Electrically conductive composites of polyacetylene and high-nitrile resins and method thereof

An electrically conductive composite comprising conductive polyacetylene moiety, a nonconductive high nitrile resin, and a dopant. The high nitrile resin further comprises at least nitrile monomers or comonomers and optionally copolymerized with comonomers of mono-ethylenically unsaturated monomers and conjugated diolefins and further optionally containing an elastomeric component. The invention further includes a process for producing an electrically conductive composite comprising: PA1 (1) impregnating a high nitrile resin with a Zeigler type catalyst comprising an alkyl aluminum compound and alkyl, alkyl halide, halide, oxyhalide or alkoxide of Group IVA and VA metals, PA1 (2) exposing the impregnated high nitrile resin with an alkyne under polymerization conditions whereby polymerization occurs to form a polyacetylene/nitrile composite, and PA1 (3) adding dopant to the composite.

BACKGROUND OF THE INVENTION 
The present invention is directed generally to electrically conductive 
composites containing polyacetylene and high nitrile polymers. The 
invention relates to the preparation of electrically conductive composites 
such as polyacetylene in a high nitrile polymer matrix that can optionally 
contain mono-ethylenically-unsaturated comonomers, conjugated diolefins or 
mixtures thereof. In another aspect, the invention relates to novel 
electrically conductive composites, which composites are environmentally 
stable, exhibit solvent resistance and have good uniformity of dispersion. 
Conductive polymer are highly sought after at the present time to serve as 
substitutes for metals in a variety of applications conducting 
electricity. Many varieties of electronically conductive polymers are 
known in the art. These compositions have varied in their polymer 
structure and have included conductive components of polyacetylene, 
polypyrrole, poly-p-phenylene and poly-p-phenylene sulfide. Polyacetylene 
is a material of considerable interest because it can be rendered highly 
conductive by treatment with a variety of electron donors or acceptors. 
However, these organic polymer compositions lose stability under ambient 
conditions, rapidly lose their conductivity when exposed to ambient 
atmosphere, have poor mechanical properties and poor processability. There 
exists a need for develop conducting polymers with improved properties. 
A current approach as found in M. E. Galvin and G. E. Wnek, J. Polymer 
Sci., Polymer Chemistry Ed. 21, 2727 (1983), and U.S. Pat. No. 4,394,304 
involves the in situ polymerization of acetylene in polymer films of 
low-density polyethylene, impregnated with a catalyst. These composites 
have good mechanical properties and conductivities. These composites, 
however, suffer from inadequate air stability in that the conductivity 
dramatically decreases over a short period of time upon exposure to air. 
Furthr, these composites suffer from poor uniformity. 
It is an object of this invention to provide electrically conductive 
composites comprising polyacetylene and high nitrile resin. It is another 
object of this invention to provide electrically conductive composites 
that are environmentally stable when exposed to ambient atmosphere. It is 
another object of this invention to distribute the polyacetylene uniformly 
throughout the electrically conductive composites. It is another object of 
this invention to provide lightweight and inexpensive devices for 
electromagnetic interference shielding. 
These and other objects, together with the advantages over known methods, 
shall become apparent from the specification which follows and are 
accomplished by the invention as hereinafter described and claimed. 
SUMMARY OF THE INVENTION 
It has now been found that electrically conductive composites of 
polyacetylene can be prepared in the presence of high nitrile resins as a 
means of protecting the conductive polymer from the deleterious effects of 
the ambient atmosphere. The use of high nitrile resins provide greater 
protection to the conductive polymer since nitrile resins are excellent 
barriers to deleterious components of the atmosphere. The present 
invention further provides that the high nitrile resins also function as a 
component of the polymerization catalyst system so that there is uniform 
distribution of the polyacetylene in the composite. 
This invention relates to an electrically conductive composite comprising a 
conductive polyacetylene moiety, a nonconductive high nitrile resin, the 
high nitrile resin further comprising at least nitrile polymers or 
copolymers, and a dopant. Optionally the high nitrile resin comprises 
comonomers selected from the group consisting of unsaturated 
mono-ethylenically unsaturated monomers, conjugated diolefins and mixtures 
thereof and further optionally an elastomeric component. 
