Influence of inorganic and organic supporting electrolytes on the electrochemical synthesis of polyaniline, poly(o-toluidine) and their copolymer thin films

The influence of inorganic and organic supporting electrolytes on electrochemical, optical and conducting properties of polyaniline (PA), poly(o-toluidine) (POT) and poly(aniline-co-o-toluidine) (PA-POT) thin films have been investigated. The films were synthesized electrochemically individually and then combinedly as copolymer under cyclic voltammetric conditions in aqueous solutions of inorganic acids viz. H2SO4, HCl, HNO3, H3PO4 and HClO4 and organic acids viz. benzoic acid, cinnamic acid, oxalic acid, malonic acid, succinic acid and adipic acid at room temperature. The electrosynthesized films were characterized by cyclic voltammetry, UV-visible spectroscopy and conductivity measurement using four-probe technique. It was observed that the current densities are strongly influenced by the size and the nature of the anion present in the electrolyte. The optical absorption spectra indicate the formation of the conducting emeraldine salt (ES) phase irrespective of the inorganic electrolytes, whereas it shows dependence on organic acid supporting electrolytes. Among organic acids, the formation of thin films by cyclic voltammetry and the conducting ES phase was observed only in the case of oxalic acid. It was also found that the conductivity of thin films is greatly affected by the nature and size of the anion present in the electrolyte. (C) 2002 Elsevier Science B.V All rights reserved.