Electrically conductive pyrrole polymers

A process is provided for forming an electrically conductive polymer of a pyrrole monomer, optionally substituted at the 3- and 4- positions. The process comprises dispersing a polymerization initiator selected from the group consisting of anhydrous halides of iron, cobalt or nickel (Group VIII metal) in an anhydrous liquid reaction medium and, adding essentially pure pyrrole monomer, or a solution of the monomer in the liquid at a temperature in the range from about -20.degree. C. to below about the boiling point of the solution. The pyrrole polymer so formed is a Group VIII metal halide counterion, and a conductor having a conductivity in the range from about 1 to about 150 ohm.sup.-1 cm.sup.-1 ("S/cm" for brevity), or a semiconductor having a conductivity in the range from about 10.sup.-3 to about 1 S/cm, depending upon the particular structure of the monomer, the ratio of the initiator to pyrrole monomer, and the molecular weight of the polymer formed. Ratios greater than 4 generally yield conductors, while ratios in the range from about 0.25 to 4 yield semiconductors. Conductive polypyrrole having only a chloride or bromide counterion is formed in acetonitrile. The chemical process of this invention may be used to form the pyrrole polymer on a substrate such as paper by soaking it in liquid pyrrole, then dipping the pyrrole-impregnated paper into a solution of anhydrous ferric chloride in diethyl ether.

BACKGROUND OF THE INVENTION 
This invention relates to organic conductors and semiconductors which fall 
into the group of polymeric pyrrole conductors. As is well known, such 
conducting polymers defy conventional melt-processing, cannot be 
compacted, whether molded or extruded, in the usual ways, nor deposited as 
a continuous film from solution; and, they are far from stable in air even 
at ambient temperature conditions. A polymer which defies compaction into 
a shaped article, places severe limitations upon its use. Certain pyrrole 
polymers made by electrodeposition are found to be compactable (see 
copending U.S. patent application Ser. No. 486,161, filed Apr. 18, 1983), 
and to form self-supporting films, but this process is too slow for 
general commercial utility. The problem was to find a relatively fast 
non-electrochemical process which yielded a compactable conductor (the 
term "conductor" as used herein includes semiconductors) so that the 
polypyrroles formed might be more versatile in their applications. 
By "semiconductors" I refer to polymers of pyrrole/substituted pyrrole 
monomers which have relatively low conductivity in the range from about 
10.sup.-3 ohm.sup.-1 cm.sup.-1 ("S/cm" for convenience to indicate 
reciprocal ohms/cm) to 1 S/cm, while "conductors" have a conductivity in 
the relatively high range of from 1 to about 150 S/cm. 
Poly(2,5-pyrrole) (referred to herein as "PP" for brevity), in which the 
--NH-- group links sequences of conjugated double bonds, is normally an 
insulator, that is, has a conductivity less than about 10.sup.-10 S/cm and 
is totally insoluble in known solvents. It is known however, that 
electrochemically polymerized PP has good conductivity, but coupled with 
its melt-processing-resistance and the poor integrity of PP film so 
formed, it was deemed more desirable to produce the PP with a chemical 
process. Others have also sought to do so. In particular, German (FDR) 
Offenlegungasehrift DE 3321281 A1 published Dec. 22, 1983 discloses a 
chemical process for producing a conductive paper by impregnating the 
paper with different concentrations of an aqueous ferric chloride solution 
which is acidified with HCl, then exposing the impregnated paper to 
pyrrole monomer, usually in the gaseous phase. Further details of this 
process are disclosed in an article titled "Some Properties of 
Polypyrrole-Paper Composities" by Bjorklund, R. B. and Lundstroem, I., 
Journal of Electronic Materials, Vol 13, No. 1, 1984. 
As also stated in Bjorklund et al, they were aware that anhydrous 
FeCl.sub.3 used as a dopant with poly-p-phenylene exists as an FeCl.sub.4 
(2.sup.-) complex in the polymer matrix, thus imparting conductivity to 
the polymer. Other polymers, for example polyacetylene impregnated with 
FeCl.sub.3 or other oxidants such as SbCl.sub.5, and, neutral polypyrrole 
which is exposed to FeCl.sub.3 vapor or an anhydrous solution of the 
electrolyte, is also made conductive. But impregnating a preformed polymer 
with FeCl.sub.3 to make it conductive does not suggest that one may use 
anhydrous FeCl.sub.3 as an initiator to form the polymer from the pyrrole 
monomer, or that the FeCl.sub.3 would generate a charged species in the 
polymer formed. As is well-known, poly-p-phenylene cannot be formed by 
initiation with FeCl.sub.3 (see "Reaction of Ferric Chloride with 
Benzene", by P. Kovacic and C. Wu, J. Polym. Sci. Vol XLVII pg 45-54 at pg 
45, first sentence of "Results", 1960), and the polymer is not conductive 
unless post-treated with FeCl.sub.3. 
The insulating character of PP produced by Naarman is attributable to the 
combination of AlCl.sub.3 and Cu.sup.+2 Cl.sub.2 as the initiator, further 
possibly to the low molar ratio of the initiator to the pyrrole in the 
reaction mixture. 
With respect to polymers of 3- and/or 4- substituted pyrroles ("subs PP"), 
Bjorklund et al corroborate the generally well known fact that providing 
substituents on pyrrole does not improve the conductivity of the subs PP. 
Yet, with the process of my invention, the designated subs PP has 
relatively good conductivity. 
As noted by Bjorklund et al, their precipitated PP was compactable under 10 
ton pressure to form a wafer. PP precipitated in my polymerization 
reaction is compacted under far less pressure into a wafer which can be 
handled, but the wafer, unlike wafers or films produced from 
electrochemically produced PP, has essentially no tensile strength. 
The conductive PP/subs PP of the prior art which polymers owe their 
conductivity to exposure to an electrolyte of a Group VIII metal, for 
example FeCl.sub.3, whether by exposure to FeCl.sub.3 vapor, or by 
impregnation with an anhydrous solution of electrolyte, derive their 
conductivity from a FeCl(2.sup.-) counter ion in which the Fe (or other 
Group VIII metal) is always present. It was therefore surprising to find 
that excellent conductivity, as high as 150 S/cm, may be obtained with 
only Cl present as the counter ion, and without the presence of Fe. 
Though it appeared that the type of initiator (electrolyte) would affect 
the electrical properties of the polymer, the possibility that the solvent 
might affect the charged species in the polymer was given little 
consideration. And the possibility that a single initiator could provide 
different charged species in the same polymer if it is formed under 
different conditions, was given even less consideration. Thus the 
formation of PP/subs PP.sup.+ Cl.sup.-1 by a direct, single-step chemical 
process was both significant and unique. 
SUMMARY OF THE INVENTION 
I have discovered that pyrrole, optionally substituted with a wide variety 
of substituents in the 3- and/or 4- positions, may be polymerized in a 
chemical, but non-electrochemical reaction, to form a finely divided 
poly(2,5-pyrrole) which is conductive, is compactable but has essentially 
no tensile strength; and is therefore preferably applied to an insulating 
substrate to enhance its conductivity into the range from about 10.sup.-3 
to about 150 S/cm. 