The invention further includes a process for producing an electrically 
conductive composite comprising: 
(1) impregnating a high nitrile resin with a Zeigler type catalyst 
comprising an alkyl aluminum compound and a material selected from the 
group consisting of alkyl, alkyl halide, alkoxide or oxyhalide of Group 
IVA and VA metals, 
(2) exposing the impregnated high nitrile resin to acetylene under 
polymerization conditions whereby polymerization occurs to form a 
polyacetylene/nitrile composite, and 
(3) adding dopant to the composite. 
Conductive polymer are presently in demand to serve as substitutes for 
metals in a variety of applications conducting electricity. The 
electrically conductive composites of this invention can be used as 
shielding against electromagnetic interference. The electrically 
conductive composite of this invention can be used as a means for reducing 
or eliminating electromagnetic emissions as well as electromagnetic pickup 
by enclosing the device of concern in conductive materials of the present 
invention. Further, the composites of this invention are useful as 
electrostatic shielding of electric power cable and other articles. 
Furthermore, the composites of the instant invention are useful as tapes, 
shielding layers and other types of articles.

DETAILED DESCRIPTION OF THE INVENTION 
The electrically conductive composites of the instant invention are the 
products of the polymerization of conductive organic polymer precursors in 
the presence of a high nitrile resin. 
Conductive organic polymers that can be used in the practice of this 
invention may be any of those which can be prepared by polymerization in 
the presence of the matrix high nitrile polymer. Further, conductive 
organic polymer precursors that can be used in the practice of this 
invention include alkynes, non-conjugated diynes and the like. The 
conductive organic polymer precursors useful in this invention can be 
prepared by any method known in the art. Alkynes are characterized as 
acetylenic hydrocarbons which are a class of unsaturated hydrocarbons 
having the generic formula C.sub.n H.sub.2n-2 and a structural formula 
containing a carbon to carbon triple bond. Un-conjugated diynes are 
characterized as alpha, omega-alkyl diynes, composed of chains of 
methylene groups with acetylenic units at each end of the chain. These 
conductive organic polymer precursors can be employed alone or in 
combinations. 
The electrically conductive composites generally contain the conductive 
organic polymer from about 2 percent to about 75 percent, preferably from 
about 3 percent to about 50 percent and most preferably from about 4 
percent to about 25 percent of the total weight without dopant. 
The alkynes and their derivatives and homologues useful in forming 
conductive organic polymers include but are not limited to acetylene, 
methylacetylene, trifluoromethylacetylene, cyclohexyl acetylene, 
cyanoacetylene and the like. Most preferred is acetylene. 
The un-conjugated diynes and their derivatives and homologues useful in 
forming conductive organic polymers include but are not limited to 
1,6-heptadiyne, 1,5-hexadiyne and the like. Most preferred is 
1,6-heptadiyne. 
The second component of the electrically conductive composites of the 
present invention are high nitrile resins. The high nitrile resin matrix 
suitable for use in the instant invention are nitrile polymers and 
copolymers. The high nitrile resins useful in this invention can be 
prepared by any method known in the art. Representative examples of 
nitrile resins and their preparation include those disclosed in U.S. Pat. 
Nos. 4,379,875 and 4,374,948. The nitrile monomers can be employed alone 
or in combinations. 
The electrically conductive composites generally contain high nitrile resin 
from about 25 percent to about 98 percent, preferably from about 50 
percent to about 95 percent, and most preferably from about 75 percent to 
about 94 percent of the total weight without dopant. When monomers or 
copolymers of nitrile monomers are employed in the matrix with comonomers 
of monoethylenically unsaturated monomers, conjugated diolefins or 
mixtures thereof, then the composites contain from about 50 to about 5 
weight percent, preferably from about 30 to about 15 weight percent 
comonomers of the total weight without dopant. 
The nitrile monomers and their derivatives and homologues useful as 
monomers, homopolymers or copolymers in forming the high nitrile resins 
include but are not limited to acrylonitrile, methacrylonitrile, 
1,1-dicyanoethylene, tetracyanoethylene, itaconic acid nitrile, crotonic 
acid nitrile, alpha methylene glutaronitrile and the like. The most 
preferred are acrylonitrile and methacrylonitrile. 
