The invention relates to compositions of a soluble polyimide and polypyrrole. These compositions can preferably be prepared by anodic oxidation of pyrrole or a pyrrole derivative at electrodes coated with polyimide. They make it possible to prepare free standing electrically conductive films.

The present invention relates to polypyrrole/polyimide compositions, 
preferably polyimide films, which are modified by a polymerised or 
copolymerised pyrrole derivative, to a process for the preparation of said 
films, and to the use thereof as electrically conductive films or as 
composites. 
Polypyrrole films or films made from copolymers of pyrrole are known. These 
films have high electrical conductivity and are resistant to ambient 
conditions (air, moisture). However, the mechanical properties of these 
films are unsatisfactory. Polypyrrole films containing inorganic anions 
are brittle and tear easily under stress. This limits their usefulness for 
technical applications, as they can for example only be shaped with 
difficulty. There has therefore been no lack of attempts to improve 
polypyrrole films with respect to their technical application. 
German Offenlegungsschrift No. 3 227 914 discloses a process for processing 
polypyrrole, wherein the polymer is shaped under specific elevated 
temperatures under pressure and optionally with further substances. 
The preparation of electrically conductive films made from polypyrrole and 
other conventional insulating polymers, e.g. PVC, has already been 
reported on (q.v. Niwa and Tanamura, J. Chem. Soc. Chem. Comm., 1984, 817 
and De Paoli, Waltmann, Diaz and Bargon, J. Chem. Soc. Chem. Comm., 1984, 
1015). 
To this end, platinum electrodes are coated on the surface with a 1 to 10 
.mu.m thick polymer film and a current is applied to these anodes in an 
electrolytic cell. The electrolyte solution contains pyrrole. Even after a 
brief application of current, polypyrrole deposits onto the insulating 
polymer film such that the good mechanical properties of the insulating 
polymer film are retained and the conductivity of the composition 
corresponds to that of pure polypyrrole films. Pyrrole polymers have a 
high temperature resistance, even at temperatures above 250.degree. C. In 
contrast, the mechanical properties of the carrier material employed 
heretofore for electrolytically deposited polypyrroles undergo changes at 
such high temperatures: either the material becomes thermoplastic or it 
beings to decompose at these temperatures. So far polyimides have not been 
used. It has now been found that it is possible to prepare high 
temperature resistant polyimide/polypyrrole compositions with a high glass 
transition temperature. 
Accordingly, the present invention relates to a composition which contains 
polypyrrole and a polyimide said polyimide being soluble in organic 
solvents. 
The soluble polyimides which are suitable for the preparation of the 
compositions of this invention can be divided into the following compound 
classes: 
(A) compounds which are soluble in organic solvents and contain the 
recurring structural unit of formula I 
##STR1## 
wherein the four carbonyl groups are attached direct to separate carbon 
atoms, which carbonyl groups are ortho or peri to one another so that 5- 
or 6-membered imide rings are formed, and Z is a tetravalent organic 
radical which contains at least one aromatic ring, and Z' is a divalent 
aliphatic, cycloaliphatic, aromatic, araliphatic or heterocyclic radical, 
or wherein Z and/or Z' denote combinations of said radicals within the 
given definition; 
(B) compounds which are soluble in organic solvents and contain the 
recurring structural unit of formula II 
##STR2## 
wherein Z' is as defined for formula I, R is a direct C--C bond or is a 
radical selected from: 
##STR3## 
wherein m is 1 if R is --CO--NH-- and is 0 where R is one of the other 
radicals, and * denotes the respective site of attachment to the aromatic 
radical; 
(C) compounds which are soluble in organic solvents and contain the 
recurring structural unit of formula III 
##STR4## 
wherein each of Z" and Q independently of the other has one of the 
meanings given above for Z', and each of X and Y independently of the 
other is --O-- or --NH--. 
In particular, the polyimides of compound class (A) are normally insoluble 
in organic solvents. As generally valid connections between structure and 
solubility of a polyimide cannot at present be established, routine tests 
must be carried out in order to determine whether a specific compound is 
soluble or not and hence can be used as carrier film in this invention. 
A polyimide is usually regarded as soluble if it has a solubility of at 
least 1 mg/l, preferably of at least 1 g/l, at 25.degree. C. in the 
respective solvent. 
Connections between molecular structure and solubility of polyimides are 
described by F. W. Harris and Lynn H. Lanier in "Structure-Solubility 
Relationships in Polyimides", Academic Press, New York, 1977, pp. 183-198. 
The soluble polyimides listed therein can also be employed as carrier 
films within the scope of this invention. 
The tetravalent radical Z can be selected from the following general 
groups: aromatic, aliphatic, cycloaliphatic and heterocyclic groups, 
combinations of aromatic and aliphatic groups and the corresponding 
substituted groups thereof. The groups Z preferably comprise the following 
structures: 
##STR5## 
wherein R.sup.1 is hydrogen or C.sub.1 -C.sub.5 alkyl, and R.sup.2 is 
selected from the group consisting of alkylene of 1 to 3 carbon atoms, 
##STR6## 
where R.sup.3 is hydrogen, C.sub.1 -C.sub.5 alkyl or phenyl. 
