Coexistence of chemical and electrochemical polymerization mechanisms during pyrrole oxidation

Summary form only given. The generation of polypyrrole by both chemical and electrochemical ways has received increasing interest in the last decade. When conducting polypyrrole is electrogenerated on a platinum electrode, the liberation of two protons per unit of monomer incorporated into the polymer chain takes place. This leads to a fast pH decrease around the electrode. On the other hand the chemical generation of non conducting polypyrrole in strong acid solutions, is well known. In this work electrochemical evidences for the coexistence of both ways of synthesis of polypyrrole, during pyrrole electrooxidation, are presented. When a pyrrole solution is polarized at potentials higher than that of pyrrole oxidation, the simultaneous generation of electrochemical and chemical polypyrrole takes place. The chemical process is manifested by the formation of a dark cloud of polymer around the electrode. The parallel deposition on the electrode of both products promotes the formation of a mixed material, with a conjugated network (electrochemically generated) and partially saturated polymer (chemically originated). The final composition of polymer will depend on the kinetic control of both processes.