutral
donor
ligands attached to the metal cation. Because of the inorganic surfactant
anion used,
any interactions between the metal complex and the nanomaterial, and between
the
metal complex and the matrix, are stabilized.
The terms "matrix" and "matrix material" are used interchangeably herein. Any
matrix material desired may be used in the present invention, provided the
metal
complex selected provides for desirable and favorable interactions between the
nanomaterial and the matrix material. Matrix material may include, but is not
necessarily limited to solvents (including the solvent used in treating the
nanomaterial), monomers, polymers, elastomers, thermoplastics, thermosets or
any
combinations or mixtures thereof. In one embodiment, the matrix is a solvent
or a
polymer. Where a solvent is used, such a solvent may be selected from the
group
consisting of water, methanol, methoxybenzene, methylamine, methylene bromide,
methylene chloride, methylpyridine, morpholine, naphthalene, nitrobenzene,
nitromethane, octane, pentane, pentyl alcohol, phenol, 1-propanol, 2-propanol,
pyridine, pyrrole, pyrrolidine, quinoline,
1,1,2,2-tetrachloroethane,
tetrachloroethylene, tetrahyd rofu ran , tetrahydropyran,
tetralin,
tetramethylethylenediamine, thiophene, toluene, 1,2,4-trichlorobenzene, 1,1,1-
trichloroethane, 1,1,2-trichloroethane, trichloroethylene, triethylamine,
triethylene
glycol dimethyl ether, 1,3,5-trimethylbenzene, m-xylene, o-xylene, p-xylene,
1,2-
dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2-dichloroethane,
methyl ethyl ketone, dioxane, acetic acid, acetone, acetonitrile, aniline,
benzene,
benzonitrile, benzyl alcohol, bromobenzene, bromoform, 1-butanol, 2-butanol,
carbon disulfide, carbon tetrachloride, chlorobenzene, chloroform,
cyclohexane,
cyclohexanol, decalin, dibromethane, diethylene glycol, diethylene glycol
ethers,
14
CA 02660069 2009-03-24
diethyl ether, diglyme, dimethoxymethane, N,N-dimethylfornnamide, ethanol,
ethylamine, ethylbenzene, ethylene glycol ethers, ethylene glycol, ethylene
oxide,
formaldehyde, formic acid, glycerol, heptane, hexane, iodobenzene,
mesitylene,or
dinnethyl sulfoxide. In one embodiment, the solvent is a protic solvent. In a
further
embodiment, the solvent is an aqueous solvent.
Where a polymer is used, it may be selected from inorganic or organic
polymers. Inorganic polymers may include, but are not limited to,
polysiloxanes,
polysilanes, polygermanes, polystannanes, polyphosphazenes, and combinations
thereof. Organic polymers may include, but are not limited to, polyolefins
(PO),
polyamides (nylons), polystyrenes (PS), ethylene-vinyl acetate copolymers
(EVA),
polyimides, polyurethanes (PU), poly(ethylene terephthalate) (PET), polyvinyl
chloride (PVC), polystyrenes (PS), poly(ethylene-co-vinyl acetate) (PEVA),
epoxies,
polyanilines, polythiophenes, cyanate esters, polycarbonates, and copolymers,
terpolymers, and mixtures thereof. In one embodiment, organic polymers
selected
from the group consisting of polystyrenes, polycarbonates, epoxies and
polyurethanes are preferred. In another embodiment, organic polymers selected
from the group consisting of polyesters, polyamides, and polyimides are
preferred.
In yet another embodiment, the preferred matrix material may be oligomers
selected
from the group consisting of polyols and prepolymers.
In a further embodiment of the invention, the nanomaterial may be dispersed
into the matrix material with other additives or materials. Such other
materials may
add desired properties beyond those added to the matrix material by the
dispersion
of the nanonnaterial. Such additives include, but are not necessarily limited
to, other
silicates, clays, ceramics, plasticizers, metal oxides, other nanomaterials,
and other
carbon based materials such as carbon black or graphite, or combinations of
these.
