CONDUCTIVITY EVOLUTION OF POLYPYRROLE THIN-FILMS WITH AGING

Conductivity has been measured as a function of time t(a) during aging , and as a function of temperature for different aging times, on diffe rently doped polypyrrole (PPy) in various conditions. We show that for the samples aged below 150 degrees C, a single expression describes b oth the temperature and the aging time dependences of the conductivity , In sigma(t(a),T)proportional to-(t(a)/T)(1/2). This corresponds to a hopping process between conducting grains separated by expanding insu lating barriers upon aging. Moreover, the aging kinetics for different temperatures can be deduced from each others with scaling laws. The r elative stabilities of PPy with various dopants have been compared. Sl ight deviations from the above behaviour, observed when aging above 15 0 degrees C, can be accounted for by a generalization of the model.