It is therefore a general object of this invention to provide a process for 
forming an electrically conductive PP/subs PP polymer comprising, 
(a) dispersing a finely divided anhydrous polymerization initiator selected 
from the group consisting of halides of a Group VIII metal selected from 
iron, cobalt and nickel in an anhydrous organic liquid reaction medium 
with which said initiator is unreactive, so as to form a dispersion of 
said initiator in said medium, and, 
(b) adding anhydrous essentially pure liquid pyrrole monomer, optionally in 
solution in said medium, to said dispersion at a temperature in the range 
from above the freezing point of said medium to below its boiling point, 
so as to form said polymer which contains an ion selected from the group 
consisting of a Group VIII metal, halogen, and combinations thereof as 
charged species, said monomer having the structure 
##STR1## 
wherein, 
R.sup.1 is selected from the group consisting of hydrogen, alkyl having 
from 1 to about 6 carbon atoms, cycloalkyl having from 3 to about 7 ring 
carbon atoms one or more of which may be subsituted, alkoxyalkyl having 
from 3 to about 24 carbon atoms, and benzyl which may optionally be 
ring-substituted with halogen or lower alkyl having from 1 to about 6 
carbon atoms; 
R.sup.2 is selected from the group consisting of hydrogen hydroxyphenyl 
which may be ring-substituted, and an acyclic ether selected from the 
group consisting of (i) alkoxy represented by --OR.sup.3, wherein R.sup.3 
represents alkyl having from 1 to about 12 carbon atoms, alkoxyalkyl 
having from 2 to about 24 carbon atoms, phenyl which may be substituted, 
benzyl or substituted benzyl, heteroaryl or substituted heteroaryl; (ii) 
polyalkoxy represented by the structure CH.sub.3 --OCH.sub.2 CH.sub.2 
].sub.n' wherein n' is an integer in the range from 1 to about 20; and 
(iii) R.sup.4 --O--R.sup.5 wherein either R.sup.4 or R.sup.5 is a linking 
group selected from phenyl and benzyl, each of which may be substituted, 
alkyl having from 1 to about 24 carbon atoms, and cycloalkyl having from 3 
to about 7 ring carbon atoms one or more of which may be substituted; and, 
R.sup.1 may be substituted with R.sup.2, and if so substituted, each 
R.sup.2 substituent may be the same or different; 
whereby said pyrrole polymer formed has a conductivity in the range from 
about 10.sup.-3 to about 150 ohm.sup.-1 cm.sup.-1 ("S/cm"). 
It is also a general object of this invention to convert an insulating 
susbtrate having a conductivity in the range from about 10.sup.-15 to 
10.sup.-6 S/cm into a conductive substrate having a conductivity in the 
range from 10.sup.-3 to about 150 S/cm, by applying to the substrate a 
conductive deposit of finely divided particulate PP/subs PP formed by the 
process of my invention. 
It is another general object of this invention to provide a conductive 
PP/subsPP which has only a Cl or Br counterion and essentially no Group 
VIII metal ion, simply by conducting the polymerization reaction in a 
coordinating solvent such as acetonitrile. A coordinating solvent is one 
which can form a covalent bond with the Group VIII metal. The polymer so 
formed, indicated by PP/subsPP.sup.+ Cl.sup.-, or PP/subsPP.sup.+ 
Br.sup.-, is compactable, has high conductivity, and excellent 
compatibility with a human body in which it may be implanted. 
It is a specific object of this invention to provide a process in which the 
conductivity of a PP/subs PP, as a shaped article formed by compaction, or 
as a conductive deposit applied to a substrate, may be tailored to produce 
(i) a semiconductor (10.sup.-3 to 1 S/cm) by maintaining a molar ratio of 
initiator to pyrrole monomer in the range of from about 0.1 to about 1, 
more preferably about 0.25 to 1; and (ii) a conductor (1 to 150 S/cm) by 
maintaining a molar ratio of initiator to pyrrole monomer in the range 
from 1 to about 20, more preferably 1 to about 10, in a saturated solution 
of initiator in liquid reaction medium. 
It is another specific object of-this invention to provide a process in 
which one may produce a PP/subs PP conductor by maintaining the 
aforespecifed molar ratio in a dialkyl ether reaction medium in which 
FeCl.sub.3 (anhyd) is soluble, as is the monomer, so that a maximum value 
of S/cm is reached within a relatively short time after commencement of 
the reaction, after which time, the value diminishes, which general 
relationship of S/cm as a function of time is a unique characteristic of 
PP/subs PP produced by my process. 
It is also a specific object of this invention to provide a process for 
making conductive paper having a conductivity in the range from 10.sup.-3 
to about 150 S/cm for use in EMI shielding, battery and photovoltaic 
applications, antistatic packaging, and, backing for dielectric paper, 
inter alia. 
It is a further specific object of this invention to provide a synthetic 
resinous insulating substrate such as poly(vinyl chloride) with a 
conductive surface; and, insulating inorganic solid filler materials such 
as aluminum trihydrate, glass spheres or fibers and the like with a 
conductive coating.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
The conductive polymer of this invention may be represented by the 
structure: 
##STR2## 
wherein, 
n is an integer in the range from 2 to about 100, and more preferably in 
the range from about 5 to about 20; 
M represents a Group VIII metal selected from the group consisting of iron, 
nickel and cobalt; 
X represents chorine or bromine; 
R.sup.1 and R.sup.2 have the same connotation as that given hereinbefore. 
In the process of this invention, a finely divided compactable PP/subs PP 
is precipitated from a liquid reaction medium in which the polymerization 
of a pyrrole/subs pyrrole monomer having the structure (I) is carried out 
under anhydrous conditions. By "liquid reaction medium" I refer to an 
organic liquid which is essentially unreactive with the polymerization 
initiator, or the monomer, unless the reaction medium is a coordinating 
solvent. For the anhydrous FeCl.sub.3 Meek & Dragocoordination model, see 
"The Chemistry of Non-Aqueous Solvents" edited by J. J. Lagowski, Vol. I, 
Academic Press, New York (1966). By "anhydrous" conditions I refer to the 
reaction being carried out in the absence of moisture, particularly that 
the polymerization initiator be essentially free from bound water such as 
water of hydration. 
It is most preferred that the reaction medium be a solvent for either the 
initiator or the monomer, and most preferably, for both. Where the 
reaction medium is a solvent for neither, the initiator is preferably used 
as a finely divided powder having a particle size in the range from about 
5 microns to about 45 microns. When the reaction medium is a solvent for 
the initiator, it is preferred that the reaction medium be saturated with 
initiator. It is not essential that the initiator be highly soluble, and 
in most cases, the solubility is limited. By "soluble" I refer to 
initiators having a solubility in the range from about 5 to about 25 parts 
per hundred parts (pph) of solvent, a few initiators being more soluble. A 
solubility less than 5 pph is generally ineffective for the purpose of 
providing desirable speed of reaction. 
