Electrochemical oxidation of polypyrrole under conformational relaxation control. Electrochemical relaxation model

A simple model of polymeric relaxation, associated with the electrochemical switching of polypyrrole films between their reduced (insulating) and oxidized (electronically conducting) states, offers a reasonably precise description of the form of chronoamperograms obtained after previous submission of the polymer film to cathodic potentials (which control the compactness of the neutral polymer) for long periods of time. Opening of the structure driven by anodic potential is not uniform: nucleation of conducting zones inside the neutral polymer and their overlap at long times of anodic polarization are taken into account in the model. Diffusion of counterions from the solution across the oxidized zones are also included. The definition of a relaxation time (depending on both cathodic and anodic overpotentials), and the inclusion of nucleation and diffusion processes, allows a theoretical modelling of chronoamperograms in good agreement with experimental data. This electrochemical relaxation theory is an open model including both electrochemical and polymeric magnitudes.