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Description  |
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BACKGROUND OF THE INVENTION
This invention relates to the production of conductive organic polymers.
More particularly, it relates to processable conductive organic polymers
and to a method for their production.
Considerable effort has been expended by researchers toward the production
of polymers which exhibit electrical conductivity. For example, in ORGANIC
COATINGS AND PLASTICS CHEMISTRY, Vol. 43, pp. 774-6, Preprints of Papers
Presented by the Division of Organic Coatings and Plastics Chemistry at
the American Chemical Society 180th National Meeting, San Francisco,
Calif., Aug. 24-29, 1980, there is reported by A. F. Diaz et al., in the
paper "Electrosynthesis and Study of Conducting Polymeric Films", the
electropolymerization of pyrrole, using a variety of electrolyte salts as
counteranions. In Offenlegungsschrift DE No. 3325892 Al (published Jan.
31, 1985), there is disclosed a method for the production of fine-grain
pyrrole polymers by the treatment of pyrrole with an oxygen-containing
oxidation agent in solution in the presence of a conducting salt. A
summary of various approaches to the creation of electrically conducting
polymers is reported, for example, by J. Frommer, in "Polymer Research
Frontier: How Insulators Become Conductors", Industrial Chemical News,
Vol. 4, No. 10, October 1983.
Polymeric materials which have been proposed as conductive polymers, for
the most part, are characterized by one or more undesirable properties,
including instability under ambient conditions, poor physical integrity
(notably brittleness) and poor processability (insolubility or
intractability) severely limiting the production or fabrication of
conductive polymeric articles by conventional production or processing
techniques.
While various applications for conductive polymers have been proposed, for
example, in the manufacture of solar cells and batteries and for EMI
shielding, the physical properties and/or processability of a conductive
polymeric material will dictate in part the suitability of such materials
to particular applications. In my copending application "Processable
Conductive Polymers", U.S. Ser. No. 595,667, filed Apr. 2, 1984, there is
disclosed and claimed a processable electrically conductive organic
material and a method for the production of such polymer. The conductive
organic polymer, exhibiting improved flexibility and processability,
including coatability from solvents, is prepared by the
electropolymerization of an electropolymerizable monomer in the presence
of a dispersed phase of polymeric electrolyte having anionic surface
character (e.g., a polymeric latex having anionic surface character).
While the conductive polymer material can be processed by convenient
coating methods into electrically conductive films, it will be appreciated
that it would be advantageous to prepare processable electrically
conductive polymers by a method which is not dependent upon the
manufacturing and equipment limitations associated, in general, with
electrochemical methods.
SUMMARY OF THE INVENTION
It has been found that a processable electrically conductive organic
polymeric material can be provided by polymerizing an oxidatively
polymerizable monomer in a reaction medium containing an oxidizing agent
for the oxidative polymerization and a dispersed phase of polymeric
counterion having anionic surface character. The utilization of an
oxidizing agent to effect the oxidative polymerization, and employment of
a polymeric counterion in affiliation with the cationic charges of the
oxidatively polymerized monomer, permits the production of an electrically
conductive polymeric material that exhibits stability, good physical
integrity and which can be processed by conventional coating techniques.
In its method aspect, there is provided a method for the production of a
processable electrically conductlve organic polymer as aforedescribed,
which method comprises oxidatively polymerizing, in a polymerization
reaction medium, a monomer oxidatively polymerizable to a cationic
polymer, said reaction medium comprising a reaction mediumsoluble chemical
oxidizing agent for the oxidative polymerization and, in a dispersed phase
in the reaction medium during the oxidative polymerization and as a
counteranion for said cationic polymer, a polymer having anionic surface
character.
For a fuller understanding of the present invention, reference should be
made to the following detailed description.
