Comparison of Impedance Responses of Poly (o-aminophenol) Film Electrodes in the Presence of Sulfate and Benzenesulfonate Anions. Application of a Transmission Line Model

A transmission line model was employed to interpret the impedance response of pol(o-aminophenol) (POAP) film electrodes in contact with sulfate and benzenesulfonate (BS) solutions. These two different anions were chosen due to their different characteristics of size and electron distribution, which assures a different interaction with the redox centers of the polymer. Electron (De) and ion (Di) diffusion coefficient values were separately obtained. Both diffusion constants depend on the type of anion present in the electrolyte solution. The effect of sulfate and BS anions on the electron conduction of poly(o-aminophenol) was explained in terms of their abilities to reduce repulsive interactions between redox sites of the polymer. In this regard, sulfate anions seem to be more effective than BS ones to attenuate repulsive interactions between redox centers of POAP. Also, both parameters depend on the electrolyte concentration and film thickness. These effects were attributed to incorporation of electrolyte into the porous structure of POAP. The increase of the ion conduction of POAP with the incorporation of electrolyte was attributed to a contribution of the counterions, contained in the inner electrolyte, to the charge transport process.