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Description  |
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BACKGROUND OF THE INVENTION
This application is a continuation-in-part of U.S. application Ser. No.
158,478, filed Feb. 22, 1988, of Stuart I. Yaniger and Randy E. Cameron,
and assigned to the same Assignee as the present application.
This invention relates to the production of electrically conductive polymer
materials and is particularly concerned with the solution blending of
conductive polyaniline and conductive polyaniline derivatives, with
maleimide systems, particularly bismaleimide, to produce cured maleimide
materials having electrical conductivity, without decreasing the
mechanical properties of the maleimide component.
The free-base form of polyaniline is believed to comprise subunits having
the formula:
##STR1##
where n is between 0 and 1. The oxidation state of polyaniline referred to
as "emeraldine" is believed to have a value of n of about 0.5.
This free-base form of polyaniline is an electrical insulator. Reaction of
emeraldine free-base with protonic acids of the form HX, where X is, for
example, Cl, causes the polymer to undergo an insulator to conductor
transition, as disclosed in A. G. MacDiarmid, ct al, Mol. Cryst. Liq.
Cryst. 121, 173 (1985). Conductive polyaniline of this type has been
employed in batteries as disclosed, for example, in French Patent No.
1,519,729.
However, a number of difficulties have been encountered with the prior art
materials noted above. Thus, the conductive polyaniline acid salts are,
with a few exceptions, insoluble in most solvent media. None of the
polyanilines can be melted. The emeraldine free-base and the conductive
forms thereof noted above tend to form powders on removal of the solvent.
With some effort, films can be cast; however, they are quite fragile and
brittle, easily crumbling to form a powder. The conductive acid salts lose
their conductivity when exposed to liquid water. This loss is due to
deprotonation. The conductivity loss is reversible; treatment of the
deprotonated material with protic acids restores the conductivity.
Further, conductive regions in an insulating matrix tend toward diffusion.
For example, if one makes a conductive trace of polyaniline acid salt on a
substrate of emeraldine free-base, the trace remains spatially stable for
only a short time, eventually spreading out until the substrate has a
constant conductivity throughout.
Some of these problems were addressed in U.S. applications Ser. No. 920,474
filed Oct. 20, 1986, of S. I. Yaniger, and Serial No. 013,305 filed
February 11, 1987, of S. I. Yaniger, et al, both assigned to the same
assignee as the present application. In these applications, it is
disclosed that Lewis acids, for example, alkylating agents, can be used to
make the insulating emeraldine free-base into a conductive polymer salt.
Use of proper Lewis acids resulted in conductive polyanilines with the
Lewis acid as a side chain. These derivatized polyanilines are more water
stable and processable than the prior art emeraldine acid salts.
Additionally, no diffusion between "doped" conducting and "undoped"
insulating regions was observed.
Thus, in the above U.S. application, Ser. No. 920,474, a base-type
non-conductive polymer, such as polyaniline, can be reacted with, for
example, methyl iodide, to form an electrically conductive polymer in
which the methyl group is covalently linked to the nitrogen atoms of the
polymer.
In the above U.S. application, Ser. No. 013,305, emeraldine free-base can
be reacted with reagents of the form RSO.sub.2 Cl, e.g., tosyl chloride,
to form an electrically conductive polymer in which the --SO.sub.2 R
groups are covalently linked to the nitrogen atoms of the polymer.
U.S. application Ser. No. 158,477 filed Feb. 22, 1988, of S. I. Yaniger and
R. E. Cameron and assigned to the same assignee as the present
application, discloses reaction of a base-type non-conductive polymer,
such as polyaniline, with an anhydride, such as tosylic anhydride or
benzophenone tetracarboxylic dianhydride, and forming an electrically
conductive polymer in which the --SO.sub.2 R and --COR groups are
covalently linked to the nitrogen atoms of the conductive polymer.
In general, however, the conductive polymers of the above applications tend
to be brittle, resulting in inferior mechanical properties.
It would be desirable to blend the relatively brittle conducting polymer
with a flexible polymer to form a blend having both the desired electrical
properties and good flexibility.
To achieve high electrical conductivity the proportion of conductive
polymer to non-conductive polymer in the blend must be relatively high
(e.g., greater than 50%) in order for charge to be transferred effectively
between polymer chains. Unfortunately, at high polyaniline loadings, the
blend materials tend to phase separate, that is, the polyaniline
aggregates into clumps within the non-conductive polymer matrix. These
clumps are separated by the matrix material, and the blend thus is an
insulator. Further, the mechanical properties of the material suffer upon
phase separation. It would be desirable to form blends where the
polyaniline is dispersed evenly on a molecular level at all loadings, to
thus form a conductive polymer blend.
