Polyaniline: a new concept in conducting polymers

Abstract

The analytically pure base form of polyaniline, {A figure is presented}, corresponding to the emeraldine oxidation state is converted from an insulator (σ {A figure is presented} 10-10S/cm) to a metal (σ {A figure is presented} 5 S/cm) by treatment with {A figure is presented} 1M aqueous HCl to form the corresponding salt, emeraldine hydrochloride, {A figure is presented}. This involves a new type of doping of a conducting polymer in that the number of electrons associated with the polymer undergoes no change during the protonic acid doping process. The metallic emeraldine hydrochloride is believed to be a delocalized poly(semiquinone radical cation) having a polaron conduction band, with most of the positive charge residing on the nitrogen atoms. It exhibits a finite density of states at the Fermi energy. © 1987.