Preferred initiators are the halides of iron, cobalt and nickel, preferably 
the fluoride, chlorides and bromides. Where stable iodides are used, the 
reactivity is generally not comparable to the chlorides and fluorides 
which are more preferred, for example ferric chloride, nickel chloride and 
cobalt chloride, and ferric fluoride, cobalt fluoride and nickel fluoride, 
all in the +3 state. Less preferred are cobalt bromide and nickel bromide. 
The amount of the initiator used and its "freshness" generally controls the 
speed of the reaction and the molecular weight of the polymer, as is 
evidenced by the conductivity of the PP/subs PP formed. By "freshness" I 
refer to initiator which has not been aged, particularly by exposure to 
the atmosphere. If the initiator is essentially insoluble in the reaction 
medium, more initiator is generally required than if the initiator is 
soluble. Even when the initiator is soluble, it is preferably used in a 
major molar amount relative to the monomer, and preferably in the range 
from above 1 to about 20 moles of initiator to monomer, lesser ,amounts 
typically yielding a semiconductor polymer. Where the molar ratio of 
initiator to monomer is in the range from about 0.1 to about 1, and 
preferably from about 0.25 to 1, the polymer formed is a semiconductor. 
Where the molar ratio is in the range from 1 to about 20, and more 
preferably from 1 to about 10, the polymer formed is a conductor. 
Unless the reaction medium used is a coordinating solvent, the particular 
solvent used is not narrowly critical except to the extent that it 
influences the properties of the polymer obtained, the extent of the 
influence usually being determined by simple trial and error such as one 
in this art would routinely expect to do. 
A solvent in which there is no significant covalent bonding to the Group 
VIII metal of the initiator but nevertheless permits initiation of the 
polymer and its subsequent doping, is referred to herein as an "inert 
liquid" though it may have a solvating effect. 
Liquids in which the initiator is poorly if at all soluble include the 
alkanes such as hexane, and cycloalkanes such as cyclohexane, all having 
from 4 to about 8 carbon atoms; aromatic liquids such as benzene, toluene 
and xylene; methoxy-xylene, nitro-xylene; halogenated aromatic liquids 
such as chlorobenzene, chlorotoluenes and chloroxylenes; 
hydrohalomethylenes particularly hydrochloromethylenes; chloroform 
perchloroethylene and carbon tetrachloride; sulfolane, 1,4-dioxane and 
dimethyl sulfone; and, lower primary alcohols having from 1 to about 6 
carbon atoms; inter alia. Liquids in which the initiator is soluble 
include nitromethane and nitrobenzene; essentially unbranched dialkyl 
ethers having from 4 to about 20 carbon atoms, most peferably diethyl 
ether; propylene carbonate and N-methyl-2-pyrrolidone, and the like. 
Coordinating solvents preferred in the process for forming the Group VIII 
metal-free polymer are the lower alkyl (C.sub.1 -C.sub.5)nitriles, 
especially acetonitrile propionitrile and butronitrile. It is because of 
their coordination properties that such solvents essentially prevent the 
Group VIII metal ion from being associated with the conductive PP formed. 
The polymerization reaction may be carried out at room temperature, but is 
preferably carried out at slightly elevated temperature in the range froma 
bout 20.degree. C. to about 80.degree. C. The pressure is not critical and 
is usually atmospheric though subatmospheric pressures and elevated 
pressures as high as about 20 atm may be used, if desired. Reaction 
pressure is typically autogenous and the reaction proceeds under an inert 
gas (nitrogen) blanket. The reaction time is most preferably very fast, in 
the order of about 0.5 sec to about 5 see, and is essentially 
instantaneous particularly when the polymer is deposited on a substrate 
such as paper. 
The speed of the polymerization reaction where both the monomer and the 
initiator are in the liquid phase lends the reaction to a ready 
application to the impregnation of paper with conductive polymer in 
conventional paper making where a continuous sheet of paper is dipped 
first in monomer and then into an inert liquid containing initiator. All 
references to "monomer" herein refer to a pyrrole/subs pyrrole, and all 
those to "polymer" refer to PP/subs PP. Though porous substrates such as 
cellulosic and ceramic materials are preferred, semiconductors and 
conductors of this invention include any shaped article of ceramic or 
synthetic resinous material or any substrate which has been coated with 
polymer formed by the process of this invention. 
Electrically non-conducting organic materials which may be made conductive 
include copolymers of butadiene with acrylic acid, alkyl acrylates or 
methacrylates, polyisoprene, polychloroprene, and the like; polyurethanes; 
vinyl polymers known as PVC resins such as polyvinyl chloride, copolymers 
of vinyl chloride with vinylidene chloride, copolymers of vinyl halide 
with butadiene, styrone, vinyl esters, and the like; polyamides such as 
those derived from the reaction of hexamethylene diamine with adipic or 
sebacic acid; epoxy resins such as those obtained from the condensation of 
epichlorohydrin with bisphenols, and the like; ABS resins, polystyrene, 
polyacrylonitrile, polymethacrylates, polycarbonates, varnish, 
phenol-formaldehyde resins, polyepoxides, polyesters, and polyolefin homo- 
and copolymers such as polyethylene, polypropylene, ethylene-propylene 
polymers, ethylene-propylenediene polymers, ethylene-vinyl acetate 
polymers, and the like. 
Other organic insulators which can be made conductive include mixtures and 
blends of polymeric materials such as ABS resin blends, PVC and 
polymethacrylate blends, and blends of polyolefin homopolymers and 
copolymers such as blends of polypropylene in epdm polymers. 
A compact of conductive PP/subs PP polymer may be used in an animal body as 
an implantable biosensor. 
Inorganic insulating materials may also be made conductive or 
semiconductive. Such materials include fillers such as antimony oxide, 
aluminas, phosphates and the like, particularly those fillers used as fire 
retardants, and, insulating reinforcing materials such as glass spheres or 
fibers. Especially when the surface of glass fibers is treated, enough 
conductive polymer may be coated on the fibers so that when they are used 
to reinforce a shaped article of the synthetic resinous material, the 
article becomes conductive. 
The procedure for applying the PP/subs PP polymer to a substrate is simple: 
A substrate to be coated is simply soaked in monomer and dipped in a 
solution/suspension (either of which is broadly referred to herein as a 
dispersion) of anhydrous initiator such as FeCl.sub.3 in the reaction 
medium. Instantaneous polymerization occurs based on the 
oxidation-reduction potentials of the monomer/FeCl.sub.3 system. 
During polymerization, Fe and Cl are incorporated into the polymer as 
charged species, Fe being present in the range from about 3 to about 15% 
by wt of the polymer. If no charged species are present in the polymer, as 
is the case in neutral PP/subs PP formed particularly by 
electrodeposition, the polymer is an insulator. 