In the above U.S. application Ser. No. 158,478, of which the present
application is a continuation-in-part, there is disclosed a conductive
polymer blend formed by first reacting a base-type non-conductive polymer
containing carbon-nitrogen linkages, such as polyaniline, with a carbonyl
anhydride, such as 3,3',4,4'-benzophenone tetracarboxylic dianhydride, to
form a conductive polymer containing polyimide-like groups covalently
linked to nitrogen atoms of the base-type polymer, mixing such conductive
polymer with non-conductive polyimide in a suitable solvent, removing the
solvent, and forming a conductive continuous phase blend of the polyimide
and the conductive polymer. However, unless the polyimide has a very low
melt temperature, the conductive polymer-polyimide blends of the above
application are not melt processible and are more useful for making
conductive films or fibers than large parts, in which a meltable resin is
necessary. In order for a conductive polyaniline to be melt processed or
cured with another resin system, such polyaniline must be able to
withstand the curing temperature of the other resin system.
In U.S. application Ser. No. 226,484, filed Aug. 1, 1988, by R. E. Cameron,
and assigned to the same assignee as the present application, there is
disclosed conductive multisulfonic acid derivatives of polyaniline which
are highly thermally stable.
Examples of other conductive polymer mixtures are set forth in the
following patents.
U.S. Pat. No. 4,526,706 to Upson, et al, discloses a conductive latex
coating composition useful in forming conductive layers which comprises a
latex having as a dispersed phase in water hydrophobic polymer particles
having associated therewith a polyaniline salt semiconductor. The
preferred polymer particles are polyurethane particles, but other polymer
particles, such as various acrylate polymers, can be employed.
U.S. Pat. No. 3,766,117 to McQuade discloses a method of preparing an
electrodepositable solution of a polyamic acid in an organic solvent, for
use in electrodepositing a polyamic acid coating on an electrically
conducting substrate. The method comprises preparing a solution of an
aromatic polyamic acid in an organic solvent, adding to the polyamic acid
solution a base, such as ammonia or an organic amine, e.g., an
alkanolamine, and adding water to the base-modified polyamic solution to
precipitate at least a portion of the polyamic acid to form a stable
electrodepositable dispersion of polyamic acid. A coating of polyamic acid
is then electrodeposited from the medium onto a conductive substrate, and
the coating is then cured to a polyimide to form an insulation coating.
An object of the present invention is the provision of improved
electrically conductive polymer materials of the class of conductive
polyaniline blended with an imide other than the polyimides of the above
U.S. application Ser. No. 158,478.
Another object is to provide conductive polymer materials having improved
flexibility, mechanical properties, and thermal stability in the form of a
continuous phase blend of a conductive polymer, e.g., conductive
polyaniline, and a maleimide, which is capable of melt processing and is
particularly applicable for production of large parts.
A still further object is to render imides, particularly bismaleimides,
conductive by doping with a conductive polymer, such as conductive
polyaniline, to produce an easily processable, highly thermally stable
conductive polymer blend.
A still further object is to provide novel procedure for blending
polyaniline in the solution phase with a maleimide such as bismaloimide,
whereby on removal of the solvent, the resulting polymer blend can be
processed to yield strong adhesive conductive resins.
SUMMARY OF THE INVENTION
The above objects are achieved and a conductive polymer blend is produced
according to the invention by solution blending in a suitable solvent a
mixture of (a) an electrically conductive polymor containing
carbon-nitrogen linkages, particularly a conductive polyaniline or a
polyaniline derivative, and (b) a maleimide, particularly a bismaleimide,
removing the solvent, and forming a continuous phase blend of the
conductive polymer and the maleimide, as by heating to cure the maleimide.
The invention is carried out by first reacting a base-type non-conductive
polymer containing carbon-nitrogen linkages, particularly from the family
of the polyanilines, with a cation donor compound capable of covalently
binding to the nitrogens of the polymer, such as a carbonyl or sulfonyl
anhydride, to thereby form an electrically conductive polymor, e.g., a
derivatized polyaniline having an organic or inorganic group covalently
linked to nitrogen atoms of the base-type polymer, e.g., as described in
the above U. S. application Ser. No. 158,477 of S. I. Yaniger, et al.
