  A general technique to investigate charge storage characteristics of
conducting polymer films has been developed. A redox reaction is conducted on a
polymer film on a rotating disk electrode under potentiostatic condition so
that the rate of charging of the film equals the rate of removal of the charge
by the reaction. In an experiment on polyaniline film deposited on platinum
substrate, using Fe2+/Fe3+ in HCl as the redox system, the voltammogram shows
five distinct linear segments (bands) with discontinuity in the slope at
specific transition potentials. These bands are the same as those indicated by
ESR/Raman spectroscopy with comparable transition potentials. From the
dependence of the slopes of the bands on concentration of ferrous and ferric
ions, it was possible to estimate the energies of the charge carrier in
different bands. It is shown that the charge storage in the film is capacitive.