The monomers suitable for use as comonomers with the high nitrile resins 
are selected from the group consisting of monoethylenically unsaturated 
comonomers, conjugated diolefin comonomers and mixtures thereof. The 
unsaturated monoethylene comonomers and conjugated diolefin comonomers can 
be prepared by any method known in the art. The unsaturated monoethylene 
and conjugated diolefin comonomers can be employed alone or in 
combination. 
The monoethylenically-unsaturated comonomer component copolymerizable with 
the high nitrile resins includes acrylates, vinyl aromatics, 
mono-alpha-olefins, cyclic olefins, vinylesters of carboxylic acids, vinyl 
halides, vinylidene halides and the like. 
The acrylates and their derivatives and homologues include but are not 
limited to methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl 
acrylate, lauryl methacrylate, cyclohexyl acrylate and the like. The most 
preferred are methyl acrylate, methyl methacrylate and ethyl acrylate. 
The vinyl aromatics and their derivatives and homologues include but are 
not limited to styrene, alpha-methylstyrene, para-t-butyl styrene, 
para-methyl styrene and the like. The most preferred are styrene and 
alpha-methylstyrene. 
The mono-alpha-olefins and their derivatives and homologues include but are 
not limited to ethylene, propylene, 1-butene, 1-hexene, i-butylene and the 
like. The most preferred are ethylene, propylene and i-butylene. 
The cyclic olefins and their derivatives and homologues include but are not 
limited to norbornene, indene, 5-methylene 2-norbornene, 
5-ethylidene-2-norbornene, dicyclopentadiene and the like. The most 
preferred are norbornene, indene, and 5-ethylidene-2-norbornene. 
The vinylesters of carboxylic acids and their derivatives and homologues 
include but are not limited to vinyl acetate, vinyl stearate and the like. 
The most preferred is vinyl acetate. 
The vinyl halides and their derivatives and homologues include but are not 
limited to vinyl chloride, vinyl fluoride, vinyl bromide and the like. The 
most preferred is vinyl chloride. 
The vinylidene halides and their derivatives and homologues include but are 
not limited to vinylidene chloride, vinylidene fluoride and the like. The 
most preferred is vinylidene chloride. 
Other exemplary monoethylenically-unsaturated comonomers include but are 
not limited to maleic anhydride, diethyl maleate, dibutyl maleate and 
diethyl fumarate. 
The conjugated diolefin comonomer component copolymerizable with the high 
nitrile resins include but are not limited to 1,3-butadiene; 2-methyl 
1,3-butadiene; 2,3-dimethyl-1,3-butadiene; 2-chloro 1,3-butadiene; 
1,3-pentadiene, 3 methyl 1,3-pentadiene; 4 methyl 1,3-pentadiene; 
1,3-hexadiene and the like. The most preferred are 1,3-butadiene; 2-methyl 
1,3-butadiene; and 2,3-dimethyl 1,3-butadiene. 
Various elastomeric materials are likewise suitable for admixture in the 
present invention as an additive to the resin. Typical elastomeric 
materials suitable for the present invention include but are not limited 
to conjugated diolefin copolymers, conjugated diolefin homopolymers, 
ethylene-propylene-diene terpolymers, and the like. 
The conjugated diolefin copolymers and their derivatives and homologues 
include but are not limited to butadiene-acrylonitrile copolymer, 
styrene-butadiene copolymer, styrene-isoprene copolymer and the like. The 
most preferred are butadiene-acrylonitrile copolymer and styrene-butadiene 
copolymer. 
The conjugated diolefin homopolymers and their derivatives and homologues 
include but are not limited to polybutadiene, polyisoprene, 
poly(2-chloro-1,3-butadiene), poly(2,3-dimethyl-1,3-butadiene) and the 
like. The most preferred are polybutadiene and polyisoprene. 
The ethylene-propylene-diene terpolymers and their derivatives and 
homologues include but are not limited to 
ethylene-propylene-(5-ethylidene-2-norbornene), ethylene-propylene-1, 
4-hexadiene and the like. 
It will be readily apparent to those skilled in the art that composites of 
the instant invention may be further modified by the addition of 
plasticizers, stabilizers, pigments, dispersants, extenders, fillers, 
reinforcing agents and other film formers. The composites of the instant 
invention may also optionally contain various UV light absorbers, 
antioxidant agents and dyes. All these additives and the use thereof are 
well known in the art and do not require extensive discussion, it being 
understood that any compound possessing the ability to function in such as 
manner, i.e., as a plasticizer, antioxidants agent, UV light absorber and 
the like, can be used so long as they do not deleteriously affect the 
electrically conductive composite and do not adversely affect the 
characteristics of the composite. 
