MIXED IONIC-ELECTRONIC CONDUCTION OF A CONDUCTING POLYMER FILM - AC-IMPEDANCE STUDY OF POLYPYRROLE

Polypyrrole (PPy) films were studied by ac impedance spectroscopy both in a free-standing membrane and in a modified electrode arrangement. The experimental results were analyzed by comparison with previously d erived kinetic models, allowing to obtain, through a non-linear least- squares fitting procedure, both transport (diffusion coefficients and concentration of ion- and electron-exchanging sites) and interfacial p arameters (charge transfer resistances and double layer capacitances). PPy film thickness, nature and concentration of the electrolytes and duration of the immersion were varied in a systematic way. The transpo rt properties were found to depend on both anions and cations containe d in the electrolyte and to be independent of polymer film thickness.