The above defined group Z' may preferably be selected from alkylene groups 
of 2 to 12 carbon atoms, cycloalkylene groups of 4 to 6 carbon atoms; a 
xylylene group, arylene groups selected from o-, m- or p-phenylene which 
may carry 1 to 4 C.sub.1 -C.sub.5 alkyl radicals, biphenylene, naphthylene 
or anthrylene; a substituted arylene group of the formula 
##STR7## 
wherein Q.sup.1 is a covalent bond, --CO--, --O--, --S--, --SO--, 
--SO.sub.2 --, --N.dbd.N-- or --NR.sup.1 --, or is a linear or branched 
alkylene group of 1 to 3 carbon atoms, arylene, preferably the phenylene 
group, or is a dialkyl- or diarylsilyl group, and each of R.sup.4 and 
R.sup.5 independently of the other is hydrogen, halogen, preferably 
chlorine or bromine, or alkyl of 1 to 5 carbon atoms, preferably methyl, 
alkoxy of 1 to 5 carbon atoms, preferably methoxy, or is aryl, preferably 
phenyl; or Z' is a radical of the formula IX 
##STR8## 
wherein R.sup.1 has the given meaning and each of R.sup.6, R.sup.7, 
R.sup.8 and R.sup.9 independently is hydrogen, halogen or C.sub.1 -C.sub.5 
alkyl, preferably hydrogen or C.sub.1 -C.sub.5 alkyl. 
R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8 and 
R.sup.9 as C.sub.1 -C.sub.5 alkyl radicals may be methyl, ethyl, n-propyl, 
isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl or neopentyl, with 
methyl being preferred. 
R.sup.4 and R.sup.5 as C.sub.1 -C.sub.5 alkoxy may be methoxy, ethoxy, 
n-propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentoxy or 
neopentoxy, with methoxy being preferred. 
R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8 or R.sup.9 as halogen are 
fluorine, chlorine, bromine or iodine. Bromine and chlorine are preferred, 
with chlorine being most preferred. 
R.sup.4 and R.sup.5 as aryl may be phenyl, or naphthyl which naphthyl can 
be attached in position 1 or 2 to the rest of the system. The preferred 
meaning is phenyl. 
Z' as C.sub.2 -C.sub.12 alkylene is straight chain or branched alkylene, 
e.g. ethylene, trimethylene, tetramethylene, pentamethylene, 
hexamethylene, heptamethylene, octamethylene, nonamethylene, 
decamethylene, undecamethylene, dodecamethylene, as well as 
--C(CH.sub.3).sub.2 --, --(CH.sub.2).sub.3 --C(CH.sub.3).sub.2 
--(CH.sub.2).sub.3 -- or --(CH.sub.2).sub.3 
--CH(CH.sub.3)--(CH.sub.2).sub.4 --. The three last mentioned branched 
alkylene radicals, as well as hexamethylene, are preferred. 
Q.sup.1 as a linear or branched C.sub.1 -C.sub.3 alkylene group may be 
methylene, ethylene, trimethylene, ethylidene or 2-propylidene. Ethylidene 
and 2-propylidene are preferred. 
Z' as a C.sub.4 -C.sub.6 cycloalkylene group may be cyclobutylene, 
cyclopentylene or cyclohexylene. These radicals may be attached in the 
1,2-, 1,3- or 1,4-position to the rest of the molecule. The 1,4-position 
is the preferred position of attachment. 1,4-Cyclohexylene is most 
preferred. 
Z' as xylylene is o-, m- or p-xylylene, but may also be a mixture of these 
radicals. Mixtures of xylylenes or p-xylylene are preferred. 
Where Z' is tolylene, the attachment to the rest of the molecule may be in 
the 2,3-, 2,4-, 2,5-, 2,6-, 3,5-, 3,6-, 4,5- or 4,6-position, with respect 
to the methyl group. 
Where Z' is biphenylene, the attachment to the rest of the molecule may be 
at any position of the biphenylene. Preferred radicals are those in which 
each phenyl nucleus of the biphenylene forms a valence to the rest of the 
molecule. Most preferably, such radicals are the 4,4'-, 3,3'- or 
2,2'-derivatives, first and foremost the 4,4'-derivative. 
Q.sup.1 as arylene may be phenylene or naphthylene, with phenylene being 
preferred. Phenylene shall be understood as meaning here o-, m- or 
p-phenylene, with p-phenylene being preferred. 
Q.sup.1 as dialkylsilyl may be dimethylsilyl, diethylsilyl, 
di-(n-propyl)silyl, di-(isopropyl)silyl or di-(n-butyl)silyl, with 
dimethylsilyl being preferred. 
Q.sup.1 as diarylsilyl is preferably diphenylsilyl. 
The polyimides of the above compound types A, B or C are preferably 
compounds that contain the structural units of formula I, II or III in the 
same sequence. The most preferred polyimides are those consisting 
exclusively of structural units of formula I, II or III, as well as of 
combinations of the different possible structural units of formula I, II 
or III as defined herein. 
The chain length of the polyimides can vary within wide limits. It is 
preferred to use polyimides containing from 5 to 1000 of the recurring 
structural units of formula I, II or III. However, it is most preferred to 
use polyimides containing more than 10, in particular from 10 to 500, of 
the recurring structural units of formula I, II or III. 
