The charge potential relationship in polyconjiugated conducting polymers. Determination of E0 and n values for polypyrrole and polythiophene.

Experimental charge--voltage relationships for reversible oxidation of polypyrrole (PP) and polythiophene (PT) in acetonitrile were obtained. Curve-fitting analysis according to Feldberg's model for mixed faradaic and capacitive contributions provides the E0 and n-values of these materials. PP shows a single process at E0 = -0.66 V (vs ag/Ag+) with n = 0.6, while PT shows two isoelectronic processes at E0 = 0.28 and 0.58 V with n = 0.3. The single process for PP is due to merging of two one-electron processes involving polaron and bipolaron species. PT is suggested to be involved in 0.5-electron steps possibly due to dimeric associations in the polymer chain.