The conductive polymer so formed is mixed with a maleimide, particularly a
bismaleimide, e.g., in certain ranges of proportions as described
hereinafter, in a suitable solvent, such as N-methyl pyrrolidone (NMP), to
form a melt processible blend of the two components in the solution phase.
Upon removal of the solvent, the mixture forms a continuous phase blend,
the blended materials resulting in an electrically conductive resin which
is strong and can be used as the matrix material in a non-metallic
conductive composite, e.g., for fabrication of large parts, such as
aircraft components. The blends of the present application are
thermosetting in that they melt and cure to an insoluble part.
Another important advantage of the conductive polyaniline blends of the
present application is that the bismaleimide thereof cures without giving
off volatiles and without decomposing the polyaniline, whereas the curing
of the polyimide in the conductive polyaniline-polyimide blends of above
U.S. application Ser. No. 158,478 evolves volatiles.
If desired, in the above procedure, the electrically conductive polymer,
e.g., conductive polyaniline, can be formed in situ, during solution
blending with the maleimide component, by incorporating in the solvent
solution the non-conductive polymer, e.g., polyaniline, and the cation
donor compound for reaction with such non-conductive polymer, to form the
resulting conductive polymer, in solution with the maleimide component.
Thus, the present invention discloses a technique for increasing the
electrical conductivity of a maleimide, particularly bismaleimide, without
materially adversely affecting, or without decreasing, the mechanical
properties thereof.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
Conductive Polymer Component
In preferred practice, a base-type non-conductive polymer containing
carbon-nitrogen linkages is first reacted with a cation donor compound to
form a polymer salt in which a covalent bond is formed between the
nitrogens of the polymer and such donor cation.
A preferred form of non-conductive polymer can be represented as follows:
##STR2##
where A is a carbon-containing group, such as aryl, particularly the
benzene ring, as in polyaniline, and including naphthyl and biphenyl, and
substituted benzene, naphthyl or biphenyl groups, such as the alkyl
substituted derivatives, e.g., 2-methyl biphenyl, butyl naphthalene,
2-methyl aniline, and aryl substituted derivatives, e.g., beta phenyl
naphthalene and beta tolyl naphthalene; and y is an integer ranging from
about 1 to about 1,000, e.g., about 10 to about 100.
Thus, the above non-conductive polyaniline family of polymers can be
further characterized as consisting of polyaniline, its naphthyl and
biphenyl derivatives, and alkyl and aryl substituted polyaniline and its
alkyl and aryl substituted naphthyl and biphenyl derivatives.
The preferred non-conductive polymer containing carbon-nitrogen linkages is
the basic polymeric starting material, polyaniline emeraldine free-base
(PFB).
Other polymeric starting materials can include other non-conductive
base-type polymers containing carbon atoms linked to nitrogen, such as
cyanogen polymer containing the recurring unit:
##STR3##
The starting materials of the invention can also include non-conductive
mixtures and blends of the above polymers, and copolymers of the above
polymers and other polymers, such as a blend of polyaniline and
polymethylmethacrylate, and polymer alloys, such as
polybenzimidazole-polyimide alloys, containing carbon-nitrogen groups.
Thus, the term "non-conductive polymer" as employed herein is intended to
denote any of the above homopolymer or copolymer materials.
The invention will be described hereinafter, however mostly in terms of the
use of the preferred non-conductive free-base polyaniline as polymeric
starting material. This is a high polymer having a molecular weight of the
order of 50,000 to 80,000. Lower molecular weight forms of polyaniline can
also be employed, such as an oligomer of polyaniline containing 8
sub-units and having a molecular weight of about 800 to 900.
The non-conductive polymer e.g.. polyaniline, can be reacted with any
dopant which is effective to increase the electrical conductivity of the
polymer. Thus, for example, the free-base polyaniline can be reacted with
protonic acids, such as HX, where X is a halogen, such as Cl, to convert
the insulator to a conductor, as disclosed in the above MacDiarmid
reference.
However, the preferred conductive polymers are those prepared by reacting
the non-conductive polymer containing carbon-nitrogen linkages, such as
polyaniline, with a cation donor compound capable of covalently binding to
the nitrogens of such polymer to form an electrically conductive polymer.
