Intrinsic Asymmetry, Hysteresis, and Conformational Relaxation during Redox Switching in Polypyrrole: A Coulovoltametric Study

Abstract

Theoretical coulovoltammograms associated with the evolution of anodic charges when a polypyrrole film, which was previously compacted at a strong negative potential in a 0.1 M LiClO4 propylene carbonate solution, was submitted to anodic potential sweeps were compared with experimental responses. The electrochemically stimulated conformational relaxation (ESCR) model provides a good description of either the influence of the negative potential limit, the sweep rate, the temperature, or the electrolyte concentration on the rate of electrochemical oxidation, this being initiated through conformational relaxation processes and completed under counterions diffusion control. An analysis of both anodic and cathodic experimental branches, together with theoretical conformational relaxation curves, allows to detect four different structural rearrangement processes affecting electrochemical responses: the well-known conformational relaxation effect observed only in anodic branches, a hysteresis effect on cathodic...