The effect of film thickness and growth method on polyaniline film properties

The properties of polyaniline (PANI) films, grown electrochemically on Au u sing the potential sweep method to two different upper potential limits (ty pe I and II) to various thicknesses in sulfuric acid solution, were studied systematically using cyclic voltammetry. ne impedance, and for the first t ime, by tracking die rate of the hydrogen evolution reaction (HER). The HER results show that hath films follow the nucleation and growth mechanism in itially and that continuing growth occurs primarily at the outer PANI surfa ce. Because type II PANI films are formed at a much more rapid rate than ty pe I films, a greater amount of anodic degradation products are incorporate d into type I films. Impedance and HER measurements show that type II films , compared for the first time in this work with type I films, have a more o pen PANI film/Au interfacial structure. A new observation is that the cycli c voltammograms for type I films show a prepeak which is absent for type II films, Furthermore, constant PANI redox peak potentials are observed for t ype I films, whereas these shift with film thickness for type II films. Thi s unique observation implies that type II films undergo structural changes during their growth, while type I films remain more uniform. (C) 1999 The E lectrochemical Society. S0013-4651(98)12-003-7. All rights reserved.