Upon the addition of these other additives, other nanocomposites may be
possible.
Where ceramics are used, such ceramics may include, but are not necessarily
limited to alumina, zirconia, carbides, nitrides, borides, silicides and
combinations
thereof.
CA 02660069 2009-03-24
A further embodiment of the present invention comprises a method for
making a nanocomposite comprising a matrix and a nanomaterial, wherein the
nanomaterial is compatible with the matrix upon treatment thereof. The method
comprises treating the nanomaterial with a metal complex, the metal complex
containing a metal cation and an inorganic surfactant anion. The metal cation
is
adsorbed onto a surface of the nanomaterial. The surfactant anion is
compatible with
the matrix and the metal complex such that no neutral donor ligand is
required. The
inorganic surfactant anion of the metal complex may, likewise, stabilize any
interactions between the metal complex and the nanomaterial, and/or any
interactions between the metal complex and the matrix. Other additives may
then
be added to the treated nanomaterial, if desired, and then the treated
nanomaterial
is dispersed into a matrix.
As described above, treating a nanomaterial may comprise coating the metal
complex onto a surface of the nanomaterial. There are several ways in which to
disperse the nanomaterial into the matrix.
For example one way to disperse the treated nanomaterial in the matrix is to
melt the matrix and mix the nanomaterial into the melted matrix. This is known
as
melt compounding. Alternatively, the treated nanomaterial may be dispersed by
solvating the matrix in one of the solvents described above and mixing the
nanomaterial into the solvated matrix. Still further, the treated nanomaterial
may be
dispersed by mixing the nanomaterial into a monomer of the matrix and
polymerizing
the matrix. All of these methods are generally known in the art for
mixing/dispersing
compounds.
Another method for making a nanocomposite comprising a matrix and a
nanomaterial includes the steps of coating the metal complex onto a surface of
the
nanomaterial and dispersing the nanomaterial in the matrix to make a
masterbatch
16
CA 02660069 2009-03-24
of the resultant nanocomposite. Then, additional nanomaterials may be
dispersed
into the masterbatch.
Yet a further embodiment for making a nanocomposite is to provide a
masterbatch of the resultant nanocomposite as described above and then to
further
disperse the masterbatch into another matrix. In this manner, it will be
appreciated
that new articles and compositions can be made that include the nanocomposites
of
the present invention having nanomaterials dispersed therein that have been
coated
with metal complexes of the present invention that enable the nanomaterial to
be
compatible with the matrix material into which they are dispersed.
Another embodiment of the present invention relates to the dispersion of
coated nanomaterial. Solid coated nanomaterial obtained as described above is
dispersed by mixing the solid coated nanomaterial with a matrix such as a
solvent,
oligomer and/or polymer. For dispersions of coated nanomaterials in solvents
the
term "mixing," as used herein for dispersion, means that the solid coated
nanomaterial and the solvent are brought into contact with each other.
"Mixing" for
dispersion may include simply vigorous shaking, or may include sonication for
a
period of time of about 10 min to about 30 min.