DETAILED DESCRIPTION
The oxidative polymerization reaction employed in the production of the
conductive polymers of the invention can be performed on a variety of
oxidatively polymerizable monomeric compounds. Useful monomers are those
which can be oxidatively polymerized, in the presence of a suitable
counteranion material, to a polymer having a cationic character, either as
a partial or full charge. In general, the oxidatively polymerizable
monomer will exhibit solubility in the reaction medium (solvent) and will
be soluble at least to the extent of 10.sup.-5 Molar. Preferably, the
polymerizable monomer will be dissolved in the reaction medium at a
concentration of from 10.sup.-2 to 10.sup.-1 Molar, although the
concentration utilized will depend upon the particular nature of the
polymerizable compound and reaction solvent employed and the desired rate
of polymerization.
Suitable oxidatively polymerizable monomers useful in the method of the
present invention are aromatic heterocyclic compounds. Examples include
pyrrole; N-substituted pyrroles; .beta.-substituted pyrroles; thiophene;
.beta.-substituted thiophenes; furan; .beta.-substituted furans; indole;
and carbazole. If desired, aniline salts, e.g., aniline hydrochloride, can
be employed to provide a conductive polyaniline. Other monomers
oxidatively polymerizable to a polymer having a cationic character can,
however, be employed. The polymerizable monomer can be polymerized to a
homopolymer or can be copolymerized with one or more oxidatively
polymerizable monomers to provide an electrically conductive copolymer, if
desired.
The oxidatively polymerizable monomer useful in the production of polymers
of this invention can be substituted with one or more substituent groups.
In the case of a five-membered heterocyclic compound, the
.alpha.,.alpha.'-positions will be unsubstituted so as to permit
.alpha.,.alpha.'-coupling of monomeric units in a polymer chain. It will
be appreciated that the presence of substituent groups will influence the
rate of oxidation (polymerization) or the properties of the resulting
polymer. Suitable substituent groups include alkyl, aryl, aralkyl,
alkaryl, hydroxy, methoxy, chloro, bromo and nitro substituents. Suitable
substituent groups can be selected consistent with the desired
polymerizaticn conditions and the properties desired in the resulting
conductive polymer.
A class of aromatic heterocyclic compounds suited to the production of
conductive polymers by the method of the invention includes the
five-membered heterocyclic compounds having the formula
##STR1##
wherein each of R.sup.1 R.sup.2 independently hydrogen; alkyl (e.g.,
methyl or ethyl); aryl (e.g., phenyl); alkaryl (e.g. tolyl); or aralkyl
(e.g., benzyl); or R.sup.1 and R.sup.2 together comprise the atoms
necessary to complete a cyclic (e.g. benzo) structure; and X is
##STR2##
where R.sup.3 is hydrogen, alkyl, aryl, alkaryl or aralkyl. These
compounds provide in the resulting oxidatively polymerized material,
repeating units of the formula
##STR3##
wherein R.sup.1, R.sup.2 have the definitions set forth hereinbefore.
Preferred monomers include pyrrole and the substituted pyrroles such as
.beta.-.beta.'-dimethylpyrrole and .beta.-.beta.'-diphenylpyrrole. The
polymerizable monomer of choice is pyrrole which polymerizes readily and
which in affiliation with a polyanionic counterion permits the facile
production of an electrically conductive polymeric material characterized
by stability and processability.
The oxidative polymerization is effected in a suitable polymerization
reaction medium with the aid of an oxidizing agent. The polymerization
medium will comprise suitable solvent material for the oxidatively
polymerizable monomer. Typically water will be employed as a reaction
medium, although mixtures of water and organic solvent materials,
preferably water-miscible, can also be employed. The polymerization
reaction medium will include the oxidatively polymerizable monomer (and
copolymerizable monomers, if any), the oxidizing agent and the polymeric
counteranion material. The nature of the reaction medium (solvent) can
vary depending upon the particular nature of the polymerizable monomer(s),
oxidizing agent and polymeric counterion material employed. The solvent
should, however, be compatible with the reactants. Where, for example, an
aqueous solvent mixture is employed, care should be exercized that the
solvent not be incompatible with the maintenance of the polymeric
counteranion material in a dispersed condition in the reaction medium. In
the case of pyrrole, a preferred oxidatively polymerizable monomer, water
can be conveniently employed as the polymerization medium for the
production of stable conductive polymers having improved processability.
