INVESTIGATION OF ION AND SOLVENT TRANSPORT ACCOMPANYING REDOX REACTIONS OF POLYVINYLFERROCENE FILMS USING AN IN SITU ELECTROCHEMICAL QUARTZ CRYSTAL MICROBALANCE TECHNIQUE

The in situ electrochemical quartz crystal microbalance (in situ EQCM) technique has been applied to study ion and solvent transport accompanying the redox reaction of polyvinylferrocene (PVF) film coated on quartz crystal electrodes in aqueous and acetonitrile media. The dependence of apparent formal potentials (E(f)poly)app of the F(c)-degrees/F(c)+ redox couple (F(c)-degrees and F(c)+ represent the reduced and oxidized sites, respectively, in the PVF film) upon the concentration of supporting electrolyte has been also examined in comparison with those of solution-phase ferrocene derivatives. The PVF film is ideally permselective to ClO4- anion in both aqueous and acetonitrile media. The PVF oxidation (or reduction of polyvinylferricenium ion) in aqueous media is accompanied by the ingress (or egress) of one ClO4- ion per redox site and some solvent (ca. one H2O per redox site). In LiClO4 acetonitrile media, during the oxidation process ClO4- ion with some solvent inserts into the film and the reverse phenomenon occurs during the reduction process. The results demonstrate that a combination of the in situ EQCM measurement and the measurement of the dependence of (E(f)poly)app on the concentration of supporting electrolyte makes possible to elucidate quantitatively the ion and/or solvent transport process across the polymer film/solution interface during the redox reaction.