Comparative study of anion-involvement in redox transformations of poly(o-phenylene-diamine) (PPD) films by a coupled electrochemical and radiometric technique

The sorption of H2PO4-, HSO4- and Cl- ions in poly(o-phenylene-diamine) (PPD) film was studied and compared by the radiotracer technique using S-35, P-32 and Cl-36 isotopes for labelling. It was found that the anion sorption in both oxidized and reduced films depends on pH, i.e. on the protonation of the film; however, the protonation and anion sorption is not an essential condition for the occurrence of the redox process. Results furnished by differential volt-radiometric measurements advocate in the favour of the assumption that the reduction of film results in the formation of three or four types of centre with different behaviour with respect to the protonation and anion sorption. It was demonstrated that PPD films are very selective for the sorption of HSO4-(SO42-) ions in the presence of a great excess of other anions.