EFFECT OF COUNTER IONS IN ELECTROCHEMICAL POLYMERIZATION MEDIA ON THESTRUCTURE AND RESPONSES OF THE PRODUCT POLYANILINE FILMS - III - STRUCTURE AND PROPERTIES OF POLYANILINE FILMS PREPARED VIA ELECTROCHEMICALPOLYMERIZATION

Using polymerization solutions containing 0.1 M aniline and 1 M HCl or 1 M HClO4, which happened to give the same pH (0.2), we investigated the effects of different counter-anions on the primary and higher orde r structures as well as on electrochemical responses of the obtained p olyaniline (PAn) films. From time developments of polymerization curre nt and u.v.-visible absorption spectra as well as the results of atomi c force microscopic (AFM) observation, we found that in both media the higher order structure of the PAn films developed in almost the same manner from grainy to fibrillar texture and finally to bundles of the fibrils. The primary structures as judged from the spectra were not ve ry different, but the structural size was somewhat larger for the film s prepared in HClO4 than the ones prepared in HCl. The apparent acid d issociation constants of the resulting PAn films were again not so dif ferent, reflecting little differences in their primary structures. How ever, the electrochemical responses of the former were much slower tha n those of the latter, especially when the transition from the oxidati on to reduction form was compared, reflecting differences especially i n the structural size and compactness of their higher order structures . (C) 1998 Elsevier Science Ltd. All rights reserved.