The dispersion solvent may be the same solvent as the solvent used in the
coating process or may be a different solvent. Accordingly, the solvent may be
organic, protic, or aqueous such as, for example, CHCI3, chlorobenzene, water,
acetic acid, acetone, acetonitrile, aniline, benzene, benzonitrile, benzyl
alcohol,
bromobenzene, bromoform, 1-butanol, 2-butanol, carbon disulfide, carbon
tetrachloride, chlorobenzene, chloroform, cyclohexane, cyclohexanol, decalin,
dibromethane, diethylene glycol, diethylene glycol ethers, diethyl ether,
diglyme,
dimethoxymethane, N,N-dimethylformamide, ethanol, ethylamine, ethylbenzene,
ethylene glycol ethers, ethylene glycol, ethylene oxide, formaldehyde, formic
acid,
glycerol, heptane, hexane, iodobenzene, mesitylene, methanol, methoxybenzene,
methylamine, methylene bromide, methylene chloride, methylpyridine,
morpholine,
17
CA 02660069 2009-03-24
naphthalene, nitrobenzene, nitromethane, octane, pentane, pentyl alcohol,
phenol,
1-propanol, 2-propanol, pyridine, pyrrole, pyrrolidine, quinoline, 1,1,2,2-
tetrachloroethane, tetrachloroethylene, tetrahydrofuran, tetrahydropyran,
tetralin,
tetramethylethylenediannine, thiophene, toluene, 1,2,4-trichlorobenzene, 1,1,1-
trichloroethane, 1,1,2-trichloroethane, trichloroethylene, triethylamine,
triethylene
glycol dimethyl ether, 1,3,5-trimethylbenzene, m-xylene, o-xylene, p-xylene,
1,2-
dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2-dichloroethane,
N-
methy1-2-pyrrolidone, methyl ethyl ketone, dioxane, or dimethyl sulfoxide. In
certain
embodiments of the present invention, the solvent may be a halogenated organic
solvent such as 1,1,2,2-tetrachloroethane, chlorobenzene, chloroform,
methylene
chloride, or 1,2-dichloroethane. In other embodiments, the solvent may be a
protic
solvent and, in at least one embodiment, the solvent is water.
Another embodiment of the present invention relates to coated nanomaterial
as provided herein dispersed within a host matrix. The host matrix may be a
host
polymer matrix or a host non-polymer matrix.
The term "host polymer matrix," as used herein, means a polymer matrix
within which the coated nanomaterial is dispersed. A host polymer matrix may
be an
organic polymer matrix or an inorganic polymer matrix, or a combination
thereof.
Examples of a host polymer matrix include polyamide (nylon), polyethylene,
epoxy
resin, polyisoprene, sbs rubber, polydicyclopentadiene,
polytetrafluoroethulene,
poly(phenylene sulfide), poly(phenylene oxide), silicone, polyketone, aramid,
cellulose, polyimide, rayon, poly(methyl methacrylate), poly(vinylidene
chloride),
poly(vinylidene fluoride), carbon fiber, polyurethane, polycarbonate,
polyisobutylene,
polychloroprene, polybutadiene, polypropylene, poly(vinyl chloride),
poly(ether
sulfone), poly(vinyl acetate), polystyrene, polyester, polyvinylpyrrolidone,
polycyanoacrylate, polyacrylonitrile, polyamide,
poly(aryleneethynylene),
poly(phenyleneethynylene), polythiophene, thermoplastic, thermoplastic
polyester
resin (such as polyethylene terephthalate), thermoset resin (e.g.,
thermosetting
18
CA 02660069 2009-03-24
polyester resin or an epoxy resin), polyaniline, polypyrrole, or polyphenylene
or a
combination thereof.
Further examples of a host polymer matrix include a thermoplastic, such as
ethylene vinyl alcohol, a fluoroplastic such as polytetrafluoroethylene,
fluoroethylene
propylene, perfluoroalkoxyalkane, chlorotrifluoroethylene,
ethylene
chlorotrifluoroethylene, or ethylene tetrafluoroethylene, ionomer,
polyacrylate,
polybutadiene, polybutylene, polyethylene,
polyethylenechlorinates,
polymethylpentene, polypropylene, polystyrene, polyvinylchloride,
polyvinylidene
chloride, polyamide, polyamide-imide, polyaryletherketone, polycarbonate,
polyketone, polyester, polyetheretherketone, polyetherimide, polyethersulfone,
polyimide, polyphenylene oxide, polyphenylene sulfide, polyphthalamide,
polysulfone, or polyurethane. In certain embodiments, the host polymer may
include
a thermoset, such as allyl resin, melamine formaldehyde, phenol-fomaldehyde
plastic, polyester, polyimide, epoxy, polyurethane, or a combination thereof.
Examples of inorganic host polymers include a silicone, polysilane,
polycarbosilane, polygermane, polystannane, a polyphosphazene, polysilicates,
or a
combination thereof.
More than one host matrix may be present in a nanocomposite. By using
more than one host matrix, mechanical, thermal, chemical, or electrical
properties of
a single host matrix nanocomposite are optimized by adding coated nanomaterial
to
the matrix of the nanocomposite material.