It is most preferred to use those polyimides which consist of recurring 
structural units of formula I and are soluble in organic solvents. 
Particularly preferred soluble compounds containing the structural units of 
formula I are those wherein Z is a radical selected from those radicals 
defined hereinbefore as preferred, or is a combination of said radicals, 
wherein R.sup.1 is as defined above, preferably hydrogen or methyl, 
R.sup.2 is --CH.sub.2 --, --CO-- or --C(CH.sub.3).sub.2, and Z' is a 
radical selected from 
##STR9## 
or a combination of said radicals, wherein R.sup.1 and R.sup.6 to R.sup.9 
are as defined above, and Q.sup.2 is --CH.sub.2 --, --CO--, --O--, --S--, 
--SO--, --SO.sub.2 -- or --C(CH.sub.3).sub.2 --. 
Also particularly preferred are polyamides of formula I, wherein Z is a 
radical selected from 
##STR10## 
or is a combination of said radicals, and wherein Z' is a radical selected 
from 
##STR11## 
or is a combination of said radicals, and wherein at least one of R.sup.6 
to R.sup.9 is C.sub.1 -C.sub.5 alkyl, and R.sup.6 to R.sup.9 and Q.sup.2 
have the further meanings as given above. 
A particularly preferred embodiment of this invention comprises the use of 
soluble polyimides containing essentially the recurring structural unit of 
formula I, wherein 
(1) out of the total number of recurring polyimide units 
(A) 0 to 100% of such units have Z equal to a phenylindane radical of the 
structural formula 
##STR12## 
and (B) 0 to 100% of such units have Z' equal to a phenylidane radical of 
the structural formula 
##STR13## 
wherein R.sup.1 and R.sup.6 to R.sup.9 are as defined above, with the 
proviso that 
(2) out of the total number of radicals Z and Z', at least 10% are 
phenylindane radicals. 
Phenylindane polyimides of this type are described in U.S. Pat. No. 
3,856,752. For particulars concerning the preparation and the preferred 
range of these compounds, attention is drawn to the description of that 
patent specification. 
Another preferred polyimide of type (A) contains, as tetravalent radical Z, 
groups of the formula 
##STR14## 
or mixtures of said groups, and, as divalent radical Z', groups of the 
formulae 
##STR15## 
or mixtures of said groups. Out of the total number of radicals Z and Z', 
at least 10% are phenylindane radicals as defined above, R.sup.1 and 
R.sup.6 to R.sup.9 are each independently hydrogen or methyl, R.sup.2 ' is 
hydrogen, halogen or C.sub.1 -C.sub.5 alkyl, preferably hydrogen or 
methyl, and Q.sup.3 is a C--C bond, --CH.sub.2 --, --C(CH.sub.3).sub.2 --, 
--CO--, --O--, --S-- or --SO.sub.2 --. R.sup.15 has the same meaning as 
R.sup.2 '. 
Further preferred polyimides are compounds of formula I containing, as 
structural unit Z', only phenylindane radicals as defined above. 
Polyimides of formula I also meriting attention are those which contain, as 
Z', 10 to 100% phenylindane radicals as defined above, and which contain 0 
to 90% of radicals of the formulae 
##STR16## 
or mixtures thereof, wherein R.sup.2 and R.sup.15 are independently 
hydrogen or C.sub.1 -C.sub.5 alkyl, preferably hydrogen or methyl, but 
most preferably hydrogen. 
Particularly interesting polyimides of formula I are those containing, as 
groups Z, 0 to 100% of the radicals 
##STR17## 
or mixtures of said radicals, and 100 to 0% of the radicals 
##STR18## 
or mixtures thereof, but containing at least 10% of phenylindane radicals, 
based on Z and Z'. 
Further interesting polyimides of formula I are those containing, as Z, 
100% of the radicals 
##STR19## 
or mixture thereof. Especially preferred polyimides of formula I in the 
compositions of this invention are those containing, as Z, 100% of groups 
of the formula 
##STR20## 
or of the formula 
##STR21## 
and containing, as Z', exclusively radicals of the formula 
##STR22## 
or mixture thereof. Finally, polyimides of formula I containing, as groups 
Z, radicals of the formulae 
##STR23## 
or mixture thereof. and, as groups Z', radicals of the formulae 
##STR24## 
or mixture thereof. are also of interest. 
Particularly preferred polyimides of formula I in the compositions of this 
invention are also those wherein Z is 
##STR25## 
and Z' is exclusively 
##STR26## 
Mention is also to be made of polyimides of formula I, wherein Z is 
##STR27## 
or mixture thereof. and Z' is 
##STR28## 
wherein R.sup.2 ', R.sup.15 and Q.sup.3 are as defined above. 