The oxidizing agent used to effect the oxidative polymerization can include
any of a variety of known oxidizing agents. Suitable oxidizing agents
include those which are soluble in the polymerization reaction medium and
which suitably oxidize the polymerizable monomer to a polymer having a
cationic character. As used herein, a "cationic polymer" or a "polymer
having a cationic character" refers to a polymer (of oxidatively
polymerized monomer) wherein there is present a positive charge
distributed among one or more of the repeating monomer units. Peroxygen
compounds can be used, including the common inorganic peroxy-compounds
such as the alkali metal and ammonium perborates, percarbonates,
perchromates, monopersulfates, and monoperphosphates. Examples include
sodium perborate; potassium perborate; ammonium perborate; sodium
percarbonate; potassium percarbonate; potassium bichromate; alkali metal
or ammonium persulfates such as potassium monopersulfate; complex
per-salts such as MHSO.sub.4.M.sub.2 SO.sub.4.2MHSO.sub.3, where M is
potassium or sodium; potassium persulfate, K.sub.2 S.sub.2 O.sub.8 ;
sodium percarbonate, potassium percarbonate; and sodium monoperphosphate.
Other oxidizing agents can, however, be used such as nitrous acid;
perchloric acid; hydrogen peroxide; ferric chloride; diazonium salts; lead
dioxide; ozone; potassium permanganate and the water-soluble organic
peroxy acids of the formula
##STR4##
wherein R is a substituted alkylene or arylene group and Z
##STR5##
or any other group which yields an anionic group in aqueous solution, and
the alkali metal salts thereof. Examples of organic peroxy-compounds are
the aliphatic and aromatic percarboxylic acids and their alkali metal and
ammonium salts. Among the aliphatic peracids may be mentioned peracetic
acid, perpropionic acid, perlauric acid and the like. Aromatic peracids
include perbenzoic acid and nuclear-substituted perbenzoic acids such as
p-methoxyperbenzoic acids.
The amount of oxidizing agent utilized for the production of the conductive
polymers can vary with the nature of the polymerizable monomer (or mixture
of copolymerizable monomers) and with the particular oxidizing agent
employed. In general, however, the molar proportion of oxidizing agent to
polymerizable monomer will be in the range of from 0.005:1 to 0.5:1. The
use of a proportion of about 0.005:1 or higher promotes adequate
conversion of monomer to desired polymers. A proportion greater than about
0.5:1 tends to be non-economic and may promote the production of coagulum
in the polymerization medium. If desired, the coagulum can be redispersed
in a suitable vehicle, usually organic, for production of a coatable
composition useful in the production of electrically conductive films. A
preferred ratio of oxidizing agent to polymerizable monomer is from about
0.009:1 to about 0.03:1.
The dispersed phase of anionic polymer in the polymerization medium during
the polymerization reaction provides the electrical neutrality for the
cationic polymer Produced by the oxidative polymerization and serves an
important function in conferring processability to the resulting
conductive polymer. In the production of a conductive polymer of the
invention, from an oxidatively polymerizable monomer such as pyrrole,
thiophene or the like, the polymer having anionic surface character will
comprise an integral portion of the resulting organic conducting polymer.
The stoichiometry of, for example, a conductive polymer of an aromatic
heterocyclic compound, can be appreciated by reference to the following
formula (I) for polypyrrole (Mol. Cryst. Liq. Cryst., 1982, Vol. 83, pp.
