POTENTIOSTATIC PULSE AND IMPEDANCE INVESTIGATIONS OF THE REDOX PROCESS IN POLYANILINE FILMS

PANI films of thicknesses from 0.06 to 7 mu m were investigated by the potentiostatic pulse method and EIS. The films behaved very similar i n respect to both methods over the whole range of thicknesses. The oxi dized film can be described as a battery electrode with a specific cap acity as high as 130Fcm(-3). The series resistance of the oxidized fil m is much smaller than the electrolyte resistance. The reduced film ha s a high series resistance of about 4k Omega cm. For the reduced him t he capacity of the interface metal-polymer is detected in the impedanc e spectra. Both impedance spectra and potentiostatic current transient s indicate that the oxidation of PANI is an inhomogeneous process. We conclude from our measurements, that the transition follows a sequence of nucleation and growth of conducting zones, perpendicular to the su bstrate electrode. Partially oxidized polymer films can be frozen-in. The impedance spectra of these intermediate states are interpreted on the basis of a geometrical model.