ELECTROCHEMICAL QUARTZ-CRYSTAL MICROBALANCE STUDY OF POLYPYRROLE AND TUNGSTATE POLYANION COMPOSITE FILMS

A composite film comprising polypyrrole (PPy) and isopoly tungstate (PW) anion was prepared by electropolymerization of pyrrole in an aqueous solution of polytungstic acid. The formation of the PPB-PW film was traced using an electrochemical quartz crystal microbalance (EQCM). The oxidation-reduction behavior of the film was also investigated by the EQCM and compared with that of PPy film prepared in acidic KCl solution. From the EQCM measurements, the growth rate of the PPy-PW film under constant current oxidation at 0.186 mA cm(-2) was evaluated as 0.97 mu g mC(-1), which was 2.8 times as high as that of PPy-Cl film prepared in acidic KCl solution. From emission spectroscopic analysis, the composite PPy-PW film was found to contain 51 wt.% tungsten, or 67 wt.% meta-polytungstate anion, H2W12O406-. The PPy-PW film behaved like a redox polymer film in which the W(V)/W(VI) couple of the doped polytungstate anion functions as a reversible redox center. The doped PW changes the ionic permeating property of the polymer film; the PPy-PW film reveals protonic permeability, although the ordinary chloride ion doped PPy has anionic permeability.