THE INFLUENCE OF WATER ON THE ELECTROCHEMICAL ACTIVITY OF POLY(N-VINYLCARBAZOLE) FILMS

Poly(N-vinylcarbazole) (PVCz) films were prepared by potentiostatic deposition onto gold, platinum and indium tin oxide (ITO) electrodes from acetonitrile solutions of the monomer and LiClO4 supporting electrolyte. The redox behaviour of the polymer coated electrodes was studied in dry acetonitrile and in acetonitrile + water mixtures by cyclic voltammetry, in situ UV-visible spectrophotometry and ex situ Fourier transform IR spectroscopy. Irreversible degradation of the redox activity of the PVCz film was observed in a solution containing 10% H2O in CH3CN, and this is attributed to the nucleophilic reaction of water with radical cations of the polymer. By contrast, it was found that the loss of redox activity observed in a solution containing 10% acetonitrile in H2O could be reversed by transferring the sample to dry acetonitrile. This surprising result is rationalized in terms of reversible changes in polymer conformation in water. These changes also led to a decrease in the polymer conductivity, as shown by studies of the oxidation of ferrocene at the polymer coated electrodes.