DIFFUSION BEHAVIOR OF ANIONS IN POLYANILINE DURING ELECTROCHEMICAL UNDOPING .1. DEPENDENCE OF DIFFUSION-COEFFICIENT OF BF4- ON PHYSICAL STATE OF POLYANILLINE

The diffusion coefficients of BF4- in the polyaniline fibril in the course of the electrochemical undoping were estimated by using the potential step method. In this study, the diffusion of BF4- in the polyaniline was examined by the cylindrical diffusion system. The observed current-time transient during the potential step experiment was in good agreement with the current-time transient calculated from the cylindrical diffusion system, and the estimated diffusion coefficient of BF4- in the polyaniline fibril was reproducible. The diffusion coefficient of BF4- in the potential region from 3.9 to 3.6 V vs Li/Li+ was much larger than that in the potential region from 3.2 to 2.7 V vs Li/Li+. The activation energies for the diffusion of BF4- in two potential regions were obtained from Arrhenius plots. The activation energy for the diffusion of BF4- in the high potential region was less than that in the low potential region. Such a difference indicates that the physical state of the polyaniline in the high potential region is different from that in the low potential region.