DIRECT INSITU EVIDENCE FOR PROTON ANION-EXCHANGE IN POLYANILINE FILMS BY MEANS OF PROBE BEAM DEFLECTION

Probe beam deflection (PBD) was used to monitor the ion exchange between polymer film and bulk electrolyte during the redox reaction in polyaniline in aqueous electrolyte (HCl, HClO4, H2SO4). The PBD results clearly show that protons as well as anions are exchanged during the first oxidation process. Protons are exchanged at potentials below 0.55 V(rhe). The relative contribution of the proton to the overall process depends not only on the pH of the electrolyte but also on the nature of the specific anion present. While the participation of H+ could be observed in HCl for a concentration of 0.5M a concentration of 1M was needed in H2SO4. A simple model based on the protonation equilibria of leucomeraldine species is used to analyze the results quantitatively. The results are discussed in terms of previously proposed mechanisms of redox processes in polyaniline.