Where Fe and Cl are present in combination as charged species in my 
polymer, the desired conductivity in the stated range may be imparted to 
the polymer or substrate to which it is applied by tailoring the 
parameters of the system, at all times, of course, using the anhydrous 
initiator. Where only Cl or Br as the counterion is desired, the 
concentration of the initiator and the temperature of the reaction affect 
the conductivity obtained, but it is essential that the initiator be 
anhydrous. The absence of water in the initiator is the parameter never 
heretofore recognized as being result-effective to give the particular 
properties of conductive polymers formed by this invention. 
Quite surprising is that irrespective of the surface of the substrate, as 
long as it is essentially free of moisture, the polymer applied to the 
substrate is strongly adhered to it. The inertness of the polymer and its 
insolubility in commonly available solvents under acid or base conditions, 
ensures that the conductivity of the coated substrate will survive for a 
long period of time. 
The amount of polymer deposited on the substrate may be controlled so that 
from about 0.001% to about 25% by wt of the substrate is polymer, in most 
instances from 0.1% to about 5% by wt being adequate to provide the 
desired conductivity. 
Quite noteworthy is that when the substrate is first soaked in the 
dispersion, whether solution or suspension, of initiator in reaction 
medium, then dipped in pyrrole/subs pyrrole monomer, the formation of 
polymer is slower than when the order of the steps is interchanged, and 
the conductivity of the polymer is generally in the semiconductor range or 
lower. Thus, the conductivity of the polymer, or the substrate to which 
the polymer is applied, may be tailored by a choice of whether the monomer 
is added to liquid containing the initiator, or whether the liquid 
containing initiator is added to the monomer. Of course where the 
substrate is to be made highly conductive quickly, the substrate will be 
first coated with monomer and then dipped into liquid containing initiator 
for speed of reaction and higher conductivity; and, for a semiconductor, 
substrate is first coated with initiator, then dipped into monomer so as 
to have lower conductivity. 
When the polymer is desired in a finely divided particulate form, monomer 
is simply poured into the dispersion of initiator. Again, as might be 
expected, the conductivity of the polymer as measured from a compact of 
the powder, will vary depending upon the process conditions particularly 
the ratio of initiator to monomer, the physical properties of the inert 
liquid, and the temperature at which the polymerization reaction takes 
place. 
The invention is more fully described by the following illustrative 
examples. 
EXAMPLE 1 
Oxidative Polymerization of Pyrrole 
19.6 g (0.12 mole) of fresh anhydrous FeCl.sub.3 is dispersed in 300 ml of 
anhydrous diethyl ether in which some of the FeCl.sub.3 is dissolved so as 
to form a saturated solution, while stirring under a N.sub.2 atmosphere at 
22.degree. C. To this stirred saturated solution is added 2.1 ml (0.03 
mole) of freshly distilled pyrrole in one portion. The reaction mixture 
instantly acquires a black color and a slight exotherm results. After 
allowing the reaction to proceed for 1 hr at 22.degree. C. the black 
precipitate is filtered and washed with water, then with 50 ml of 10% HCl 
and again with water until the washings register about ph 7. It is 
essential that dilute HCl, preferably less than 20%, and not cone HCl, be 
used to preserve the charged species of Fe and Cl in combination. Finally, 
the black polymer is washed with ethanol and diethyl ether and dried for 4 
hr in vacuo at 65.degree. C. The product yield is 2.77 g. 
A measurement of the DC four-point probe conductivity of the black powder 
gives a value of 46 S/cm at 22.degree. C. 
Elemental analysis (% by wt) of the PP product is made for C and H together 
in a modified Perkin Elmer 240 Analyzer as described in The Microchemical 
Journal, Vol 24, No 3, pg 300 et seq (September 1979). O is determined by 
a CO.sub.2 coulometer as is conventionally done. N is measured by a 
modified Dumas system. Fe is determined by atomic absorption; and, Cl by 
the Schoniger oxygen flask combustion method. The analysis is as follows: 
______________________________________ 
Found (% by wt) 
______________________________________ 
C = 51.96 
H = 3.89 
N = 14.88 
Fe = 7.17 
Cl = 13.41 
O = 8.69 
______________________________________ 
The oxygen in the forgoing analysis derives from the wash water trapped 
with the PP, which has a well known proclivity for O. Because the atomic 
ratio of Cl to Fe is closer to 3 than to 4, the calculated analysis 
(below) is based on C.sub.4 H.sub.3 N(FeCl.sub.3).sub.0.12..0.5H.sub.2 O, 
the water being derived from washing, and is as follows: 
______________________________________ 
Calculated (% by wt) 
______________________________________ 
C = 51.35 
H = 4.32 
N = 14.98 
Fe = 7.16 
Cl = 13.64 
O = 8.55 
______________________________________ 
EXAMPLE 2 
Low Temperature Oxidative Polymerization of Pyrrole 
39.2 g (0.242 mole) of fresh anhydrous FeCl.sub.3 is dispersed in 600 ml of 
anhydrous diethyl ether in which some of the FeCl.sub.3 is dissolved so as 
to form a saturated solution, while stirring under a N.sub.2 atmosphere at 
22.degree. C. This solution is chilled to 0.degree. C. and to this chilled 
and stirred saturated solution is added 4.2 ml (0.61 mole) of freshly 
distilled (from KOH) pyrrole, at 0.degree. C., in a single portion. The 
reaction mixture instantly acquires a black color and reaches about 
8.degree. C. due to the exotherm. After allowing the reaction to proceed 
for 1 hr at 0.degree. C. with stirring, the black precipitate is filtered 
and washed with distilled water, then with 100 ml of 10% HCl, until the 
washings register about pH 7. Finally, the black polymer is rinsed with 
ethanol and then diethyl ether and dried for 4 hr in vacuo at 65.degree. 
C. The product yield is 4.77 g (dry wt). 
A measurement of the DC four-point probe conductivity of the black powder 
gives a value of 90 S/cm at 22.degree. C. 
Because the atomic ratio of Cl to Fe is closer to 4 than to 3, the 
calculated analysis (below) is based on C.sub.4 H.sub.3 
N(FeCl.sub.4).sub.0.07.0.4H.sub.2 O, the water being derived from washing, 
and, the analysis made in a manner analogous to that described hereinabove 
is as follows: 
______________________________________ 
Calculated 
Found (% by wt) (% by wt) 
______________________________________ 
C = 56.11 C = 55.78 
H = 3.85 H = 4.46 
N = 15.95 N = 16.27 
Fe = 4.37 Fe = 4.54 
Cl = 12.44 Cl = 11.53 
O = 6.94 O = 7.43 
______________________________________ 
EXAMPLE 3 
Oxidative Polymerization of 3-methyl-4-hexyloxyphenyl Pyrrole 
In a manner analogous to that described in example 1 hereinabove, 2.52 g 
(0.0155 mole) of fresh anhydrous FeCl.sub.3 is dispersed in 30 ml of 
anhydrous diethyl ether at 22.degree. C. under a N.sub.2 atmosphere. 1.0 g 
(0.00388 mole) of 3-methyl-4-hexyloxyphenyl pyrrole is dissolved in 10 ml 
of anhydrous diethyl ether and this solution added to stirred FeCl.sub.3 
solution. The black polymer formed is worked up with washing in water and 
then dilute mineral acid to yield 0.65 g of product which is a black 
free-flowing powder. This powder is soluble in several organic solvents, 
particularly lower alkanos having from 1 to about 6 carbon atoms, and 
ethers having less than 20 carbon atoms. A measurement of the DC 
four-point probe conductivity of the powder gives a value of 
8.times.10.sup.-3 S/cm at 22.degree. C. 
