REDOX SWITCHING OF POLYANILINE FILMS - LOW-TEMPERATURE STUDIES

Polyaniline films can be switched rapidly between insulating (reduced) and conducting (oxidized) states. The kinetics of the processes involved in the redox switching have been studied using ultramicroelectrodes, which have the advantage that iR errors are minimized. The leucoemeraldine/emeraldine transformation has been studied in HClO4.5.5H2O over the temperature range 220 - 300 K. The polyaniline films can still be switched rapidly at the lowest temperature studied. Potentiostatic oxidation transients exhibit a peaked shape characteristic of a nucleation and growth process. The monotonic reduction transients, on the other hand, are much faster and appear to be controlled by the RC time constant. The temperature dependence of the redox switching processes has been investigated and related to electron and proton transfer as well as to anion transport in the polymer film.