The electrically conductive composites of the present invention are 
prepared by in situ polymerization. The high nitrile resin matrix is 
immersed in a hydrocarbon solution of the catalyst components to form a 
Zeigler type catalyst complex. The catalyst component comprises an alkyl 
aluminum compound and alkyl, alkylhalide, alkoxide, or oxyhalide of Group 
IVA and VA metals of the Periodic Table of Elements as found in the 61st 
edition of the Handbook of Chemistry and Physics. The ratio of Zeigler 
type catalyst complex used to the high nitrile resin is as high as about 
1.5 to about 1 and as low as about 0.06 to about 1. Further, the ratio of 
the alkyl aluminum compound to the alkyl, alkylhalide, alkoxide, or 
oxyhalide of Group IVA and VA metals is about 1 to about 5 to about 5 to 
about 1. It is preferable to mix the high nitrile resin with an alkyl 
aluminum compound to form a co-catalyst complex which is then exposed to 
alkyl, alkylhalide, alkoxides of Group IVA and VA or oxyhalide. 
Alkyl aluminum compounds include but are not limited to triethylaluminum, 
trimethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, 
diethylaluminum chloride, ethyl aluminum sesquichloride, 
diisobutylaluminum hydride, 1-phenyl-2-(diethylalumino)-1-heptene and the 
like. The most preferred is triethylaluminum. 
Alkyl, alkylhalide, alkoxide, or oxyhalide of Group IVA and VA metals 
include but are not limited to tetra(isobutyl)titanate, 
tetra(n-butyl)titanate, tetra(isopropyl)titanate, 
dicyclopentadienyltitanium dichloride, dicyclopentadienylzirconimum 
dimethyl, vanadium triacetylacetonate, vanadium oxytrichloride and the 
like. The most preferred is tetra(isobutyl)titanate. 
The high nitrile resin matrix is immersed in a hydrocarbon solution of 
catalyst components under an inert substantially oxygen free atmosphere 
and can optionally be heated from about 30.degree. C. to about 90.degree. 
C. The high nitrile resin Zeigler type catalyst complex may be heated for 
about 0.5 hours to about 18 hours. The high nitrile resin Zeigler type 
catalyst complex is then exposed to the organic polymer precursor allowing 
the polymerization reaction to occur forming the composite. The 
polymerization occurs at a temperature from about -78.degree. C. to about 
+95.degree. C., preferably from about -40.degree. C. to about +25.degree. 
C. Further the polymerization occurs at a pressure from about 1 psig to 
about 25 psig, preferably about 5 psig to about 15 psig. Polymerization 
can be carried out for about one minute to about three hours, preferably 
for about five minutes to about one hour. 
The composite is then doped to introduce electron donors or electron 
acceptors to the composite to obtain the desired electrical properties. 
Doping is performed by exposing the composite to the doping agent, vapor 
or immersing the composite in a solution of the doping agent at ambient 
temperature of about 15.degree. C. to about 30.degree. C. The doping time 
is dependent upon the physical characteristics of the composite and the 
chemical properties of the dopant. However, doping exposure time is 
generally from about 18 hours to about 1000 hours. Doping agents and the 
procedure thereof are generally well known in the art. Examples of 
suitable n-type doping agents include but are not limited to iodine, 
sulfuric acid, perchloric acid, arsenic pentafluoride, antimony 
pentafluoride, molybdenum pentachloride, tungsten hexachloride and the 
like. Examples of suitable p-type dopants include but are not limited to 
potassium naphthalide, sodium naphthalide, lithium naphthalide and the 
like. Most preferred is iodine. 
Alternatively, laminates of the organic polymer with high nitrile resins 
can be prepared by pressing an organic polymer film between high nitrile 
resin films. These procedures are generally well known in the art. The 
organic polymer and the high nitrile resin of the instant invention are 
made separately into films by known methods in the art. The organic 
polymer film is doped by exposing the organic polymer film to the doping 
agent as above. The organic polymer film is then laminated between the 
high nitrile resin films. The organic polymer film and high nitrile resin 
films are pressed together by means of pressure and temperature. The 
temperatures is from about 180.degree. C. to about 260.degree. C. 
preferably from about 200.degree. C. to about 230.degree. C. The 
laminating pressure can vary from about 2000 psig to about 20,000 psig, 
preferably from about 5,000 psig to about 10,000 psig. 
