Electropolymerized poly(2-vinylpyridine) coatings as ion-exchange polymer modified electrodes

The effects of pH and of the nature and concentration of the electrolyte on the electrochemical behaviour of the Fe(CN)(6)(3-/4-) charge-transfer reac tion at a poly(2-vinylpyridine)-coated electrode formed by electropolymeriz ation have been studied. Cyclic voltammetry during the Fe(CN)(6)(3-) incorp oration process was combined with measurement of the saturated concentratio n of the Fe(CN)(6)(3-) confined in the films to investigate the electrochem ical behaviour and the fundamental nature of the ion-exchange polymers. The poly(2-vinylpyridine) films formed by electropolymerization were found to have better properties (i.e., larger amount of Fe(CN)(6)(3-) can be incorpo rated at various pH values and films are more chemically stable under acidi c conditions) as polymer-modified electrodes than those formed by solvent e vaporation. Of the various anions studied, ClO4- was found to be distinct f rom the others (Cl-, NO3-, Br- and SO42-). On the one hand, the polymer fil ms exposed to ClO4- are more dense and rigid than those exposed to other an ions and show relatively little electroactivity. On the other hand, when th e films are exposed to increasing concentrations of Cl-, the films become m ore swollen, thereby reducing the resistance within the film and enhancing the rate of charge-transfer from the outer film surface to the electrode su rface.