253-264):
##STR6##
wherein A .crclbar. represents the electrochemically stoichiometric anion
and n is an integer. It will be seen from inspection of formula (I) that
the relative weight of the counteranion A .crclbar. in relation to the
cationic portion will depend upon its size.
According to the present invention, the anionic portion of the conducting
polymer will comprise a bulky counterion as a consequence of employing, as
a counterion material during the oxidative polymerization, a polymer
having anionic surface character. The polymeric counteranion comprises a
major proportion by weight of the conductive polymer and markedly enhances
physical properties and processability. When the counterion is, for
example, a sulfonate or sulfate group on the surface of a latex particle,
it will have a major influence on the final weight percent of each of the
cationic and anionic portions. In general, the polymeric counterion will
comprise from about 50% to about 97% by weight of the conductive polymer.
Correspondingly, repeating units from the oxidatively polymerizable
monomer will comprise from about 3% to about 50% by weight.
The nature of the polymer utilized as the counterion material can vary with
the nature of the physical properties desired in the resulting conductive
polymer. Inasmuch as the nature of the counteranion as a bulky moiety in
relation to the cationic moiety will cause the counteranion to constitute
a relatively large percentage (by weight) of the resulting polymer, it
will be appreciated that considerable latitude will be afforded in
tailoring the physical properties of a conductive polymer to the
predetermined requirements of a particular application by suitable choice
of the polyanionic polymeric counterion.
The polymeric counterion mterial is employed in the polymerization medium
in a dispersed phase. As used herein, a dispersed phase refers to a stable
dispersion or emulsion of polymer in the liquid or solvent used to conduct
the polymerization of the oxidatively polymerizable monomer. The liquid
can, and preferably will, be water although other solvent materials, as
pointed out hereinbefore, can be used as the solvent for the polymerizable
monomer. The polyanionic polymer used as the counterion material must,
however, be present during the polymerization as a dispersed phase so as
to assure the availability and affiliation of the cationic charges (of the
oxidatively polymerized material) with the anionic surface charges of the
dispersed counterion polymer, as required for the production of
electrically conductive species.
A dispersed phase of polymer having anionic surface character can be
conveniently provided by preparing an emulsion polymer or latex according
to conventional emulsion polymerization techniques. The preparation of
latices is ordinarily accomplished by polymerizing an ethylenically
unsaturated monomer (or mixture of copolymerizable ethylenically
unsaturated comonomers) in a suitable solvent such as water, a
water-soluble hydroxylated organic solvent such as alcohol, polyhydroxy
alcohol, keto alcohol, ether alcohol or the like, or in a mixture of water
and such a hydroxylated solvent, such a mixture usually containing a major
amount of water. The preparation of a latex will normally be accomplished
by polymerization of an ethylenically unsaturated monomer (or mixture of
comonomers) in the presence of a surfactant, dispersing agent, emulsifier
or protective colloid, the material being present in sufficient quantity
to cause formation of a stable emulsion. Suitable surfactants, emulsifiers
and colloid materials used in the production of latices include cationic
materials such as stearyl dimethyl benzyl ammonium chloride; nonionic
materials such as alkyl aryl polyether alcohols and sorbitan monooleate;
anionic materials such as sodium dodecylbenzene sulfonate, dioctyl sodium
sulfosuccinate, sodium salts of alkyl aryl polyether sulfates and sodium
alkyl (e.g., lauryl) sulfates; alkali metal salts of lignosulfonic acids,
and silicic acids; and colloidal materials such as casein, sodium
polyacrylate, carboxymethylcellulose, hydroxyethylcellulose, gelatin,
sodium alginate or polyvinyl alcohol. The particular surfactant or like
material employed can be varied depending upon the desired properties of
the latex polymer and the nature of the polymerizable monomers thereof.