Further polyimides of formula I meriting interest are those wherein Z is 
selected from 
##STR29## 
and Z' is selected from 
##STR30## 
wherein Q.sup.4 is --O--, --S--, --SO.sub.2 --, --CH.sub.2 --, --CO-- or 
--C(CH.sub.3).sub.2 -- and R.sup.2 " is C.sub.1 -C.sub.5 alkoxy, halogen, 
--COOH, --OH or --SO.sub.3 H; and at least 30% of the groups Z are a 
radical of the formula 
##STR31## 
and at least 30% of the groups Z' are radicals of the formulae 
##STR32## 
or mixture thereof; said polyimides having a solubility in phenol of more 
than 10% by weight and 0.5 g/100 ml of said polyimides having an inherent 
viscosity of more than 0.05 in m-cresol (at 30.degree. C.). Polyimides of 
this type are disclosed in U.S. Pat. No. 3,666,709. 
Further interesting polyimides of formula I are those wherein Z is 
##STR33## 
and wherein 10 to 90% of the radicals Z' are 4,4'-diphenylmethane and the 
remaining radicals Z' are 
##STR34## 
or mixture thereof. Compounds of this type, and the preparation and use 
thereof, are disclosed in U.S. Pat. No. 3,708,458. 
Particularly preferred soluble polyimides of formula II (type B) are those 
in which the radical R is in the meta-position to one of the carbonyl 
groups of the imide system. 
Of primary interest are soluble polymers of formula II, wherein R is 
selected from 
##STR35## 
It is also preferred to use compounds of formula II, wherein m is 0. 
If the compounds of formula II contain radicals Z', said radicals are 
preferably the groups specified above, most preferably 
4,4'-diphenylmethane, 4,4'-diphenyl ether or 4,4'-diphenyl sulfone. 
If soluble polyimides of formula III (type C) are used, these are 
preferably compounds wherein Z" is an aromatic radical and Q is an 
alkylene group of 2 to 12 carbon atoms or an arylene group selected from 
o-, m- or p-phenylene or o-, m- or p-tolylene, or an aryl group of the 
formula 
##STR36## 
wherein Q.sup.1 has one of the meanings given above but is preferably 
--O--, --S--, --SO.sub.2 --, --CO--, --CH.sub.2 -- or --C(CH.sub.3).sub.2 
--. 
The radicals Z" and Q may have the same meanings but they can also be 
different. 
X and Y preferably have the same meaning. It is particularly preferred to 
use compounds of formula III, wherein X and Y are --NH--. 
Among the aromatic radicals Z" of compound III, special mention is to be 
made of o-, m- or p-phenylene, as well as tolylene or xylylene and 
4,4'-biphenylene, 2,2'-biphenylene, or radicals of the formula 
##STR37## 
wherein R.sup.4, R.sup.5 and Q.sup.1 have the general and preferred 
meanings as indicated above. 
The polyimides can be prepared by different methods. One method starts from 
the reaction of aromatic tetracarboxylic acids, the carboxyl groups of 
which are always in pairs ortho to each other. These tetracarboxylic acids 
or their dianhydrides are reacted with bifunctional primary amines to 
polyamic acids. These intermediates are normally soluble and may be 
processed to moulded articles. In a second step, the polyamic acid is 
cyclised to form the polyimide. 
Instead of the tetracarboxylic acid, it is also possible to use their 
functional derivatives, for example their chlorides or esters. 
The formation of the amic acid can be carried out in the melt, but 
preferably in a polar solvent such as dimethylformamide, 
dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone or m-cresol. The 
reaction temperature is preferably not allowed to rise above 50.degree. C. 
so as to prevent a premature cyclisation to the polyimide. 
The cyclisation step is preferably carried out in the temperature range 
above 150.degree. C. and, if desired, a dehydrating agent, for example 
acetic anhydride, is added. 
A further method of synthesising polyimides comprises the use of 
tetracarboxylic anhydrides which are reacted with diisocyanates instead of 
diamines. This reaction usually leads direct to the polyimides, with 
elimination of CO.sub.2. However, it is also possible to obtain polyamic 
acids by using tetracarboxylic acids as starting materials. Polyimides of 
type C can be obtained by reacting bismaleimides with primary diamines or 
with diols. Such bismaleimides can also be reacted as bifunctional 
dienophiles, in a Diels-Alder reaction with bisdienes, to give polyimides. 
An outline of the individual methods of preparing polyimides or different 
types of polyimides will be found in Encycl. Chem. Tech., 18, 709-719 
(1982). 
Pyrrole monomers which can be polymerised are pyrrole or substituted 
pyroles which may be C-substituted, N-substituted or both C- and 
N-substituted. These pyrroles must have at least two hydrogen atoms in the 
nucleus (C-bonded) so that the polymerisation can run. 
In particular, the term "pyrrole" shall be understood as meaning homo- or 
copolymers of pyrrole, substituted pyrrole or mixture thereof, or 
copolymers of pyrrole, substituted pyrrole or mixture thereof with 5- or 
6-membered heteroaromatic compounds. 
