The electrochemical formation and properties of bilayers composed of polypyrrole and C60Pd films

Bilayers composed of the redox-active polymers, polypyrrole (a p-doped system) and C60Pd (an n-doped system), were prepared by sequential electropolymerization of parent monomers. The C60Pd film was formed under cathodic polarization in the potential range for reduction of palladium(II) acetate and C-60. Polypyrrole was obtained by electro-oxidation of parent monomer. The electrochemical properties of the electrode/polypyrrole/C60Pd and electrode/C60Pd/polypyrrole bilayers, which are redox active over an unusually broad potential range, have been analyzed by cyclic voltammetry, and the morphology of these films has been investigated by scanning electron microscopy. In the case of the electrode/polypyrrole/C60Pd bilayer, the high permeability of C60Pd film for the supporting electrolyte ions allows the oxidation of the polypyrrole inner layer. A strong solvent effect was observed for the voltammetric response of inner polypyrrole layer. The charging processes of outer C60Pd layer do not significantly depend on the solvent. In the case of the electrode/C60Pd/polypyrrole bilayer, the outer polypyrrole layer inhibits the reduction of the inner C60Pd layer. The low permeability of this polypyrrole film for supporting electrolyte cations is responsible for such a behavior.