Electropolymerization of pyrrole and electrochemical study of polypyrrole: 1. Evidence for structural diversity of polypyrrole

Conventional electropolymerization of pyrrole produces polypyrrole characterized voltammetrically by a single oxidation wave (ca. 0.01 V vs. Ag/AgCl) followed by a broad plateau. This was considered to be an inherent property of electrosynthesized polypyrrole, and intensive research based on such knowledge was carried out in the past. The present studies of electrochemical properties of polypyrrole prepared at extremely low formation potentials or currents reveal that polypyrrole may exhibit additional oxidation waves at potentials more negative than those normally observed. A number of cyclic voltammograms manifest a great structural diversity in polypyrrole doped by the same anion. The fact that the trace-crossing may not appear in some cases and, on the other hand, may remain after the electrode has become polymer-coated in other cases leads to the conclusion that the nucleation step is not the only factor responsible for the trace-crossing. (C) 1999 Elsevier Science Ltd. All rights reserved.