Microgravimetric and laser beam deflection studies of redox reactions in polyaniline at various concentrations of doping anions

Quartz crystal microbalance and laser beam deflection techniques were used to study the role of ion exchange in electrochemical oxidation and reduction of polyaniline films synthesized in various acids. Mass changes and beam deflection angles were measured during voltammetric cycling of polyaniline in aqueous solutions containing H₄SiW₁₂O₄₀ and various amounts of HCl or HClO₄. The obtained results confirm the initial hypothesis that due to their large size heteropolyanions cannot dope the bulk of the polymer. An increase in the doping anion concentration leads to significant changes of mass and a deflection angle associated with redox reactions in polyaniline. Doping anions as well as protons are exchanged between the polymer and the supporting electrolyte. The contribution of protons and anions depends not only on the concentration but also on the conditions under which the film was synthesized.