The negatively charged (polyanionic) surface character of the dispersed
phase of counterion polymer can be incorporated in various ways. For
example, an ethylenically unsaturated polymerizable monomer having a
strong ionic group, e.g., a sulfate or sulfonate group, can be used as a
polymerizable monomer in the production of the polymeric supporting
electrolyte. Thus, a copolymerizable surfactant including a polymerizable
ethylenically unsaturated moiety and a sulfate or sulfonate group can be
polymerized by emulsion polymerization technique with an ethylenically
unsaturated monomer or mixture thereof to provide a polymer latex having
the anionic surface character of the sulfate or sulfonate moiety. A
suitable copolymerizable monomer for this purpose is a copolymerizable
short-chain vinyl sulfonate such as the sodium salt of allyl ether
sulfonate (available as COPS I, Alcolac, Inc.) having the formula:
##STR7##
Other polymerizable monomers having an anionic group include 2-sulfoethyl
methacrylate; 2-acrylamido-2-methylpropanesulfonic acid; vinylbenzene
sulfonic acid; sodium vinyl sulfonate; or the salts of any of the
aforementioned acids. Other polymerizable monomers capable of introducing
anicnic character to a dispersed phase of polymer can, however, be
suitably employed.
The polyanionic surface character of the dispersed polymeric counterion
material can also be the result of the utilization of an anionic
surfactant (having a strong ionic character) in connection with the
manufacture of the polymer by emulsion polymerization technique. Thus, a
surfactant or emulsifier having, for example, a sulfate or sulfonate
moiety can be employed as the surfactant or emulsifier according to known
emulsion polymerization technique for the production of a latex having the
anionic surface character of the anionic moiety. Any of the anionic
surfactants or emulsifiers mentioned hereinbefore can be used for this
purpose. It will be preferred, however, to incorporate polyanionic surface
character by using a copolymerizable surfactant compound as hereinbefore
described.
As mentioned previously, the physical properties of the conductive polymers
of the invention will be influenced materially by the nature of the
polyanionic counterion polymer and, accordingly, the comonomers utilized
in the production of polyanionic polymers can be selected so as to
introduce predetermined properties suited to a particular application.
Thus, a variety of ethylenically unsaturated compounds can be employed to
produce a polymeric counterion material, provided that surface anionic
character is introduced into the polymer and provided that the counterion
polymer be capable of being in a dispersed state in the medium in which
the oxidative polymerization monomer is performed. Examples of such
monomers include the esters of unsaturated alcohols such as vinyl alcohol
and allyl alcohol with saturated acids such as acetic, propionic or
stearlc acids, or with unsaturated acids such as acrylic or methacrylic
acids; the esters of saturated alcohols with unsaturated acids such as
acrylic and methacrylic acids; vinyl cyclic compounds such as styrene;
unsaturated ethers such as methyl vinyl ether, diallyl ether and the like;
the unsaturated ketones such as methyl vinyl ketone; unsaturated amides
such as acrylamide, methacrylamide and unsaturated N-substituted amides
such as N-methyl acrylamide and N-(1,1-dimethyl-3-oxobutyl) acrylamide;
unsaturated aliphatic hydrocarbons such as ethylene, propylene and the
butenes including butadiene; vinyl halides such as vinyl chloride, vinyl
fluoride and vinylidene chloride; esters of unsaturated polyhydric
alcohols such as esters of butenediol with saturated or unsaturated acids;
unsaturated acids such as acrylic acid, methacrylic acid, maleic, fumaric,
citraconic or itaconic acids (or the halides or anhydrides thereof); and
unsaturated nitriles such as acrylonitrile or methacrylonitrile. Other
polymerizable monomers can be employed to introduce desired properties
such as hydrophobicity, hydrophilicity or the like and can contain
particular moieties such as silicone, fluoro, oxirane, oximino or other
groups to provide properties suited to particular applications.
Preferably the counterion polymer will be prepared by emulsion
polymerization and will be in the form of a latex. Utilization of a
dispersed polymer, e.g., a polymeric latex that can be conveniently coated
into a polymer film, contributes importantly to the production by
conventional coating methods of electrically conductive polymeric films.