The pyrrole monomers preferably have the structure of formula X 
##STR38## 
wherein R.sup.16 is hydrogen, alkyl, cycloalkyl, aryl, aralkyl or alkaryl, 
which organic radicals may be substituted by --COR.sup.20, --COOR.sup.20, 
--SO.sub.2 R.sup.20, --SO.sub.3 R.sup.20, --PO.sub.3 R.sup.20 R.sup.21, 
--PO.sub.2 R.sup.20, --NR.sup.20 R.sup.21, --OR.sup.20, --SR.sup.20, --CN 
oder --SiR.sup.22 R.sup.23 R.sup.24, or wherein R.sup.16 is also --CN, 
--SO.sub.2 R.sup.20, --SO.sub.3 R.sup.20, --COR.sup.20, --PO.sub.2 
R.sup.20 or --SiR.sub.3.sup.22, each of R.sup.20 and R.sup.21 
independently of the other is hydrogen, alkyl, aryl or aralkyl, each of 
R.sup.22, R.sup.23 and R.sup.24 independently is alkyl or phenyl, each of 
R.sup.17 and R.sup.18 independently of the other is hydrogen, alkyl, 
cycloalkyl, aryl, aralkyl, alkaryl, --COR.sup.19, --CN or halogen, and 
R.sup.19 is hydrogen, alkyl or aryl. 
R.sup.16, R.sup.17, R.sup.18, R.sup.19, R.sup.20, R.sup.21, R.sup.22, 
R.sup.23 and R.sup.24 as alkyl are preferably C.sub.1 -C.sub.20 alkyl, 
e.g. methyl, ethyl, propyl, butyl, cetyl, lauryl or stearyl, with methyl 
being particularly preferred. 
R.sup.16, R.sup.17 and R.sup.18 as cycloalkyl are preferably C.sub.5 
-C.sub.7 cycloalkyl, e.g. cyclopentyl, cyclohexyl or cycloheptyl, with 
cyclohexyl being most preferred. 
R.sup.17 and R.sup.18 as halogen are fluorine, chlorine, bromine or iodine, 
with bromine or chlorine being preferred. 
Aryl radicals are preferably phenyl or naphthyl, but are most preferably 
phenyl. 
Aralkyl radicals are preferably C.sub.7 -C.sub.14 aralkyl, in particular 
benzyl. 
Alkaryl will preferably be understood as meaning C.sub.7 -C.sub.14 alkaryl 
and is most preferably tolyl or xylyl. 
Substituted radicals are preferably mono- or disubstituted groups, most 
preferably monosubstituted groups. 
Preferred pyrroles are unsubstituted pyrrole, the N-alkylpyrroles, 
preferably N-methylpyrrole, or the N-arylpyrroles, preferably 
N-phenylpyrrole, as well as the pyrroles which are substituted at the 
carbon atoms by one or two alkyl groups or the pyrroles which are 
substituted at the carbon atoms by one or two halogen atoms. 
Among these two last mentioned compound classes, the mono- or dimethyl 
compound or the monobromo or dibromo compound as well as the monochloro or 
dichloro compound is particularly preferred. 
Carbon-substituted pyrroles are preferably substituted in the 3-position, 
4-position or both 3- and 4-positions. 
Within the scope of this invention, pyrrole polymers will be understood as 
meaning quite generally homopolymers as well as copolymers of pyrroles. 
In particular, the homopolymers of unsubstituted pyrrole itself come into 
this category. However, it is also possible to prepare copolymers of the 
above mentioned pyrroles, preferably of unsubstituted pyrrole, with other 
comonomers, preferably with other 5- or 6-membered heteroaromatic 
compounds. Among these heteroaromatic compounds, particularly preferred 
compounds are: furan, thiophene, thiazole, oxazole, thiadiazole, 
imidazole, pyridine, 3,5-dimethylpyridine, pyrazine, pyridazine, 
3,5-dimethylpyrazine, carbazole or phenothiazine. 
Copolymers of this type and the preparation thereof are described e.g. in 
German Offenlegungsschrift No. 3 223 544. 
Particularly preferred copolymers are those of unsubstituted pyrrole and 
unsubstituted or substituted N-methylpyrrole, as well as copolymers of 
unsubstituted pyrrole or N-methylpyrrole and thiophene or furan. 
The preparation of the polypyrrole containing polyimide compositions is 
effected by polymerisation of the pyrrole monomer in the presence of a 
polyimide film. This polymerisation can be carried out by electrolysis, 
but any other polymerisation process can be employed, for example a 
polymerisation using redox pairs. 
Polypyrrole is electrically (electronically) conductive in the charged or 
oxidised state. It is produced in this state by electrochemical 
polymerisation. During the electrochemical polymerisation, a counterion is 
inserted into the material to compensate for the positive charge at the 
polymer backbone. 
However, polypyrrole can also be discharged and converted into a reduced 
(yellow) form, in which state it is an electrical insulating material. 
Within the scope of this invention, the term "polypyrrole" will be 
understood as meaning the oxidised and also the reduced form, but 
preferably the oxidised form. 
The compositions of the present invention are preferably prepared by anodic 
oxidation of a solution of a pyrrole monomer in a polar solvent at an 
electrode which is in contact with the appropriate polyimide film. It is 
most preferred to use electrodes coated with polyimide. The solvent 
contains a conducting salt, the anions of which, as stated above, are 
inserted into the polypyrrole film and result in an increase of 
conductivity. The conducting salt is added in the form of the respective 
protic acid or of a salt thereof, preferably the tetraalkylammonium or 
alkali metal salt, to the electrolyte. 