In one embodiment, using two host polymers is designed for solvent cast
epoxy nanocomposites where the coated nanomaterial, the epoxy resin and
hardener, and the polycarbonate are dissolved in solvents and the
nanocomposite
film is formed by solution casting or spin coating.
19
CA 02660069 2009-03-24
In a further embodiment of the invention, the coated nanomaterial of the
nanocomposite may be a primary filler. In this case, the nanocomposite may
further
comprise a secondary filler to form a multifunctional nanocomposite.
In this
embodiment, the secondary filler comprises a continuous fiber, a discontinuous
fiber,
a nanoparticle, a microparticle, a macroparticle, or a combination thereof. In
another
embodiment, the treated nanomaterial of the nanocomposite is a secondary
filler
and the continuous fiber, discontinuous fiber, nanoparticle, microparticle,
macroparticle, or combination thereof, is a primary filler.
It will be understood that the nanocomposites themselves can be used as a
host matrix for a secondary filler to form a multifunctional nanocomposite.
Examples
of a secondary filler include: continuous fibers (such as carbon fibers,
carbon
nanotube fibers, carbon black (various grades), carbon rods, carbon nanotube
nanocomposite fibers such as nylon fibers, glass fibers, nanoparticles (such
as
metallic particles, polymeric particles, ceramic particles, nanoclays, diamond
particles, or a combination thereof, for example), and microparticles (such as
metallic particles, polymeric particles, ceramic particles, clays, diamond
particles, or
a combination thereof, for example). In a further embodiment, the continuous
fiber,
discontinuous fiber, nanoparticle, microparticle, macroparticle, or
combination
thereof, is a primary filler and the coated nanomaterial is a secondary
filler.
A number of existing materials use continuous fibers, such as carbon fibers,
in a matrix. These fibers are much larger than carbon nanotubes. Adding coated
nanomaterial to the matrix of a continuous fiber reinforced nanocomposite
results in
a multifunctional nanocomposite material having improved properties such as
improved impact resistance, reduced thermal stress, reduced microcracking,
reduced coefficient of thermal expansion, or increased transverse or through-
thickness thermal conductivity. Resulting advantages of multifunctional
nanocomposite structures include improved durability, improved dimensional
stability, elimination of leakage in cryogenic fuel tanks or pressure vessels,
improved
through-thickness or in plane thermal conductivity, increased grounding or
CA 02660069 2009-03-24
electromagnetic interference (EMI) shielding, increased flywheel energy
storage, or
tailored radio frequency signature (Stealth), for example. Improved thermal
conductivity also could reduce infrared (IR) signature. Further existing
materials that
demonstrate improved properties by adding coated nanomaterial include metal
particle nanocomposites for electrical or thermal conductivity, nano-clay
nanocomposites, or diamond particle nanocomposites, for example.
In light of the foregoing, it will be appreciated that an article of
manufacture
comprising a polymer, a solution, a solid, a coated solid, or an insoluble
solid
containing a metal complex, a nanomaterial or a nanocomposite of the present
invention as set forth herein can be produced. Such articles of manufacture
include,
but are not limited to, for example, epoxy and engineering plastic composites,
filters,
actuators, adhesive composites, elastonner composites, materials for thermal
management (interface materials, spacecraft radiators, avionic enclosures and
printed circuit board thermal planes, materials for heat transfer
applications, such as
coatings, for example), aircraft, ship infrastructure and automotive
structures,
improved dimensionally stable structures for spacecraft and sensors, reusable
launch vehicle cryogenic fuel tanks and unlined pressure vessels, fuel lines,
packaging of electronic, optoelectronic or microelectromechanical components
or
subsystems, rapid prototyping materials, fuel cells, medical materials,
composite
fibers, or improved flywheels for energy storage.
The following examples are presented to further illustrate various aspects of
the present invention, and are not intended to limit the scope of the
invention.
Example 1: This example is used to illustrate how a silver complex is
synthesized for use in coating nanomaterials.
