Effect of the processing parameters on the conductivity mechanism of polyaniline films
Résumé
In this work, we report a study of the effect of the solvent type and the casting temperature on the electrical properties of pure fully doped conducting polymer films (polyaniline). The polyaniline was dispersed in two different solvents (dichloro-acetic acid, and a mixture of dichloro-acetic acid and formic acid). Previous work showed that around 318 K, a second order liquid-liquid structural transition occurs in the dispersions. Consequently, we have chosen three different casting temperatures (298 K ‘room temperature', 318 K and 353 K). The electrical properties of the cast films were investigated in the frequency range 100 Hz - 1 MHz. The temperature was varied between 20 K and 300 K. We found that the DC conductivity is governed by Mott's three-dimensional variable range hopping (3D VRH) model for PANI/DCAA films. The different Mott's parameters have been evaluated. In the PANI/DCAA-FA films, the conduction mechanism occurring was found to follow a fluctuation induced tunnelling model (FIT). The different FIT parameters have been also evaluated. The dependence of such values on the processing parameters is discussed. The X-ray diffraction technique was also used to find a reasonable correlation between microstructure and electrical properties.