Thus, the resulting conductive polymer has an organic or inorganic group
covalently linked to nitrogen atoms of the polymer and an anion associated
with such nitrogen atoms to form a polymer salt.
Such conductive polymers and their method of formation are described in the
above-noted applications. Thus, for example, the free-base polyaniline can
be treated and reacted with an R.sup.+ donor compound, such as RX, R.sub.3
OX, R.sub.2 SO.sub.4, R'SO.sub.2 Cl, or R.sub.3 "SiQ, where R, R'SO.sub.2
or R.sub.3 "Si is a group which readily forms a covalent bond with
nitrogen, and wherein R, R' and R" each can be alkyl containing from 1 to
20 carbon atoms, e.g., methyl, ethyl and the like, and aryl, e.g.,
p-toluene sulfonyl (tosyl), benzyl, tolyl, xylyl, and other aromatic
moieties, and X is an anion such as halogen, e.g., Cl.sup.-, I.sup.- or
Br.sup.- ; PF.sub.6.sup.-, SbCl.sub.6.sup.-, and substituted and
unsubstituted benzene sulfonate, and the like, and Q is a halogen, such as
Cl. The above reaction forms a conductive polymer salt.
Thus, the reactant which forms a covalent chemical bond with the nitrogen
of the polyaniline free-base or equivalent polymer noted above, can be,
for example, one of the above R.sup.+ donor compounds, such as an alkyl
halide, wherein the alkyl group can contain from 1 to 20 carbon atoms,
such as methyl iodide, or dimethylsulfate.
The reaction for converting the base-type non-conductive polymer to a
conductive polymer can be represented as follows, where, for example, RX
is the R.sup.+ donor compound:
##STR4##
where A and y are as defined above.
According to another preferred embodiment, as disclosed in the above U.S.
application Ser. No. 158,477, base-type non-conductive polymers containing
carbon-nitrogen linkages, particularly from the family of polyaniline, can
be converted to conductive polymers by reacting the non-conductive polymer
with an anhydride, such as R--SO.sub.2 --O--SO.sub.2 R', R--CO--O--CO--R',
or R--CO--O--SO.sub.2 R', or mixtures thereof, where R and R' are alky or
aryl, e.g., tosylic anhydride, benzophenone tetracarboxylic dianhydride,
or o-sulfobenzoic anhydride, according to the general reaction shown
above, and forming an electrically conductive polymer in which the
So.sub.2 R and COR groups are covalently linked to the nitrogen atoms of
the conductive polymer and the anion of the conductive polymer is the
SO.sub.3 R' or O.sub.2 CR' group.
According to still another preferred embodiment as disclosed in above U.S.
application Ser. No. 226,484, filed Aug. 1, 1988, by R. E. Cameron,
base-type non-conductive polymers containing carbon-nitrogen linkages,
particularly from the family of polyaniline, are converted to conductive
polymers of high thermal stability, by reacting the non-conductive polymer
with a multiprotic acid in the form of an aromatic multisulfonic acid,
e.g., having the formula R(SO.sub.3 H).sub.n, where R is aryl, such as
benzene or naphthalene, or their substituted derivatives, and n is an
integer of at least 2, preferably 2 to 4, or mixtures thereof, such as
m-benzene disulfonic acid, to form a polymer salt in which the --SO.sub.3
H groups are covalently linked to the nitrogens of the polymer through thc
hydrogen bond.
The molar proportions of cation donor compound to non-conductive, e.g.,
nitrogen-containing polymer free-base, can be varied but is sufficient to
increase the electrical conductivity of the polymer. Thus, for example, in
the case of the above donor compounds RX, R.sub.3 OX, R.sub.2 SO.sub.4,
R'SO.sub.2 Cl and R.sub.3 41 SiQ and the anhydrides, the molar proportions
of donor compound to nitrogen-containing polymer can range from about 0.01
to about 2 cation groups, e.g., SO.sub.2 R.sup.+ or COR.sup.+ groups in
the case of the anhydride, per nitrogen, and in the case of polyaniline,
such molar proportions can range from about 0.01 to about 8, per polymer
repeat unit. Where an aromatic multisulfonic acid is employed as cation
donor compound, a range of proportions of about 1/16 to about 2 moles of
multisulfonic acid per nitrogen of each polymer unit is employed and, i
the case of polyaniline, from about 1/8 to about 2 moles of multisulfonic
acid, for every 2 aniline units in the polyaniline chain.
