INVESTIGATION OF DYNAMICS OF FARADAIC PROCESSES IN POLYPYRROLE FILMS BY ELECTROCHEMICAL IMPEDANCE AND COLOR ADMITTANCE SPECTROSCOPIES

Dynamics of faradaic processes in polypyrrole (PPY) films depending on the thickness of the films and on applied dc potentials have been investigated by ac electromodulation spectroscopy techniques. The comparison of the capacitance plots derived from the impedance plots with the modulated transmittance (color admittance, DELTAT/DELTAE) plots revealed whether the overall electrical responses were due to faradaic processes in the PPy films or not. The results showed that the faradaic processes in both the thicker (0.26 mum) and the thinner (ca. 0.03 mum) PPy films in their highly oxidized state were represented by a single relaxation process, and that those in the thicker films in their intermediately oxidized state were clearly resolved into two processes, the faster and the slower processes. The differences in mechanisms of the faradaic processes between the thicker and the thinner films depending on the dc potentials are discussed by using an electrical equivalent circuit.