CHARGE-TRANSFER REACTIONS ON ELECTRODES COVERED WITH BILAYERS OF CONDUCTING POLYMERS

Bilayers formed by combinations of conducting polymers, polypyrrole (P Py) or poly(N-methylpyrrole) (PMPy), as anion exchangers, and the abov e materials with immobilized poly(4-styrenesulphonate) anions as catio n-exchanging matrices, PPy(PSS) or PMPy(PSS), were studied on glassy c arbon electrodes using cyclic voltammetry. The electrochemical respons e is dependent on the formal potentials of the constituent polymers an d the permeability of the outer matrix to charge-compensating ions. On the basis of electrochemical measurements and EDAX spectroscopy, for PPy(PSS)(inner)/PMPy(outer) and PMPy(PSS)/PMPy bilayers, the inner fil m was found to be permanently oxidized, independently of the electrode potential. This was caused by impermeability of the outer layer to ca tions accompanying the charge/discharge processes of the inner polymer . Charge-transfer reactions of redox electrolytes were studied on rota ting disk electrodes covered with polymer bilayers. It was demonstrate d that the reaction rate may be controlled by a slow charge transfer b etween both polymer films (for the Eu3+/Eu2+ couple) and by the Donnan potential prevailing at the outer polymer\electrolyte solution interf ace (for the Fe(CN63-/4- couple).