Conducting polymers prepared by oxidative polymerization: polyaniline

Abstract

Polyaniline (PANI) is one of the most intensively investigated polymers during the last decade. The establishment of the scientific principles allowing regulation of its properties, determining the potential application areas (alternative energy sources and transformers, media for erasable optical information storage, non-linear optics, membranes, etc.) is an important scientific problem. We have shown for the first time that the behavior of this polymer is subject to the same basic principles as the polymerization process itself. Both the polymerization of aniline and the subsequent transformations of polyaniline have to be regarded as typical redox processes, where the direction and establishment of equilibrium are dependent on the oxidation potentials and concentrations of the reactants (and also on pH of the medium, affecting the values of oxidation potential of the reactants). Such an approach allows us to identify the oxidative polymerization of aniline (and presumably of thiophene and pyrrole) as a new area in cationic polymerization, wherein the conditions of initiation, propagation and termination of the chains can be expressed by means of the electrochemical potential of the system. Furthermore, this allows an elucidation of the key problems related to the main types of transformations of this polymer (the so-called oxidative and non-oxidative doping of polyaniline). It also gave us a reason to suggest a novel original classification of the numerous potential application areas of PANI.