Poly(o-phenylenediamine)-film-coated electrode: incorporation of o-benzoquinone and permselectivity of I– and Br–

A poly(o-phenylenediamine)(PoPD) film has an electroinactive potential range where the film itself is not redox active. Even within the range, the redox waves of I– and Br– were evident, while those of Fe2+, TI+ and Mn2+ were not observed. The respective Levich plots obtained from the voltammograms for the oxidation of I– and Br– showed that the film was permeable to I– and Br–. Thus, the film showed permselectivity of I– and Br–. The film also responded to several dihydroxybenzenes such as catechol in spite of its electroinactivity. In particular, the noteworthy behaviour in those responses was the following: (1) cathodic currents of benzoquinones, the products of oxidation of dihydroxybenzenes, were remarkably suppressed and (2) the anodic currents of dihydroxybenzenes as well as the redox currents of the film itself gradually decreased with repeated potential scans. Catechol was selected as being representative of dihydroxybenzenes and the mechanism of the behaviour was studied. Voltammetric and spectroscopic results regarding the effect of incorporation of o-benzoquinone in the film were obtained. The amount of o-benzoquinone incorporated was changed by the number of the potential cycles (N). The amount of I– and Br– permeating was, therefore, controllable by altering N. Furthermore, the permselectivity of I– and Br– was enhanced by enlarging N.