CHARGE-TRANSPORT PROCESSES IN ELECTROCHEMICALLY DEPOSITED POLY(PYRROLE) AND POLY(N-METHYLPYRROLE) THIN-FILMS

Poly(pyrrole) (pPy) and poly(N-methylpyrrole) (pNMePy) films that were electrodeposited under similar conditions were compared in terms of e lectronic conductivities and counterion diffusion coefficients, Films were prepared and compared both in aqueous electrolyte (Cl-, ClO4- cou nterions) and in non-aqueous (propylene carbonate) electrolyte (ClO4- counterion). Consistent with the range of values reported in the liter ature, the electronic conductivities differed by a factor of ca, 5x10( 3), although this is lower than the often-cited value of 10(5). This s maller difference in the conductivities is more consistent with that e xpected on the basis of simple steric factors. A.c. impedance measurem ents were used to determine the counterion diffusion coefficients. Tha t for ClO4- was approximately one order of magnitude lower in pNMePy t han that in pPy, possibly due either to differences in morphology or t o stronger interactions of the counterion with the polymer chains.