Electrical conductivity of annealed polyaniline

Abstract

The electrical conductivity of chemically synthesized and annealed polyaniline has been investigated. The room-temperature conductivity varies with the time and the temperature of annealing, and exhibits a maximum peak on its time-dependence curves for the polymer annealed above 120 °C. The time showing the maximum peak of the conductivity shifts to the shorter side with higher annealing temperature. The linear dependence of the conductivity on temperature with T−1/2 is observed in all samples as explained for this polymer with the quasi-one-dimensional variable-range-hopping processes. In the initial stage of annealing, the conductivity increases in the whole temperature range without varying the exponential factor of the variable range hopping. This indicates that the density of states remains unchanged in this stage. The results concerning the pre-exponential factor of the quasi-one-dimensional variable-range-hopping mechanism demonstrate the increase of the mean free time, the transverse localization length, and the interchain transfer integral with annealing. X-ray-diffraction patterns exhibit the generation of regularized amorphous structure in annealed samples, which leads to the enlargement of the interchain interaction. The results show the increase of regularity of the polymer chain at first, and the phase transition to the loose-packed and ordered structure in next stage of annealing.