Electronic conductivity of pyrrole and aniline thin films polymerized by plasma

In this article, we present a study of the influence of temperature and humidity on the electric conductivity of polyaniline and polypyrrole thin films doped with iodine and synthesized by plasma (PAn/I and PPy/I, respectively). The polymers presented the characteristic ohmic conduction mechanism via electrons; however, the conductivity was much lower than that presented by the polymers obtained by traditional chemical oxidation. We submitted the polymers to heating-cooling cycles to study the temperature dependence of the conductivity. During the heating stage of the cycles, the electric conductivity of PPy/I showed a strong dependence on the humidity content. However, during the cooling step, the plots of conductivity, as a function of the inverse temperature of PPy/I and PAn/I, showed typical Arrhenius behavior. The activation energy of PPy/I had an average value of 1.1 +/- 0.1 eV and was independent of the reaction time, whereas PAn/I presented a more complex behavior with activation energies that depended on the reaction time and the regional crystallinity induced in the heating step of the cycles. All the activation energies were below 2 eV, which places them in the semiconductor regime. (C) 2000 John Wiley & Sons, Inc.