Influence of the doping anion concentration on the mechanism of redox reactions of polyaniline

Cyclic voltammetry was used to characterize polyaniline obtained in the electropolymerization process in hydrochloric acid on Pt and GC electrodes. In order to determine the influence of the doping anion concentration on the redox properties of polyaniline, the polymer films were investigated in solutions containing Keggin-type heteropolyacids and various amounts of HCl. Although heteropolyanions, because of their large size, do not diffuse into the polymer matrix, polyaniline remains electroactive in their presence due to surface reactions. Significant changes in the redox properties of polyaniline were observed while increasing the concentration of small anions capable of doping the polymer. Detailed analysis of the results can help to study the doping mechanism thoroughly.