In situ dc conductivity study of the redox transformations and relaxation of polyaniline films

The insulator to conductor and conductor to insulator conversions of polyan iline have been studied by the in situ conductivity technique. Polyaniline was deposited by electropolymerization of aniline connecting two or more ba nds of gold electrodes. The gap between two gold stripes was 2 mu m. Slow r elaxation and hysteresis effects have been observed in different electrolyt e solutions in the temperature interval from 5 to 45 degrees C. The duratio n of the change of the resistance after a potential step is small (tens of seconds) in the potential region where the film is conducting, however, the relaxation may last for hours during conducting to insulating transitions. In the latter case, the behavior does not obey a simple logarithmic relaxa tion because at least two distinct slopes can be determined in the R versus In t curves. The conductivity relaxation is in accordance with the previou s results obtained by other techniques and can be explained by the existing theories. (C) 2000 Elsevier Science S.A. All rights reserved.