Accordingly, the invention relates preferably to conductive 
polyimide/polypyrrole compositions containing polypyrrole in the oxidised 
form and, as counterion, an anion selected from the group consisting of 
BF.sub.4.sup.-, PF.sub.6.sup.-, AsF.sub.6.sup.-, SbF.sub.6.sup.-, 
SbCl.sub.6.sup.-, ClO.sub.4.sup.-, IO.sub.4.sup.-, HSO.sub.4.sup.-, 
SO.sub.4.sup.2-, CF.sub.3 SO.sub.3.sup.-, CH.sub.3 C.sub.6 H.sub.4 
SO.sub.3.sup.-, CF.sub.3 COO.sup.-, HC.sub.2 O.sub.4.sup.- or 
[Fe(CN).sub.6 ].sup.3-, as well as from alkyl sulfate, alkyl sulfonate, 
alkyl phosphate or alkylphosphonate, as well as a combination of said 
anions. 
The insertion of counterions and the resultant increase in conductivity is 
known and described e.g. in J. Electrochem. Soc. 128, 2596 (1981). 
Hence the invention also relates to a proces for the preparation of 
polyimide/polypyrrole films by anodic oxidation of a dissolved pyrrole and 
an optional suitable comonomer, at an electrode which is in contact with a 
polymer film, wherein the material employed for the polymer film is a 
polyimide which is soluble in organic solvents. 
The electrolysis is preferably carried out in a polar organic solvent which 
dissolves pyrrole and conducting salt, but not the polyimide film on the 
electrode. Examples of suitable polar organic solvents are alcohols, 
polyols, organic carbonates such as propylene carbonate, ethers such as 
1,2-dimethoxyethane, dioxane, tetrahydrofuran and methyl tetrahydrofuran, 
nitriles such as acetonitrile and benzonitrile, N-methylpyrrolidone, 
methylene chloride, dimethylsulfoxide, dimethylformamide, or acetone. The 
preferred solvent is acetonitrile. 
If water-miscible solvents are employed, small amounts of water to increase 
the electrical conductivity are added, usually in amounts up to 3%, based 
on the organic solvent. Preferred water-miscible solvents are lower 
(C.sub.1 -C.sub.4) alcohols, ethers such as dioxan, tetrahydrofuran or 
1,2-dimethoxyethane, glacial acetic acid, dimethylformide, 
N-methylpyrrolidone, acetonitrile or propylene carbonate. 
It is, however, also possible to use two-phase electrolytic baths, by which 
are meant mixtures of water containing the dissolved pyrrole and the 
optional copolymerisable component, and an organic diluent which is not 
miscible with water. 
Examples of such diluents are organic hydrocarbons such as aliphatic or 
aromatic hydrocarbons as well as halogenated aliphatic or aromatic 
hydrocarbons. Specific examples are hexane, toluene, 1,2-dichloroethane, 
dichloromethane, tetrachloromethane or chlorobenzene. 
The electrolytic cell may contain further auxiliaries which impart the 
desired properties to the compositions of the invention. Examples of such 
substances comprise plasticisers, redox pairs, wetting agents or 
emulsifiers. Regarding such auxiliaries, reference is made to German 
Offenlegungsschrift 3 402 133, in which such electrolytic systems and 
their effect on the properties of the finished polypyrrole films are 
described in detail. The electrolyte contains a solution of the pyrrole 
monomer and the optional comonomer component. 
The amount of this monomer, or of these monomers, in the electrolytic cell 
may vary within a wide range. However, the total amount of dissolved 
monomer must be greater than the concentration required to form the total 
amount of polymer. 
The amount of pyrrole and of the optional comonomer component present in 
the electrolytic solution must be sufficient to ensure a reasonable rate 
of reaction. As a rule, concentrations of more than 10.sup.-3 mole per 
liter are necessary. The saturation concentration of the pyrrole or 
comonomer in the respective electrolyte shall be ragarded as the upper 
limit of the monomer concentration. It is preferred to use 0.01 mole per 
liter to 0.1 mole per liter of dissolved pyrrole. 
The concentration of conducting salt is preferably 0.001 to 1 mole per 
liter. But here too it is possible to employ a concentration up to 
saturation point of the electrolyte. 
In carrying out the process of this invention, particular regard is to be 
had to the electrodes. Electrodes which are coated with the respective 
polyimide are employed. Useful electrode materials are conventional 
conductive materials, for example metals such as nickel or steel, which 
can be used for the polypyrrole synthesis. It is preferred to use 
graphite, steel or noble metals, especially platinum. However, it is also 
possible to use electrodes which are made from electrically conductive 
polymers, for example from polypyrrole or polythiophene formed by anodic 
oxidation, or from doped p-conductive polyphenylene. 
The electrolytes may have any shape. Plate-shaped electrodes arranged in 
parallel may be used, or else cylindrical electrodes which can be rotated 
about their longitudinal axis. 
The coating of the electrodes can be effected in a variety of different 
ways, for example by spin or curtain coating. Depending on the shape and 
material of the electrode, different requirements must be made of the 
coating procedure and of the electrode material as substrate. 
A generally applicable, and therefore preferred, process comprises using a 
polyimide solution, applying said solution to the surface of the electrode 
and allowing the solvent to evaporate or removing the solvent by applying 
a vacuum, to leave a polyimide film. The thickness of this film can be 
controlled via the concentration or the amount of the solution employed. 
