REINTERPRETATION OF POLYPYRROLE ELECTROCHEMISTRY AFTER CONSIDERATION OF CONFORMATIONAL RELAXATION PROCESSES

A simple model of polymeric relaxation, associated with the electroche mical 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 p revious subjection of the polymer film to cathodic potentials (which c ontrol the compactness of the neutral polymer) for long periods of tim e. The opening of the structure driven by the 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 acc ount in the model. Diffusion of counterions from the solution across t he oxidized zones is also included. The definition of a relaxation tim e (depending on both cathodic and anodic overpotentials and on tempera ture), and the inclusion of nucleation and diffusion processes, allows a theoretical simulation of chronoamperograms, in good agreement with experimental results from potential steps performed by changing the a nodic and cathodic limits or at different temperatures.