POTENTIAL PROFILE ACROSS A CONDUCTING POLYMER FILM DURING MEDIATED ELECTROLYSIS

Rotating disk voltammetry of ferrocene oxidation at electrodes coated with poly[l-methyl-3-(pyrrol-1-ylmethyl)pyridinium]+ films of varying thickness has been used to obtain potential profiles across the polymer. The potential of the polymer increases logarithmically with distance from the polymer/solution interface, with a slope of ca. 90 mV/decade. This nonlinear relationship clearly indicates that the polymer does not behave like a metallic conductor. Instead, electron transport is driven by a linear concentration gradient of charge carriers (oxidized sites) as in a polymer with discreet redox sites. Knowledge of the potential profile across the polymer allows calculation of in situ conductivity as a function of potential. Results are in good agreement with values determined by dual electrode voltammetry.