It is preferred to use solutions of polyimides with a viscosity that is 
greater than 1%, most preferably greater than 5%, than that of the pure 
solvent. 
Typical examples of organic solvents for soluble polyimides are: 
N,N-dimethylformamide, N,N-diemthylacetamide, N-methyl-2-pyrrolidone, 
N,N-diethylformamide, N,N-diethylacetamide, N-methylcaprolactam, dioxane, 
dimethylsulfoxide, tetramethylurea, pyridine, dimethylsulfone, 
hexamethylphosphoramide, tetramethylenesulfone, formamide, 
N-methylformamide, .gamma.-butyrolactone, tetrahydrofuran, m-cresol, 
phenol, 2-methoxyethyl acetate, 1,2-dimethoxyethane, bis(2-methoxyethyl) 
ether, chloroform, and nitrobenzene. 
The solvent may be used alone or in combination with diluents such as 
benzene, benzonitrile, xylene, toluene and cyclohexane. 
However, there are also polyimides which are even soluble in solvents of 
low dissolving power. Examples of such solvents are aliphatic ketones such 
as cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, 
4-methylcyclohexanone, 3-methylcyclohexanone or 2-methylcyclohexanone; 
aromatic-aliphatic ketones such as acetophenone, propiophenone or 
butyrophenone; chlorinated hydrocarbons such as methylene chloride, 
chloroform, tetrachloroethylene, chlorobenzene or o-dichlorobenzene; 
ethers such as ethylene glycol dimethyl ether, diethylene glycol dimethyl 
ether, tetrahydrofuran or dioxan; ether acetals such as methyl glycol 
acetate or ethyl glycol acetate; as well as other polar aprotic solvents 
such as propylene carbonate or isophorone, which have a somewhat weaker 
dissolving power than the strongly dissolving polar aprotic solvents such 
as N-methypyrrolidone, .gamma.-butyrolactone or N,N-dimethylacetamide. 
The thickness of the polyimide films to be applied to the electrode is 
preferably not more than 50 .mu.m, but most preferably less than 10 .mu.m. 
The electrolysis is preferably carried out with a simple electrolytic 
device comprising a cell without diaphragms and two electrodes, preferably 
steel or platinum electrodes. At least the anode onto which the pyrrole 
later deposits must be flat and coated with a polyimide film. 
Other electrolytic devices, for example cells with diaphragms or those with 
reference electrodes for exact determination of the potential, may also be 
used. It is expedient to measure the charge (ampere* sec) to determine the 
amount of deposited polypyrrole. 
The electrolytic solution can be agitated during the electrochemical 
polymerisation of monomers. Agitation can be effected by any of the 
customary means, for example by vigorous stirring with paddle stirrers, 
magnetic stirrers, ultrasonics, vibration or by passing gases through the 
electrolytes (including the gases produced at the cathodes). Stirring can 
also be effected by agitating the electrodes. The electrochemical 
polymerisation can be carried out by applying a voltage to the electrodes. 
This voltage is chosen such that it suffices to carry out the reaction and 
it may be a direct current voltage or an alternating current voltage on 
which a direct current component is superimposed. Alternating current 
voltages may have widely different time gradients: for example, sinusoidal 
or rectangular gradients. It is preferred to use direct current voltages. 
The voltage between the electrodes should be sufficient to oxidise the 
monomers without producing appreciable changes in the cell, for example by 
degradation of components in the cell. 
In general, current densities of up to 2 A/cm.sup.2 are applied, preferably 
however current densities of less than 500 mA/cm.sup.2. 
The electrolysis can also be carried out under an inert gas, as well as in 
air. 
In the electrolysis, the pyrrole monomer is oxidised at the anode. It is 
expedient to keep the temperature of the electrolyte in the range from 
-20.degree. to +30.degree. C. during the electrolysis. However, the 
temperatures may deviate from the indicated range. The temperature limits 
depend primarily on the electrolytic solution (solidification or 
evaporation point). The electrolysis is preferably carried out at room 
temperature. 
The amount of pyrrole deposited onto the polyimide film will depend 
entirely on the intended end use of the films and can be rapidly 
determined by the skilled person by means of routine tests. 
The pyrrole films deposited anodically during the electrolysis in the 
presence of conducting salts are conveniently washed with solvent to 
remove conducting salt adhering thereto, and dried at .gtoreq.50.degree. 
C. After it has been dried, the polyimide/polypyrrole film can be easily 
peeled from the electrode. 
The compositions of the invention can be used for making free-standing 
electrically conductive films with a high glass transition temperature and 
excellent tear strength. Such films can be used in the field of 
electronics and micro-electronics, for example as conductive composites in 
the fabrication of electric conductors, electrodes, batteries, switches or 
semi-conductors, as well as in antistatic finishing or in the 
electromagnetic screening of electronic components. 
The films of the present invention thus combine high electrical 
conductivity, high mechanical stability, high thermal resistance (T.sub.g 
&gt;250.degree. C.) and chemical resistance.

