Charge Transport of Hydrochloric Acid Doped Polyaniline and Poly(o-toluidine) Fibers: Role of Processing

We report the results of transport (temperature dependent dc conductivity, thermoelectric power, and microwave frequency conductivity, and dielectric constant) and structural studies for hydrochloric acid doped polyaniline (PAN-HCl) fibers 4-fold stretched at 300, 350, and 400 °C and the results of dc conductivity for its methyl ring-substituted derivative, poly(o-toluidine) (POT-HCl) fibers. For the PAN-HCl fibers,with increasing stretching temperatures, the system shows greater localization, as indicated by the decreasing conductivity with stronger temperature dependence and decreasing microwave dielectric constant with weaker temperature dependence. This is in accord with the observed decreasing crystallinity with increasing processing temperature. The interrupted metallic strands model is used to account for the microwave results assuming that the size of the metallic regions increases linearly with temperature. For the POT-HCl fiber, the conductivity is similar to that for the POT-HCl powder. When the fiber is stretched 3-fold, the conductivity increases almost 1 order of magnitude while the temperature dependence changes only slightly, in agreement with the short localization length in the system.