Known emulsion polymerization techniques as described hereinbefore can be
used to prepare suitable polymeric latex counterion materials. Free
radical catalysts such as the peroxides, alkali metal or ammonium
persulfates, azobisisobutyronitrile or the like can be used for the
provision of such latices. The size of dispersed, e.g., latex, particles
and the surface charge density can be varied substantially by resort to
variations in the nature of the monomers employed and the conditions of
polymerization, as is known by those skilled in the art. In general,
polymer particles having an average particle size diameter of 50 to 500
nanometers provide good results. Other particle sizes can, however, be
utilized.
A polyanionic polymer can be prepared by other techniques and can then be
provided in a liquid medium as a dispersed phase. For example, a
solution-polymerized polymer can be dispersed in a non-solvent material.
Care should be exercised, however, in the production of a dispersion to
avoid conditions promoting appreciable solubilization of the polymer in
the desired dispersing medium.
The conductive polymer of the invention can be conveniently prepared by
introducing the polymerizable monomer (or mixture of copolymerizable
monomers) into a reaction medium containing the dispersed polymeric
counterion material (e.g., a polymeric latex), followed by addition of the
oxidizing agent. The reaction (polymerization) can be suitably performed
under ambient conditions and the conductive polymer material can be
filtered for recovery of the desired material as a coatable dispersion or
latex. Other addition sequences can, however, be employed.
The conductive polymer material prepared by the method hereof can be coated
onto a variety of substrate materials to provide a conducting layer or
film of polymer. It will be appreciated that depending upon the particular
application fo the conductive polymer film or layer, the nature of the
polymeric counterion material can be varied so as to tailor the properties
of the resulting conductive polymer material to the requirements of the
particular application. Various adjuvants can be incorporated into the
conductive polymers of the invention to provide particular and desired
functionality. For example, cross-linking agents, organic surfactants,
dyes or the like can be used. Such agents can be incorporated into the
polymeric counterion material during the production thereof or can be
introduced into the reaction medium in which the oxidative polymerization
of the invention is performed or can be incorporated into the finished
conductive polymer material, provided that such incorporations do not
interfere or otherwise negate the desired production of an electrically
conductive and processable polymeric material.
While the applicant does not wish to be bound by any particular theory or
mechanism in explanation of the manner in which processable and conductive
polymers are produced by the practice of this invention, it is believed
that the production of conductive species is importantly related to the
electrical affiliation promoted by the availability of the anionic charges
on the surface of dispersed particles to cationic charges generated by the
oxidative polymerization of the polymerizable monomer(s). The conductive
polymer can be represented in the case of polypyrrole by the following:
##STR8##
wherein a is a value in the range of about two to about four, depending
upon the nature of the charge distribution of the particular counteranion
A .crclbar. present on the surface of the polyelectrolyte polymer and n is
an integer. It will be appreciated that the presence of a plurality of A
.crclbar. moieties on the surface of the polymer allows a number of such
moieties to be affiliated with the illustrated cation; and it will be
understood that not all anionic moieties A .crclbar. on the surface of the
polymer will be in affiliation with the illustrated cation.
The invention will be further decribed by reference to the following
Examples which are intended to be illustrative and non-limiting.