EXAMPLES 
General working directions: 
A glass vessel is charged with 250 ml of electrolytic solution (0.1 mole/l 
of conducting salt, 0.05 mole/l of pyrrole (derivative) and optional 
comonomer, and acetonitrile as solvent, with 1% water content). Two 
electrodes (50.times.20.times.1 mm), the anode of which is coated on the 
surface with a polyimide film.sup.(1), are put into the solution and 
spaced 4 cm apart. With stirring and while blanketing with argon, 
electrolysis is carried out for 5, 10 or 30 minutes. The formation of a 
polymer composite of the polyimide and polypyrrole rapidly causes the 
anode to turn dark green to black. After rinsing the anode with 
acetonitrile and drying it at 60.degree. C., the polyimide/polypyrrole 
film can be removed from the substrate. The glass transition temperature 
(T.sub.g) of the composite film corresponds to that of the pure polyimide 
film. 
FNT .sup.(1) Coating is effected by spin coating. 
Examples 1-6 
Polyimide/polypyrrole films are prepared in accordance with the general 
directions above. The polyimide employed is in each case DAPI 
polyimide.sup.(2). The pyrrole monomers, the conducting salt and some 
properties of the composite film will be found in Table Ia. Parameters 
which are varied during the film formation are listed in Table Ib. All 
composite films can be folded and creased without tearing, whereas the 
corresponding pure polypyrrole films tear. 
FNT .sup.(2) DAPI polyimide contains the following structural unit: 
TABLE 1a 
__________________________________________________________________________ 
##STR39## 
Electrical conductivity 
Monomer (mixture) for Conducting of the composite 
T.sub.g of the 
composite 
Example 
making the polypyrrole film 
salt (S/cm) film 
__________________________________________________________________________ 
(.degree.C.) 
##STR40## (C.sub.4 H.sub.9 ).sub.4 N.sup..sym. BF.sub.4. 
sup..crclbar. 
0.5-10 320 
2 
##STR41## (C.sub.4 H.sub.9).sub.4 N.sup..sym. PF.sub.6.s 
up..crclbar. 
15-18 320 
3 
##STR42## (C.sub.4 H.sub.9).sub.4 N.sup..sym. ClO.sub.4. 
sup..crclbar. 
3-4 320 
4 
##STR43## (C.sub.4 H.sub.9).sub.4 N.sup..sym. BF.sub.4.s 
up..crclbar. 
1 .times. 10.sup.-4 
320 
5 
##STR44## (C.sub.4 H.sub.9).sub.4 N.sup..sym. BF.sub.4.s 
up..crclbar. 
1 .times. 10.sup.-5 
320 
6 
##STR45## (C.sub.4 H.sub.9).sub.4 N.sup..sym. CH.sub.3C. 
sub.6 H.sub.4SO.sub.3.sup..crclbar. 
2 .times. 10.sup.-4 
320 
__________________________________________________________________________ 
TABLE Ib 
______________________________________ 
Current Thickness 
Duration of the 
Electrode density of the PI 
electrolysis 
Example 
material (mA/cm.sup.2) 
film (.mu.m) 
(min) 
______________________________________ 
1 Pt 1,7 5 5 
2 Pt 1,2-1,4 2.5 10 
3 Pt 1,2-2,2 2.5 10 
4 Inox.sup.(1) 
0,9 5 10 
5 Pt 1,4-1,8 5 10 
6 Inox.sup.(1) 
0,3-0,7 5 30 
______________________________________ 
.sup.(1) stainless steel 
Examples 7-9 
The procedure of of Example 1 is repeated, only other polyimide films are 
used for coating the electrode. The components of the film, as well as 
some of their properties, are indicated in Table IIa, and the conditions 
for the preparation of the films are set forth in Table IIb. All composite 
films can be folded and creased without tearing, whereas corresponding 
polypyrrole films tear. 
TABLE IIa 
__________________________________________________________________________ 
Electrical con- 
ductivity of 
T.sub.g of the 
Pyrrole 
Conducting 
composite 
composite 
Ex. Polyimide component monomer 
salt (S/cm) film 
__________________________________________________________________________ 
(.degree.C.) 
##STR46## 
##STR47## 
(C.sub.4 H.sub.9).sub.4 N.sup..sym. 
BF.sub.4.sup..crclbar. 
3 .times. 10.sup.-1 
280 
##STR48## 
8 
##STR49## 
##STR50## 
(C.sub.4 H.sub.9).sub.4 N.sup..sym. 
CH.sub.3C.sub.6 H.sub.4SO.sup..crc 
lbar. 7 .times. 10.sup.-4 
280 
##STR51## 
9 
##STR52## 
##STR53## 
(C.sub.4 H.sub.9).sub.4 N.sup..sym. 
BF.sub.4.sup..crclbar. 
1 .times. 10.sup.-1 
300 
##STR54## 
__________________________________________________________________________ 
TABLE IIb: 
______________________________________ 
Current Thickness 
Duration of 
Electrode density of the PI 
electrolysis 
Example 
material (mA/cm.sup.2) 
film (.mu.m) 
(min) 
______________________________________ 
7 Pt 2.0-2.1 5 10 
8 Pt 0.5-1.7 5 10 
9 Pt 1.8-2.2 5 10 
______________________________________