Because the atomic ratio of Cl to Fe is closer to 4 than to 3, the 
calculated analysis (below) is based on C.sub.17 H.sub.21 
NO(FeCl.sub.4).sub.0.22.0.4H.sub.2 O, the water being derived from 
washing, and, the analysis made in a manner analogous to that described 
hereinabove is as follows: 
______________________________________ 
Calculated 
Found (% by wt) (% by wt) 
______________________________________ 
C = 65.81 C = 66.70 
H = 6.85 H = 7.19 
N = 4.71 N = 4.58 
O = 7.39 O = 7.32 
Fe = 4.37 Fe = 4.54 
Cl = 12.44 Cl = 11.53 
______________________________________ 
The structure, confirmed by IR and NMR analysis, is as follows: 
##STR3## 
EXAMPLE 4 
Oxidative Polymerization of 3-methyl-4-phenyl Pyrrole 
In a manner analogous to that described in example 3 hereinabove, 4.15 g 
(0.026 mole) of fresh anhydrous FeCl.sub.3 is dispersed in 50 ml of 
anhydrous diethyl ether at 22.degree. C. under a N.sub.2 atmosphere. This 
solution is chilled to 0.degree. C. and to it is added 1.0 g (0.0064 mole) 
of 3-methyl-4-phenyl pyrrole dissolved in 14 ml of anhydrous diethyl ether 
which has been chilled to 0.degree. C. The reaction mixture turns black 
and the temperature rises to about 6.degree. C. The black polymer formed 
is worked up with washing in water and then dilute mineral acid (50 ml of 
10% HCI solution) to yield, after drying, 1.1 g of product. This product 
is a solid particulate material which is soluble in organic solvents, 
particularly halocarbons such as dichloromethane, lower alkanols and 
ethers such as tetrahydrofuran. A measurement of the DC four-point probe 
conductivity of the powder gives a value of 4.3.times.10.sup.-3 S/cm at 
22.degree. C. 
Because the atomic ratio of Cl to Fe is about 3.8, the calculated analysis 
(below) is based on C.sub.11 H.sub.9 N(FeCl.sub.3.8).sub.0.11.0.9H.sub.2 
O, the water being derived from washing, and, the analysis made in a 
manner analogous to that described hereinabove is as follows: 
______________________________________ 
Calculated 
Found (% by wt) (% by wt) 
______________________________________ 
C = 68.01 C = 68.67 
H = 4.66 H = 5.67 
N = 7.14 N = 7.28 
O = 7.25 O = 7.48 
Fe = 2.98 Fe = 3.19 
Cl = 7.04 Cl = 7.70 
______________________________________ 
EXAMPLES 5-11 
Effect of FeCl.sub.3 conc. in the Reactor 
In the following examples, the concentration of finely divided anhydrous 
FeCl.sub.3 initiator in solution in diethyl ether anhydrous inert liquid 
medium is varied in the range from 1 to 8 moles of FeCl.sub.3 per mole of 
pyrrole monomer, the volume of diethyl ether being held constant at 300 
ml, without regard to the amount of initiator which goes into solution. 
Generally, the volume of inert liquid used is based on the volume of 
initiator used. Since, to make polymers having the desired range of 
conductivity, at least 0.1 mole of initiator per mole of monomer is used, 
at least an equal volume of initiator and inert liquid is necessary. A 
volume ratio of 100 (inert liquid to initiator) results in too slow a 
reaction, and a ratio less than 1 is impractical. Thus, since the reaction 
is carried out in a liquid medium, and the ratio of initiator to monomer 
is the prime determinative factor for the conductivity of the polymer 
formed, a preferred range for the volume ratio of inert liquid to 
initiator is from about 1:1 to about 100:1, more preferably about 5 to 
about 50, without regard to the amount of initiator which goes into 
solution. With 300 ml diethyl ether, a saturated solution of FeCl.sub.3 is 
formed at a molar ratio of about 4, portion of the FeCl.sub.3 being 
dispersed in the ether at higher ratios. All polymerizations in Table I 
herebelow are carried out at 22.degree. C., and DC, four-point probe 
conductivities are measured at 22.degree. C. 
TABLE I 
______________________________________ 
mole ratio conductivity 
Ex. No. FeCl.sub.3 /pyrrole 
S/cm 
______________________________________ 
5 0.5 1 .times. 10.sup.-3 
6 1 1 
7 2 5 
8 3 20 
9 4 40 
10 4* 90 
11 8 34 
______________________________________ 
*polymerization carried out at 0.degree. C. 
As will be evident from the foregoing Table I, a molar ratio greater than 4 
appears to yield a reaction product having about the same conductivity as 
that obtained with a ratio of 4, at 22.degree. C., but the conductivity is 
increased when the reaction is carried out at 0.degree. C. 
EXAMPLES 12-19 
Effect of Time of Polymerization Reaction on Conductivity of Polymer 
The following results are particularly noteworthy because known conjugated 
conductive polymers exhibit an increased level of electrical conductivity 
when the time of exposure to the oxidant (dopant) is increased. In the 
following series of experiments, the inert liquid medium was diethyl ether 
and its volume in each case was 300 ml though the ratio of FeCl.sub.3 to 
pyrrole was varied in the range from 4:1 to 1:1. DC four-point probe 
conductivity measurements in the following Table II were carried out on 
pressed powder discs at 22.degree. C. 
TABLE II 
______________________________________ 
mole ratio reaction time 
conductivity 
Ex. No. FeCl.sub.3 /pyrrole 
(hr) S/cm 
______________________________________ 
12 4 66 0.05-0.3 
13 4 4 5.9 
14 4 1 42 
15 3 48 0.05 
16 3 1 16 
17 2 68 0.005 
18 1 70 -0.014 
19 1 1 2.6 
______________________________________ 
EXAMPLE 20 
Insulator Substrates Made Conductive 
A. A strip of filter paper (Whatman #4) is soaked in anhydrous pyrrole and 
the excess wiped off. The pyrrole-soaked paper is dipped in a dispersion 
of 45 g of FeCl.sub.3 in 300 ml diethyl ether and immediately withdrawn. 
The paper instantaneously acquires the black color characteristic of PP. 
After washing with water, methanol and ether, the paper substrate coated 
with the polymer is allowed to dry for 1 hr and the conductivity measured 
at 22.degree. C. as in the previous examples. The value obtained is 10 
S/cm. 