EXAMPLE 1
Part A--A polymeric latex having anionic surface character was prepared in
the following manner employing a reaction vessel fitted with a condenser,
mechanical stirrer, gas inlet (and outlet), thermometer, and dropping
funnel. Water (3408 ml.) and 90 grams of a solution of copolymerizable
surfactant (sodium salt of allyl ether sulfonate, 40% active, available
under the tradename COPS-I from Alcolac, Inc.) were added to the reaction
vessel with stirring. The contents of the vessel were purged with nitrogen
and heated to 80.degree. C. A pre-mix of the following monomers was
prepared: 427 mls. ethyl acrylate; 208 mls. methyl methacrylate and 7.4
mls. methacrylic acid. To the reaction vessel, 90 mls. of the monomer
pre-mix were added and the contents were heated, at 80.degree. C., for two
minutes. Potassium persulfate (90 gms.) was added and washed into the
vessel using several mls. of water, as required. A latex seed was allowed
to form by stirring at 80.degree. C. for 11 minutes. The nitrogen was
moved from below the surface of the liquid in the reaction vessel to the
space above the surface of the liquid and a nitrogen flow rate (2-4
cc./min.) was maintained throughout the reaction. The remaining quantity
of the monomer pre-mix was added dropwise at a rate such that the total
addition was accomplished over a period of one hour. Temperature was
maintained at 80.degree. C. After the monomer pre-mix was added, the
contents of the reaction vessel were heated at 80.degree. C. for 45
minutes. The reaction contents were cooled to room temperature under
nitrogen purge and the reaction product was filtered through cheesecloth.
The polymeric latex had a solids content of 10.7% by weight and was
utilized as a polymeric counterion material in the manner described in
Part B of this Example.
Part B--Into a flask containing 100 mls. of the polymeric latex (10.7%
solids) described in Part A of this Example, were added with stirring 3
mls. of pyrrole and 500 mgs. of potassium persulfate (K.sub.2 S.sub.2
O.sub.8) The reaction was allowed to run for 15 minutes. The resulting
latex polymer was cast into a film which was allowed to dry overnight in
air at room temperature. The film was electrically conductive (surface
resistance of about 30 megaohms/square).
Part C--The experiment described in Part B of this Example was repeated
except that there was employed 100 mls. of polymeric latex obtained by
diluting the starting polymeric latex (10.7% solids) 1:1 with water (to
5.35% solids). A film prepared as described in Part B of this Example
showed a surface resistance of about 30 megaohms/square.
EXAMPLE 2
Part A--A polymeric latex having anionic surface character was prepared in
the following manner employing a reaction vessel fitted with a condenser,
mechanical stirrer, gas inlet (and outlet), thermometer, and dropping
funnel. Water (2230 grams) and 228 grams of 40% active solution of sodium
salt of allyl ether sulfonate (COPS-I, Alcolac, Inc.) were added to the
reaction vessel and heated to 80.degree. C. while purging with nitrogen. A
pre-mix of the following monomers was prepared: 790 grams ethyl acrylate,
387.4 grams methyl methacrylate and 15 grams methacrylic acid. To the
reaction vessel, at 80.degree. C., were added 60 grams of the monomer
pre-mix. The contents were stirred for five minutes at 270 rpm. A solution
of 50 grams water and 40.5 grams (NH.sub.4).sub.2 S.sub.2 O.sub.8 was
added dropwise over a period of three minutes and twenty seconds. The
reaction vessel contents were stirred for five minutes and the remaining
portion of the monomer pre-mix was introduced dropwise over a period of 96
minutes. Seed polymer was observed to form within seconds of the first few
drops of initiator solution added. The seed polymer was blue and
translucent by the time the monomer addition began. When the monomer feed
was completed, the reaction product was heated for 60 minutes at
80.degree. C. The presence of some foam was observed during this time. The
product was cooled to 25.degree. C. and filtered through cheesecloth.
Filtration was slow by reason of the presence of fine coagulum in the
product. A latex (white in appearance and having a solids content of
34.5%) was obtained and employed in the experlment described in Part B of
this Example.
Part B--A quantity of the latex prepared as described in Part A of this
Example (21.87 grams) was introduced into a reaction vessel and diluted to
100 grams with water to provide a latex of 7.54% solids. To the resulting
latex were added three mls. of pyrrole. Potassium persulfate (500 mgs.)
was then added and the contents of the reaction vessel were stirred at
room temperature. A dispersion of conductive polypyrrole was prepared.