The reaction can be carried out as a heterogeneous reaction wherein the
polymer starting material is not dissolved but is reacted directly with
the cation donor compound, e.g., anhydride, or the polymer starting
material, such as polyaniline non-conductive free-base, can be dissolved
in a suitable solvent which does not react irreversibly with such donor
compound, e.g., N-methyl pyrrolidone, dimethylsulfoxide (DMSO),
dimethylformamide (DMF), formic acid, dimethylacetamide (DMAC),
acetonitrile, tetrahydrofuran (THF), and pyridine.
The reaction is generally carried out at about ambient or room temperature,
e.g., 20.degree.-25.degree. C., or at higher or lower temperatures.
The rate of reaction can range widely, depending on the particular cation
donor compound reactant employed. Thus, the reaction rate can range from
almost instantaneous to several hours or longer.
The conductivity of the resulting conductive polymers, e.g., conductive
polyaniline, can be varied by reducing or increasing the number of
covalently linked side chains on the nitrogen atoms, as by controlling the
degree of completeness of the reaction and/or by varying the types of
cation donor compound employed in producing such side chains on the
polymer.
The disclosures of the above applications and the MacDiarmid reference are
incorporated herein by reference with respect to the conductive polymer
component of the present invention and its method of preparation.
Maleimide Component
The maleimide component which is blended with the above conductive polymer
according to the invention can have a single terminal maleimide unit but
is preferably a bismaleimide capped at opposite ends of the molecule with
a maleimide unit. The maleimide component can be in the form of a monomer
or an oligomer, preferably a bismaleimide terminated oligomer.
Examples of maleimide components which can be employed according to the
invention are as follows:
##STR5##
where m is an integer of from 1 to about 10, preferably 1 to about 4.
The BMI (bismaleimide) of formula III is known and can be made by reacting
1,3 bis (3-aminophenoxybenzene (APB)) and two units of MI (maleimide).
The BMI of formula IV is known and can be made by reacting 10 units of APB
and 10 units of benzophenonetetracarboxylic dianhydride (BTDA) capped by 2
units of MI.
The BMI of formula V can be made in known manner by reacting 10 units of
APB and 10 units of the anhydride marketed as 6FDA and having the formula:
##STR6##
capped by 2 units of MI.
Examples of additional BMI's are as follows:
##STR7##
The conductive polymer can be blended in a wide range of proportions with
non-conductive maleimide component, generally ranging from about 1 to
about 99% conductive polymer to 1 to about 99% non-conductive maleimide
component, e.g., bismaleimide, by weight of the mixture. The blend forming
the conductive film is the same as that noted above in preparing the
solutions of the blends. The blended polymer also has the good mechanical
properties of the maleimide component while having the good electrical
conductivity properties of the conductive base-type polymer, such as
conductive polyaniline. The continuous single-phase blends of the
conductive polymer and non-conductive maleimide component produced
according to thc invention do not separate out upon forming a film from
the blend
Further, upon removal of solvent, the resulting polymer blend can be melt
processed to yield strong adhesive resins.
Instead of forming a blend of the two components and the blend used to form
a coating, the conductive polymer and maleimide component blend can be
processed to a powder. This can be achieved, e.g., by blending the
non-conductive polymer, e.g., polyaniline, in solvent solution, e.g., NMP,
with maleimide component, particularly bismaleimide, and adding a cation
donor compound, such as benzene disulfonic acid for reaction with the
polyaniline to form conductive polymer. Thc resulting blend of both
components is precipitated out of solution by adding a precipitating
agent, such as hexane, toluene, or a mixture thereof, to the solution
blend. The precipitate can be filtered, and the resulting powder can be
pressed or molded into a thermoset part and cured of elevated temperature.
EXAMPLE 1
10 grams of PA (polyaniline) emeraldine free-base is dissolved into 250 ml
of NMP. To this solution is added 10 grams of the BMI of formula III
above. 6.5 grams of m-benzene disulfonic acid is added to the resulting
solution. Thc solution turns green. This solution contains about 50% of
conductive PA and about 50% of the BMI, by weight of the mixture.
The NMP is evaporated from the resulting solution or blend, and a film is
cast from the resulting conductive PA and BMI blend on a glass substrate.
The resulting film is heated at 180.degree. C. in air for 3 hours. The
cured film is electrically conductive and strong.
EXAMPLE 2
Thc solution or blend of conductive PA and BMI is formed as in Example 1.