B. In a manner analogous to that described immediately hereinabove, a strip 
of Geon.RTM. 103 EP poly(vinyl chloride) (PVC) film 6 mils thick, which is 
commercially available, is soaked in anhdyrous pyrrole for 30 min. The 
pyrrole-soaked PVC film is wiped to remove excess pyrrole and dipped into 
saturated initiator solution such as is used in 20A. As before, the film 
instantly acquires a balck color indicating the substrate has been coated 
with PP. The film is withdrawn, washed with water, methanol and ether and 
allowed to dry for 1 hr. The conductivity obtained was 1.38 S/cm. 
In an analogous manner, materials such as glass fibers which are insulators 
at ambient temperatures may be made conductive or semiconductive, as 
desired. Though this process lends itself particularly well to applying 
conductive PP/subs PP to laminar articles, they may be of arbitrary shape, 
and it is not critical how the pyrrole is applied to the article, or 
whether the pyrrole-coated article is dipped into the initiator solution. 
For example, either one, or both the pyrrole and the initiator solution 
may be sprayed onto the substrate before polymerization. 
EXAMPLE 21 
Conductive Fillers (Reinforcing) for Masking Filled (Reinforced) Polymers 
A. 30 g of antimony oxide (Sb.sub.2 O.sub.3) flour having a primary 
particle size in the range from about 1-5 microns is soaked in pyrrole, 
the excess pyrrole centrifuged off, and the pyrrole coated flour stirred 
into saturated initiator solution such as was used in 20A. Soon thereafter 
the solution is filtered, and the black powder obtained is worked up as 
before by washing, and dried. 20 g of the coated flour are milled with 100 
g of PVC and extruded into a thin sheet 6 mils thick. The sheet is 
conductive (about 5 S/cm) and the flame retarding characteristics of the 
flour are maintained. 
B. 20 g of Sb.sub.2 O.sub.3 flour are milled into 100 g of PVC and extruded 
into a film 6 mils thick. The filled film is then treated as described in 
example 20B hereinabove. The conductivity obtained is about 4 S/cm. 
C. 40 g of alumina trihydrate having a primary particle size in the range 
from about 1-45 microns is soaked in pyrrole as described in 21A 
hereinabove, the excess pyrrole removed, and the coated powder is stirred 
into initiator solution, filtered and dried. 20 g of the alumina 
trihydrate coated with PP are milled into PVC and extruded into 6 mil 
thick film. The film obtained has a conductivity of about 4 S/cm and the 
flame retarding qualities of the alumina trihydrate are retained. 
D. 20 g of alumina trihydrate powder are milled into 100 g of PVC and 
extruded into 6 mil thick film. The filled film is then treated as 
described in example 20A hereinabove. The conductivity obtained is about 5 
S/cm. 
In the foregoing examples 21C and D, the presence of water chemically bound 
in the alumina trihydrate does not appear to affect the effectiveness of 
the process because the water is not available for removal by the 
anhydrous inert liquid medium. 
Glass or other fibers made from refractory ceramic materials may 
analogously be first coated with PP and then used for reinforcing polymer, 
or, the fibers may first be incorporated in the polymer to reinforce it, 
then the reinforced polymer is coated with PP, though it will be 
appreciated the conductivities obtained in each case win be different. 
From the data presented in Table I it is evident that conductivity is 
increased at lower polymerization temperatures, but the rate of 
polymerization decreases. The polymerization may be carried out at any 
temperature above the freezing point of the inert liquid, but in practice, 
a temperature in the range from about -50.degree. C. to about 35.degree. 
C., more preferably from -20.degree. C. to 30.degree. C., is preferred. 
It will also be evident that the conductivity of PVC is substantially the 
same whether the conductive powder fillers are milled into the PVC before 
it is extruded; or, the PVC is milled with insulating powder, extruded, 
and then coated with PP. Much greater differences in conductivity are 
obtained with substrates which are coated with pyrrole first, then dipped 
into the initiator solution, and vice versa. 
EXAMPLE 22 
Preparation of PP.sup.+ Cl.sup.- (Polypyrrole Chloride) in Acetonitrile 
300 ml anhydrous FeCI.sub.3 and 300 ml of dry acetonitrile are stirred at 
reflux for 1 hr under a N.sub.2 blanket. The dark brown-red mix is cooled 
to room temperature. 2.1 ml of pyrrole freshly distilled over KOH is now 
added in a single portion. The mix turns black instantly and an exotherm 
to 27.degree. C. is noted. The reaction is continued for 1 hr at ambient 
conditions under N.sub.2 and protected from light. The reaction mixture is 
filtered, and the black precipitate is washed with copious amounts of 
water until neutral to pH paper, then rinsed with ethanol, then ether. The 
precipitate is then dried under vacuum at 65.degree. C. and weighed. 1.15 
g is recovered. The conductivity of the precipitate when compacted is 
about 0.27 S/cm. 
The following results are obtained upon analysis: 
______________________________________ 
Found (% by wt.) 
Structure: 
______________________________________ 
##STR4## 
##STR5## 
______________________________________ 
The foregoing corresponds to the empirical formula C.sub.4.2 H.sub.3.67 
N.sub.1.0 O.sub.0.53 Cl.sub.0.35 
EXAMPLE 23 
Preparation of PP in Aqueous Acid 
______________________________________ 
Reagents: Pyrrole (distilled over KOH) = 2.1 ml 
______________________________________ 
FeCl.sub.3.6H.sub.2 O 10.0 g 
0.01 M HCl 100 ml 
______________________________________ 
When the 0.01M HCl solution is stirred with the FeCl.sub.3.6H.sub.2 O added 
to it, a brown solution results at room temperature under N.sub.2. To this 
solution is added all the pyrrole. The mixture turns black instantly and 
the temperature rises to 28.degree. C. The reaction is continued for 1 hr 
at ambient conditions under N.sub.2 while being protected from light. The 
mixture is then filtered, the black precipitate is washed with water, then 
rinsed with ethanol, and finally with ether. The precipitate is then dried 
under vacuum at 65.degree. C. The yield of precipitate is 1.12 g. The 
conductivity of a compact of the polymer is found to be about 16 S/cm. 
Compared to an analogous reaction carried out in anhydrous diethyl ether 
with anhydrous FeCl.sub.3, the yield under anhydrous conditions is about 
60% better, and the conductivity is about 70% better. 
EXAMPLE 24 
Preparation of PP with Anhydrous and Hydrated FeCl.sub.3 for Comparison 
A. 32.7 g of FeCl.sub.3.6H.sub.2 O (0.12 mol FeCl.sub.3) is weighed into a 
reactor under a N.sub.2 blanket, 300 ml ether is added (under N.sub.2) and 
the mix stirred for 30 min while the mixture is protected from light. 2.1 
ml of pyrrole is dumped into the reactor and the reaction continued for 1 
hr at ambient temperature. Thereafter the black reaction mixture is 
filtered with difficulty. Addition of HCl, and allowing it to stand 
overnight, facilitates filtration. The precipitate obtained is washed well 
with water, then with ethanol and finally with ether before it is dried in 
vacuum at 65.degree. C. 0.65 g precipitate is recovered. The conductivity 
of a compact of the precipitate is about 0.1 S/cm. 