Films coated from the resulting dispersion onto glass showed surface
resistance in the megaohm/square range.
EXAMPLE 3
This Example illustrates the production of a conductive polymer material
from a commercially available synthetic anionic colloidal emulsion of
vinyl chloride copolymer in water (Geon.RTM. 450.times.61 Latex, The BF
Goodrich Company, Chemical Group, Cleveland, Ohio). Into a reaction vessel
were added about 25 grams of the aforementioned commercially available
latex (pH 5.0; 54% solids; 15 centipoise Brookfield Viscosity, Spindle No.
2, 60 rpm at 25.degree. C.; 1.110 specific gravity). The latex was diluted
to 100 grams with distilled water and three grams of pyrrole were added.
The contents of the vessel were stirred for one minute. To the mixture
were added 500 mgs. of potassium persulfate. The contents were allowed to
stir in air. After several minutes, the reaction mixture was observed to
darken. The contents were stirred for about seven additional minutes. Two
aliquots of reaction product were removed and each was coated onto a glass
slide. The slide prepared from the first aliquot was heated at about
100.degree. C. for 1.5 hours. A black film showing very slight optical
transmission was formed. Surface resistance was measured (54
kiloohms/square). The slide prepared from the second aliquot was allowed
to dry at room temperature for several hours. A black film showing
slightly greater optical transmission and having a surface resistance of
about 150 kiloohms/square was obtained.
EXAMPLE 4
Conductive polymer material was prepared in the manner described in Example
3 except that 10.43 grams of the Geon.RTM. 450.times.61 Latex were diluted
to 100 grams with water (to provide a solids content of about 5.6%). After
addition of three mls. of pyrrole, the contents were stirred for several
minutes and 500 mgs. of potassium persulfate added. The reaction contents
were stirred at room temperature. After about two minutes, the presence of
a small amount of coagulum was observed on the bottom of the reaction
flask. Aliquots were taken at two minutes, nine minutes and 30 minutes.
Glass slides prepared from these aliquots were dried in an oven at
100.degree. C. to provide slightly transmissive polymer films having
surface resistance in the 20-50 kiloohm/square range, depending upon
coated thickness.
EXAMPLE 5
A conductive polymer material was prepared in the manner described in
Example 3 except that 10.43 grams of the Geon.RTM. 450.times.61 Latex were
diluted to 99 grams with water, and after addition of three mls. of
pyrrole and stirring for three minutes, a solution of ammonium persulfate
(250 mgs. dissolved in one ml. of water) was added. The reaction contents
were stirred overnight. A first aliquot was taken ten minutes after the
persulfate addition and was coated onto a glass slide. The slide was dried
at room temperature overnight and exhibited surface resistance in the low
(7-10) kiloohm/square range. A second aliquot (taken after overnight
stirring) was coated onto a glass slide and dried at 100.degree. C. in an
oven. The resulting film had a surface resistance in the thickest areas of
the film of about five kiloohms/square.
EXAMPLE 6
This Example illustrates the production of a conductive and processable
polyaniline from aniline hydrochloride. Using the procedure described in
Example 3, ten grams
of the Geon.RTM. 450.times.61 Latex diluted with water to 100 grams and
three grams aniline hydrochloride and 250 mgs of ammonium persulfate were
reacted. The reaction contents were allowed to stir for about 15 minutes A
green dispersion resulted. A film was cast from the reaction product onto
a glass slide and was dried at 100.degree. C. The film was green and
showed the presence on the surface a quantity of white polymer material.
The film also showed discontinuities (holes) Surface resistance was about
2.5 megaohms/square.
EXAMPLE 7
The procedure decribed in Example 6 was repeated using three grams of
aniline in place of the aniline hydrochloride. The reaction mixture became
beige in color A transmissive tan-colored film prepared by coating a glass
slide and drying the film was found to have a surface resistance about 200
megaohms/square.
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