Such solution is added dropwise to 500 ml of a 50--50 mixture of
hexane-toluene.
A green precipitate is formed, which is filtered from the reaction mixture.
The filtered precipitate is washed with excess hexane. The resulting dry
powder can then be pressed into pellets or parts. Such compressed pellets
or parts are cured by heating in air, argon or nitrogen at 180.degree. C.
for 4 hours. Since the BMI melts prior to curing at 180.degree. C., the
resulting electrically conductive parts have good mechanical properties.
The table below shows thc relationship between time of curing and
conductivity, for curing of the compressed pellets.
TABLE
______________________________________
ELECTRICAL
TIME OF CURING (HOURS)
CONDUCTIVITY (S/cm)
______________________________________
0 10.sup.-1
1 10.sup.-2
2 10.sup.-2.5
31/2 10.sup.-2.5
______________________________________
The above table shows that there is an initial decrease in conductivity
during the first 2 hours of curing, but once the material has cured, e.g.,
after about 3 hours, there is no longer any further drop in electrical
conductivity, as shown by the same value of conductivity for 31/2 hours of
curing as for 2 hours of curing. This shows that although there is an
initial drop in electrical conductivity of the resin blend, e.g., due to
binding of the BMI to the polyaniline amine groups, following curing, the
cured resin is still conductive and the electrical conductivity remains
constant. This indicates that the conductive polyaniline of the blend does
not decompose during or after curing.
If a higher electrical conductivity for the cured resin blend is desired, a
larger proportion of the conductive polyaniline polymer is employed in the
blend of conductive polymer and BMI, e.g., 75% conductive polyaniline and
25% BMI, by weight of the mixture.
EXAMPLE 3
The procedure of Example 1 is followed except employing o-sulfobenzoic
anhydride or p-toluenesulfonic anhydride, respectively, in place of
m-benzene disulfonic acid and in the same amount as the latter cation
donor compound for the PA.
Results similar to Example 1 are obtained.
EXAMPLE 4
The procedure of Example 1 is carried out using isopropyl iodide or
CH.sub.3 C.sub.6 H.sub.4 SO.sub.2 Cl, respectively, as cation donor
compound for the PA in place of m-benzene disulfonic acid, and in the same
amount thereof.
Results similar to Example 1 are obtained.
EXAMPLE 5
The procedure of Example 1 is followed except employing dimethyl sulfate in
the same amount as the m-benzene disulfonic acid.
Results similar to Example 1 are obtained.
EXAMPLE 6
The procedure of Example 1 is carried out except using the hydrogen ion
form of Nafion, a multisulfonic acid derivative of perfluorinated polymer,
marketed by DuPont, instead of m-benzene disulfonic acid and in the same
amount.
Results similar to Example 1 obtained.
EXAMPLE 7
The procedure of Example 1 is carried out, except using the BMI of formula
IV above and in the same amount as the BMI of formula III.
Results similar to Example I are obtained.
EXAMPLE 8
The procedure of Example 1 is carried out, except using the BMI of formula
V above and in the same amount as thc BMI of formula III.
Results similar to Example I are obtained.
EXAMPLE 9
The procedure of Example 1 is repeatcd, except using 5 grams of PA
free-base and 15 grams of the BMI component to form a solution blend
containing about 25% of conductive PA and about 75% of the BMI, by weight
of the mixture.
The electrically conductive polymer blends of the invention have utility in
the production of conductive composites, electronic components, electrical
conductors, electrodes, batteries, switches, electrical shielding
material, resistors, capacitors, and the like.
From the foregoing, it is seen that the invention provides a novel class of
conductive polymer materials which can be readily cast into tough,
flexible conductive films, by solution blending conductive, preferably
nitrogen-containing, polymers, such as conductive polyaniline, with a
maleimide component, particularly a bismaleimide. The resulting resin
blend increases the electrical conductivity of the maleimide component
without decreasing its mechanical integrity. The result is a conductive
resin of superior strength, toughness, flexibility and processibility. Due
to the melting followed by curing of the BMI when blended with the
conductive polyaniline, the conductive blend can be melted and cured
without the evolution of volatiles. No polyaniline decomposition is seen
with these materials.
While particular embodiments of the invention have been described for
purposes of illustration, it will be understood that various changes and
modifications within the spirit of the invention can be made, and the
invention is not to be taken as limited except by the scope of the
appended claims.
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