Switching Potentials and Conductivity of Polypyrrole Films Prepared in the Ionic Liquid 1-Butyl-3-methylimidazolium Hexafluorophosphate

Abstract

Polypyrrole (ppy) and poly(N-methylpyrrole) (pmpy) films were prepared galvanostatically at the ring of a rotating ring-disk electrode from the corresponding monomers dissolved in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate Rotating ring-disk voltammetry was used to determine switching potentials and conductivity of the films while immersed in Switching potentials of and V vs. the cobaltocenium/cobaltocene couple, were determined for the ppy and pmpy films, respectively, from negative potential scan voltammograms. Positive potential scan voltammetry was used to obtain the potential-dependent conductivity of the films as the films switched from their insulating (at potentials more negative than switching potential) to a quasi-metallic state. Two different computational models (nonlinear vs. linear conductance gradients) and two different redox probes and decamethylferrocenium/decamethylferrocene) were used in the calculation of the film conductivity. The conductivity of the ppy films increased by an order of magnitude for every mV change in the applied potential. At potentials less than the switching potential, the conductivity of the pmpy films increased tenfold for every mV change in the applied potential. At potentials greater than the switching potential, the pmpy films required a 200 mV change to induce the same degree of change in film conductivity. © 2004 The Electrochemical Society. All rights reserved.