Electropolymerization mechanism of highly conductive polyanilines and the unit molecular structure determined from a coulometric analysis of the electropolymerization

Aniline and several aniline derivatives were electropolymerized with two different electrolysis modes: potential-sweep electrolysis and constant-current electrolysis. The voltammetric and chronopotentiometric responses during electropolymerization led to two polymerization mechanisms: radical-coupling polymerization and incorporation-oxidation polymerization. The latter polymerization proceeds as follows: 1 During the initial stage a seed polymer with a low molecular weight is electrodeposited on the electrode surface. 2 The seed polymer is electro-oxidized and cation radicals are generated in the seed polymer. 3 The cation radicals oxidize dissolved monomers and incorporate the oxidized monomers. This polymerization was found to give highly conductive polyanilines. On the basis of the fact that the incorporation-oxidation polymerization obeyed Faraday's law, the electron number of the polymerization reaction of aniline was analyzed coulometrically. The determined number implied that the polymeric backbone consisted mainly of benzenoid structures, and that 2.77 anions were doped per an aniline unit.