DEPENDENCE OF CONDUCTIVITY OF POLYPYRROLE FILM DOPED WITH PARA-PHENOL SULFONATE ON SOLUTION PH

The conductivity of polypyrrole films doped with p-phenol sulfonate decreases with increasing pH of aqueous solutions in which the films are immersed. A linear relationship is established between the relative ratio of the conductivity. change and the degree of dissociation of hydroxyl groups of p-phenol sulfonate doped in the film, indicating that the decrease in the conductivity results from an increase in bindings of positive charges of polypyrrole with phenoxide ions produced by dissociation of hydroxyl groups of the dopant. The formation of the phenoxide ions accompanies the incorporation of electrolyte cations into the film to compensate the generated negative charges. The rate of the conductance change caused by changing solution pH is then controlled by the diffusion rate of electrolyte cations in the polypyrrole films and is high for cations of small ionic radius. © 1990, The Electrochemical Society, Inc. All rights reserved.