Sodium dodecyl sulfate (SDS) (1.5 g, 5.0 mmol) was added by solid addition
to an aqueous solution (1.0 mL) of silver nitrate (0.85 g, 5.0 mmol) and
stirred at RT
for 10 min. Chloroform (10 mL) was added to dissolve the silver(I) dodecyl
sulfate.
21
CA 02660069 2009-03-24
The solution was filtered to remove the NaNO3. 4,4-bipyridine (0.78 g, 5.0
mmol)
was added to the filtrate and stirred for 30 minutes to yield a viscous
solution. The
solvent was removed under reduced pressure to yield an off-white solid
material that
is ready for use as a connptibilizer. Thermal gravimetric analysis (TGA) of
the
compatibilizer demonstrated thermal stability with the loss of 4,4-bipyridine
and
dodecyl sulfate at ca. 220 C. The molecular composition was confirmed by 1H
and
13C NMR and elemental analysis.
Example 2: The following example is used to illustrate the treatment of
MWNT with the silver complex.
The MWNT (Baytubes C 150 P) used in this study were supplied by Bayer
MaterialScience AG. It will be understood, however, that any nanomaterials,
including other nanotubes, made by other methods/suppliers known to one of
skilled
in the art in light of the present disclosure may be used. They had a 95%
purity,
outer mean diameter of 13-16 nm and a length of 1-10 pm. The MWNT were used
as received/without any purification.
Sonication was performed with the SONICATOR 3000 supplied from
Misonix, Inc. The sonicator was equipped with a 3/4" horn and operated at a
control
setting of 6.5 (approximately 40 W).
An embodiment of the present invention comprises the formation of solutions
of coated nanotubes, and solid compositions thereof. It is preferable to coat
the
carbon nanotubes with the silver complex in situ. For example, 2.0 g of carbon
nanotubes were dispersed in 200 mL of chloroform by sonicating for 5 minutes.
In a
separate flask, silver nitrate (0.16 g) was dissolved in 0.5 mL of water and
SDS (0.27
g) was added and mixed. Chloroform (20 mL) was added to dissolve the complex
and this solution was added to the dispersed carbon nanotubes and sonicated
for 5
additional minutes. 4,4-bypyridine (0.13 g) in chloroform (20 mL) was added to
the
carbon nanotubes/AgNO3/SDS/chloroform solution and sonicated for an additional
5
77
CA 02660069 2009-03-24
minutes. Sonication is terminated and this solution is stable for weeks
without
settling out. The treated carbon nanotubes can be isolated by vacuum
filtration to
yield a black solid that weighs 2.48 g after drying at 70 C for 10 h. The
ratio (w/w)
of the silver complex to carbon nanotubes is calculated as 0.24. This same
ratio is
obtained in further experiments where the addition of silver complex is in
excess of
the amount needed to produce a 0.24 weight ratio.
Example 3: This example illustrates the dispersion of coated nanotubes.
The isolated coated nanotubes above can be re-dispersed in organic solvents
by mixing the coated nanotubes in the solvent. For example, 3.0 mg of coated
nanotubes are added to 1 mL of chloroform. The mixture was sonicated at room
temperature for about 10 seconds. The resulting solutions are stable and do
not
settle, even after weeks.
Example 4: This example is used to illustrate the formation of an
epoxy/nanotube composite using treated nanotubes.
Dispersion of Treated Nanotubes into Epoxy Resin: Treated nanotubes can
be dispersed into epoxy resins by addition of the treated nanotubes into
either
component of a two component epoxy resin system. Chloroform is added to the
nanotube containing component in the amount needed to sufficiently lower the
viscosity so that sonication is possible. The nanotube component is sonicated
and
the chloroform is removed under vacuum. An equal portion of the non-nanotube
component is added and the mixture is mixed for 1 min using a propeller blade
mixer. The mixture is poured into a mold and allowed to cure overnight to
yield an
epoxy/nanotube composite. Composite with varied loadings of treated nanotubes
and untreated carbon nanotubes were prepared (1.0, 0.5, 0.1 and 0.01 wt%
carbon
nanotubes) and evaluated by microscope and it was determined that the treated
nanotubes provided composite material with superior dispersion properties.
