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

Poly(N-vinylcarbazole) (PVCz) films were prepared by potentiostatic de position onto gold, platinum and indium tin oxide (ITO) electrodes fro m acetonitrile solutions of the monomer and LiClO4 supporting electrol yte. The redox behaviour of the polymer coated electrodes was studied in dry acetonitrile and in acetonitrile + water mixtures by cyclic vol tammetry, in situ UV-visible spectrophotometry and ex situ Fourier tra nsform IR spectroscopy. Irreversible degradation of the redox activity of the PVCz film was observed in a solution containing 10% H2O in CH3 CN, and this is attributed to the nucleophilic reaction of water with radical cations of the polymer. By contrast, it was found that the los s of redox activity observed in a solution containing 10% acetonitrile in H2O could be reversed by transferring the sample to dry acetonitri le. This surprising result is rationalized in terms of reversible chan ges in polymer conformation in water. These changes also led to a decr ease in the polymer conductivity, as shown by studies of the oxidation of ferrocene at the polymer coated electrodes.