FORMATION AND ELECTROCHEMISTRY OF POLYANILINE IN AMBIENT-TEMPERATURE MOLTEN-SALTS

Polyaniline (PAn) can be prepared on platinum and glassy carbon electrodes by anodic oxidation of the monomer in ambient-temperature molten salts, consisting of mixtures of aluminum chloride and 1-methyl-3-ethyl-imidazolium chloride. The formation and electrochemistry of PAn vary as the melt's composition is changed from 0.8:1 (basic) to 2:1 (acidic). The oxidation mechanism of aniline in melts differs from that in acidic aqueous solution and protons are not involved in the polymerization process. The peak potentials of PAn films in aniline-free melts shift to more positive potentials with increasing melt acidity. Transfer of PAn films between different melts and aqueous solution are reversible. Comparison of PAn cyclic voltammograms in aqueous solution with that in the melt suggests that crosslinking and multiple substitution of the benzene ring probably take place during the propagation process and deterioration in aniline-free melts.