Electrochemical and ion exchange properties of polyaniline-poly(vinylsulfonate) composites in aqueous and nonaqueous media

A composite of polyaniline and poly(vinylsulfonate) was obtained by electrochemical polymerization of aniline in a solution containing poly(vinylsulfonate) ions. The irreversible retention of the polyelectrolyte was confirmed using Fourier transform infrared reflection-absorption spectroscopy: The symmetric stretching of the -SO3- group is observed at ca. 1040 cm(-1), in addition to the bands due to polyaniline. The polyelectrolyte is retained even after extensive cycling in acidic aqueous or neutral nonaqueous solutions not containing polyelectrolyte. The composite film is electroactive in aqueous (pH < 7) and nonaqueous media. The specific charge in aqueous media is ca. 84 (+/-2) Ah/kg, as measured using an electrochemical quartz crystal microbalance (EQCM) (both redox processes). The ion exchange of the modified electrode was studied using probe beam deflection and EQCM. The charge compensation in aqueous solution involves a mixed proton and anion exchange. Three different regimes are observed at different pH values. At pH below -1 and pH above 2, the dominant process of charge compensation is proton exchange. At intermediate pH values (between -1 and 2), there is an increased contribution of anion insertion to the charge-compensation process. In nonaqueous media, it seems that cations are retained inside the film and the charge is compensated only by anion exchange.