B. In an analogous manner to that described immediately hereinabove, 2.1 ml 
of pyrrole in anhydrous diethyl ether containing 0.12 mol anhydrous 
FeCl.sub.3 are reacted, and the precipitate recovered by washing and 
filtering, as described. The amount of precipitate recovered is 2.8 g. The 
conductivity of a compact of the precipitate is 50 S/cm. 
A comparison indicates that the yield with hydrated FeCl.sub.3 is much 
lower (4 times worse), as is the conductivity (500 times less). 
EXAMPLE 25 
Preparation of PP in Presence of Aqueous HCl Acid 
19.6 g of FeCl.sub.3 are stirred into 300 ml of water to which 15 ml of 
conc HCl are added. The solution temperature rises to about 35.degree. C. 
and the pyrrole is added in a single portion. The mixture turns black 
instantly, and the reaction is continued for 1 hr at ambient conditions 
under N.sub.2 and protected from light. After 1 hr a black precipitate is 
recovered which is rinsed with 10% HCl, washed with water, then rinsed 
sequentially with ethanol and ether. After drying at 65.degree. C. under 
vacuum 2.84 g of ppte is recovered. A compact of the polymer has a 
conductivity of 7 S/cm which is lower than that obtained under acid-free 
anhydrous conditions. 
It will be evident that the charges depicted on the conductive PP/subs PP 
are not quantitative. The counterions when the Group VIII metal is Fe may 
be FeCl.sub.4.sup.-, FeCl.sub.4 (2.sup.-) or FeCl.sub.6 (3.sup.-). 
EXAMPLE 26 
Preparation of Conductive Porous High Density Polyethylene ("PE") 
Though the anhydrous initiator may be deployed in a wide assortment of 
anhydrous liquid media which are inert relative to the initiator, the 
di(lower alkyl) ethers, for example diethyl ether is used herein because 
it is easily available and convenient to use. 
A porous polyolefin article of arbitrary shape, for example a piece of 
porous high density PE sheet (from Porex Technologies), is an insulating 
material having essentially infinite surface resistivity, at least a 
conductivity of less than 10.sup.-10 S/cm. A small 1.25" (inch) square 
sheet of the PE weighing 1.04 g and having a thickness of 0.065" with a 
pore size of 70 microns, was soaked in 8 ml of pyrrole for 1 hour at 
22.degree. C. The excess pyrrole was wiped off and the porous PE was found 
to have absorbed 0.918 g of pyrrole. The pyrrole-impregnated PE was then 
suspended in a solution containing 9.8 g of anhydrous FeCl.sub.3 in 150 ml 
of diethyl ether. The pyrrole impregnated PE acquired a black color 
characteristic of PP formation. After 1 hour of immersion, the black, 
PP-coated PE was removed from the FeCl.sub.3 /ether solution and it was 
washed with water and rinsed with ethanol and ether. After vacuum drying 
at 65.degree. C., the PP-coated PE was found to weigh 1.08 g. 
The surface resistivity of the coated sample was found to be 360 
ohms/square for a sample thickness of 0.066". Note that the 
pyrrole-impregnated PE gained only 4% in weight, and increased only 1.5% 
in thickness as a result of the impregnation process. Thus, the porous PE 
has essentially retained its original dimensions and weight while 
acquiring substantial conductivity. The porous PP-coated PE is used as a 
separation membrane, filter or sensor. 
EXAMPLE 27 
Preparation of Conductive Poly(Vinyl Chloride) ("PVC") Molding Resin 
8.62 g of commercially available Geon.RTM. PVC having an average particle 
size of 120 microns and a porosity of 0.25-0.33 cc/g DOP, are soaked in 
liquid pyrrole for 30 min at 22.degree. C. The excess pyrrole liquid is 
filtered off under suction, and the PVC resin is found to have absorbed 
8.654 g of pyrrole monomer. A 2 g sample of this pyrrole-impregnated PVC 
resin is then added in a single portion to a solution of 9.8 g of 
anhydrous FeCl.sub.3 in 150 ml of diethyl ether. The pyrrole-impregnated 
PVC resin instantaneously acquires the black color characteristic of PP. 
After stirring the reaction mixture for 1 hr at 22.degree. C. under 
nitrogen, the solution is filtered off and the black PP-coated PVC resin 
is washed with water, 10% HCl, water, ethanol and ether, in that order, 
and dried in vacuo for 1 hr at 65.degree. C. Conductivity is measured with 
a DC four-point probe at 22.degree. C. on a compacted disc of the 
PP-coated resin granules. The value obtained is 22 S/cm. 
EXAMPLE 28 
Preparation of Conductive Zeolite Particles 
2.0 ml of liquid pyrrole were added in a single portion to a stirred 
suspension of 2.0 g of zeolite (ZLD 1000, Union Carbide) in 150 ml of 
diethyl ether. This mixture was allowed to stir at 22.degree. C. under 
nitrogen for 36 hr to allow complete sorption (absorption and adsorption) 
of the pyrrole monomer into and onto the porous zeolite. 19.6 g of 
anhydrous FeCl.sub.3 were then added to the reaction mixture. The zeolite 
material instantly acquired the black color characteristic of PP 
formation. The mixture was filtered and the black, PP-impregnated and 
coated zeolite was washed extensively with water, ethanol and ether, in 
that order. The product was vacuum-dried at 65.degree. C. to give 3.3 g of 
PP-impregnated zeolite. 
Conductivity measured with a DC four-point probe is 1.62.times.10.sup.-2 
S/cm at 22.degree. C., as compared with a value of less than 10.sup.-6 
S/cm for the as-received, uncoated zeolite. 
The foregoing PP-coated zeolite is used as a catalyst and/or 
catalyst-support for electrocatalytic reactions, and as an ion-exchange 
material. 
EXAMPLE 29 
Preparation of an Optical Storage Device 
A chemically synthesized PP film may be used to produce "write-once" 
optical data storage devices. An optically flat substrate, for example a 
smooth PVC disc, is contacted with a solution of an oxidant/polymerization 
initiator by dipping, spraying, brushing or otherwise coating the solution 
onto the disc. The preferred oxidant/initiator is anhydrous FeCl.sub.3 
/diethyl ether. The coated disc is exposed to pyrrole vapor resulting in 
instantaneous formation of a black coating of PP on the disc. 
Spectroscopic analysis of the black PP film indicates a high degree of 
absorption across the ultraviolet-visible-infrared region, that is, from 
200-2000 nanometers. A laser beam from any of various laser sources for 
example, argon, helium-neon, or diode, of sufficient power, may be used to 
record (write) information onto the PP-coated disc. The laser beam, when 
directed onto the black surface, converts the PP film to a highly 
reflective spot. As a result, a high degree of spectral contrast is 
provided by virtue of the highly absorbing surface of the non-exposed PP 
film and the highly reflective laser beam-exposed spots. The exposed disc, 
now inscribed with the information written with the laser beam, can then 
be read using a low power laser, in a conventional manner. 