The electrically conductive composites of the present invention are 
comprised of the reactive products of the high nitrile resins and the 
conductive organic polymers. It is theorized that in situ polymerization 
of the organic polymer and the high nitrile resin provides an effective 
means of incorporating or intertwining the conductive organic polymer with 
the high nitrile resin matrix, because the alkylaluminum reacts with the 
high nitrile resin to form an effective co-catalyst for Zeigler type 
catalyst in polymerization. Thus, the use of such co-catalyst with Zeigler 
type catalyst in the polymerization of organic molecules would effectively 
incorporate the organic molecules with the high nitrile resin matrix 
resulting in good uniformity. It is theorized that during the lamination 
process there is crosslinking and cyclization occurring between the high 
nitrile resins and the organic polymers of the different films. 
The use of a high nitrile resin improves the durability and environmental 
stability of the composites of the present invention due to the barrier 
properties of the high nitrile resins. The combination of conductive 
organic polymers and high nitrile resins into a composite results in good 
uniformity, conductivity and environmental stability. 
SPECIFIC EMBODIMENTS 
The following examples demonstrate the process and advantages of the 
present invention. 
Test Method 
The following electrically conductive composites 1, 2, and 3 were prepared 
by dissolving about 3.1 g of polyacrylonitrile powder in about 31.3 g of 
N,N dimethylformamide containing about 0.65 g of ethylenecarbonate to 
control the evaporation rate of the solvent at ambient temperatures. A 
film was cast of approximately 5.4.times.2.3.times.0.0037 cm (centimeters) 
on a glass microscope slide by adding the solution onto the slide and then 
allowing the solvent to evaporate by placing the slide on a warm hot 
plate. The film was further dried at about 50.degree. C. in a vacuum oven 
at less than about 50 mm of mercury for about 60 hours. The film was then 
transferred to a glove box with a dry argon atmosphere. Approximately 0.2 
ml to about 0.5 ml of tetra(isobutyl)titanate was applied to the film, 
followed by about 0.2 ml to about 0.6 ml of triethyl aluminum (25 weight 
percent in toluene). The film was rinsed with n-heptane and then aged for 
about fifteen minutes and transferred to a jar with an inlet and outlet 
tube. Acetylene was admitted to the jar at about 4 psig, at about 
20.degree. C. and for about 30 minutes. The resulting composite was washed 
with toluene. Then the composite was immersed in n-pentane saturated with 
iodine for about 24 hours. Then the pentane was evaporated off the 
composite. The conductivity was measured by the four probe technique and 
the results are reported in Table 1. 
Composite Compositions 
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Composition 
Percent 
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Example 1 Polyacrylonitrile 
.about.54 
Acetylene .about.18 
Iodine .about.28 
Example 2 Polyacrylonitrile 
69 
Acetylene 14 
Iodine 17 
Example 3 Polyacrylonitrile 
92 
Acetylene 3 
Iodine 5 
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In example 1 there was a failure of equipment; therefore the inventor has 
determined by his best effort the percent of the components in the 
composition by reviewing the method used to prepare the composition and 
the results obtained. 
A four-probe array is used in determining the conductivity. A direct 
current is passed through the specimen between the outer probes and the 
resistance is measured between the inner probes by using a GenRad Model 
1666 DC Resistance Bridge. The conductivity is calculated by a standard 
equation from the resistance measurement. 
The results of the conductivity test show that the environmentally stable 
electrically conductive composites of the present invention demonstrate 
good electrical conductivity. 
Although the invention has been described in detail through the preceeding 
examples, these examples are for the purpose of illustration only, and it 
is understood that variations and modifications can be made by one skilled 
in the art without departing from the spirit and the scope of the 
invention. 
TABLE 1 
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Conductivities of Polymer Composites 
Composition Thickness (cm) 
Conductivity (s/cm) 
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1 0.0037 1.75 
2 0.0042 6.7 .times. 10.sup.-4 
3 0.0042 &lt;5 .times. 10.sup.-5 
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