23
CA 02660069 2009-03-24
Example 5: This example is used to illustrate the dispersion of treated
nanotubes into a Nylon-12.
Coated nanotubes were dispersed in nylon-12 at 3 wt% and 6 wt% carbon
nanotubes using the following procedure. Dry blends of coated carbon nanotubes
(20 wt % coated with silver(I)-4,4-bipyridine dodecyl sulfate) and nylon 12
powder
were prepared and vacuum dried for 16 h under reduced pressure at 70 C.
Control
batches were prepared using identical experimental conditions, however,
uncoated
carbon nanotubes were tested. All blends were then mixed for 2 minutes at 60
rpm
at 190 C using Volkume Brabender Mixer fitted with intermix type rotors. The
resultant nanocomposites were cut into pieces, vacuum dried at 70-80 C/29 in
Hg/16h then compression molded into 4' x 4' x 0.036' plaques @ 180 C. Volume
resistivity was measured across the thickness using 3/8" diameter electrodes
coated
with conductive silver paste. Ohm readings were taken with a Fluka model 16
digital
multimeter. The volume resisitivity (Ohm-cm) recorded were 2.10E+06, 1.38E+03,
1.20E+08, and 1.13E+08 for the resulting nanocomposites containing 3.0 wt%
coated nanotubes, 6.0 wt% coated nanotubes, 3.0 wt% uncoated nanotubes and 6.0
wt% uncoated nanotubes respectively.
Example 6: This example is used to illustrate the dispersion of treated
nanomaterials, namely multi-walled carbon nanotubes, into an aqueous solvent.
Approximately 4.0 g of carbon nanotubes were sonicated in 200 mL of water
for approximately 2 to 5 minutes. About 0.4 g of silver nitrate dissolved in
about 10
mL of water was added to the carbon nanotubes and sonication was continued for
about 2 to 5 minutes. 1-3 equiv (4-12 g) of sodium montmorillonite in 100 mL
was
added, and the solution was sonicated for another 5 minutes. The resultant
product
yielded a stable dispersion of silver silicate (montmorillonite)-coated
nanotubes in
water.
24
CA 02660069 2016-02-18
=
Example 7: This example is used to illustrate another embodiment of the
dispersion of treated nanomaterials into an aqueous solvent.
Approximately 4.0 g of carbon nanotubes were sonicated in 200 mL of water
for approximately 2 to 5 minutes. About 0.4 g of copper nitrate dissolved in
about 10
mL of water was added to the carbon nanotubes, and sonication was continued
for
about 2 to 5 minutes. 1-3 equiv (4-12 g) of sodium montmorillonite in 100 mL
was
added, and the solution was sonicated for another 5 minutes to yield a stable
dispersion of copper silicate (montmorillonite)-coated nanotubes in water.
Example 8: This example is used to illustrate the formation of a treatment of
carbon nanomaterials (MWNT) in an aqueous solution.
The aqueous material obtained from Examples 6 and 7 were cast onto a
glass substrate and dried overnight under ambient conditions. The resulting
film
showed no signs of cracking, excellent lubricity, and a surface resistivity of
2.4 X 106
ohm/sq.
An embodiment of the present invention include methods for incorporating
treated nanomaterial into host polymer matrix. This includes, but are not
limited to:
(i) in-situ polymerization of monomer(s) of the host polymer the presence of
coated
nanomaterial; (ii) mixing both coated nanomaterial and host matrix in a
solvent
system; or (iii) mixing coated nanomaterial with a host polymer melt.
Other embodiments of the present invention will be apparent to those skilled
in the art from a consideration of this specification or practice of the
embodiments
disclosed herein. However, the foregoing specification is considered merely
exemplary of the present invention and the scope of the claims should not be
limited
by the preferred embodiments set forth in the examples, but should be given
the
broadest purposive construction consistent with the description as a whole.