The foregoing process has several advanatges compared with one described in 
a recent journal article relating to an information storage device based 
on electrochemically synthesized PP film (see "Polypyrrole for Use in 
Information Storage" by W. H. Meyer, Synthetic Metals, 10, 255-259, 1985). 
For example, the electrochemical synthesis of PP requires long reaction 
times (90 min or more), is energy intensive, and the PP film dimensions 
are limited to the size/shape of the electrode utilized in the 
electrochemical cell. In addition, the electrochemically prepared PP film 
must subsequently be laminated (by gluing or hot-pressing) onto the 
substrate, thereby making the information storage device so formed highly 
susceptible to failure as a result of likely delamination. 
In contrast, my one-step process for making a PP-film coated optical disc 
is characterized by essentially instantaneous formation of the PP film. 
Since the PP is grown directly onto the substrate, a separate lamination 
step is avoided as is the risk of delamination. My process is amenable to 
deposition of PP onto any substrate of arbitrary size and shape as long as 
it does not interfere with the formation of the PP; the process is not 
energy intensive, and is well-adapted for mass production of optical 
storage devices. 
EXAMPLE 30 
Metallization of Polyprrole-Impregnated Filter Paper 
A piece of filter paper (Whatman #2) was made conductive by impregnating it 
with PP as described in Example 20A above, then immersed in a solution 
containing 2.0 g AgNO.sub.3, 3 ml of 28% NH.sub.4 OH and 50 ml water at 
22.degree. C. To the above solution was added 3.5 ml of 37% formaldehyde 
in 50 ml water. The black PP-coated filter paper instantaneously acquired 
a silver sheen as a layer of elemental silver was deposited on the paper. 
The conductivity of the paper was essentially that of silver, that is 
about 10.sup.6 S/cm. 
EXAMPLE 31 
PP-impregnated Filter Paper used as a Sensor 
A piece of 200 ohms/square PP-impregnated filter paper, prepared according 
to the procedure described in example 20A hereinabove, is exposed to 
flowing HCl gas for 30 min, after which it has a surface resistivity of 
120 ohms/square. 
In an analogous manner, a 125 ohms/square piece of PP-impregnated filter 
paper after being exposed to gaseous ammonia for 30 min, has a surface 
resistivity of 2,500 ohms/square. 
The foregoing are each examples of a PP-impregnate substrate undergoing a 
change in surface resistivity when contacted with various chemical agents. 
The magnitude and direction of the the change in surface resistivity, 
whether to greater or lesser conductivity, is a characteristic of the 
chemical agent which can therefore be detected by exposure to the 
PP-impregnated substrate. 
From the foregoing examples it will be evident that the chemical oxidative 
polymerization of pyrrole to impregnate or otherwise coat an insulating 
substrate to convert it to a conductive one, allows one to convert large 
and/or complex parts of arbitrary shape which retain their mechanical 
properties. In other words, they are converted to semiconductors or 
conductors without affecting the physical properties of the substrate. 
This is is marked contrast to electrochemical polymerization of PP which 
requires the use of a conductive substrate (electrode) and the shape and 
size of the article to be coated is limited by the dimensions of the 
electrode which can be used in the electrochemical process. 
A teaching of the electrochemical process is found in U.S. Pat. No. 
4,582,575 to Warren et al (class 204/subclass 12) in which an electrically 
conducting composite is formed by tightly overlaying a dielectric porous 
substance on an anode in an electrolytic cell containing pyrrole monomer 
and a non-nucleophilic anion. Examples of such anions are bisulfate anions 
derived from sulfuric acid or sodium bisulfate. After electrolysis, the 
polymer impregnated insulating material is peeled from the anode. 
It was thereafter, and much later, discovered that the electrochemical 
process had unacceptable limitations, and a non-electrochemical process 
was disclosed in U.S. Pat. No. 4,696,835 to Maus et al (class 427/subclass 
121). In this '835 process, the dielectric substrate is contacted with a 
strong oxidant capable of oxidizing the pyrrole monomer to PP; the 
substrate is then dried and exposed to vapors of pyrrole which are 
converted in the presence of a non-nucleophilic anion into PP which is 
deposited on the substrate. 
In U.S. Pat. No. 4,697,000 to Witcuki et al (Class528/subclass 423) there 
is claimed a process for producing electrically conducting pyrrole powder 
by treating liquid pyrrole with a solution of a strong oxidant which is a 
cation and oxidizing the pyrrole with this cation in the presence of a 
non-nucleophilic anion. Cations identified are Fe.sup.3+, Cu.sup.2+, 
Ce.sup.+, NO.sup.+, NO.sub.2.sup.+ and (C.sub.6 H.sub.5).sub.3 C.sup.+ 
which appear to be effective both in the presence of water, and when no 
water is stated to be present. No mention is made as to the effect of the 
presence of water, nor is there any mention of the formation of a 
metal-containing anion in an organic anhydrous solvent, which anion would 
not likely be non-nucleophilic. In U.S. Pat. No. 4,697,001 to Walker et al 
(class 528/subclass 423) the conductive pyrrole was produced with the 
foregoing cations but using a large organic anion (referred to as an 
oxidant counterion). Such anions are identified as being alkyl and aryl 
sulfonates and fluorinated carboxylates. For example, ferric 
ethylbenzenesulfonate in aqueous solution is used; in another, the 
reaction was carried out in methanol. To impregnate a substrate, a 
two-step procedure is used: first, the substrate is wetted with a solution 
of ferric ethylbenzenesulfonate in acetone; in the second step the wetted 
substrate is dipped into a solution of pyrrole in pentane. 
General Applications for PP-coated/impregnated substrates which were 
Insulators: 
1. antistatic packaging and EMI shielding; 
2. coating fibers to produce conductive composites for aerospace 
applications, for example, to be used in protection of aircraft from 
damage due to being struck by lightning; and, masking aircraft against 
detection by radar; 
3. chemical sensors, because the conductivity of PP changes upon exposure 
to different chemicals; 
4. electrically conductive membranes for use in separation processes and 
for controlled release drugs; 
5. electrocatalysis/photocatalysis; 
6. Schottky barriers; 
7. electroless plating; 
8. patterned electrodes; 
9. high-density information storage devices; 
10. built-in heating devices such as heated automobile seats, and de-icers 
for aircraft wings; 
11. lightweight, flexible batteries; 
12. providing flame-retardant fillers, reinforcing fibers and structures 
containing them with electrical conductivity by virtue of the conductivity 
of the fillers and fibers coated with the conductive PP. 
Having thus provided a general discussion, and specific illustrations of 
the best mode of my invention, it is to be understood that no undue 
restrictions are to be imposed by reason thereof except as provided by the 
following claims.