Conductivity evolution of polypyrrole thin films with aging

Conductivity has been measured as a function of time ta during aging, and as a function of temperature for different aging times, on differently doped polypyrrole (PPy) in various conditions. We show that for the samples aged below 150 °C, a single expression describes both the temperature and the aging time dependences of the conductivity, In σ(ta,T) α −(ta / T)1/2. This corresponds to a hopping process between conducting grains separated by expanding insulating barriers upon aging. Moreover, the aging kinetics for different temperatures can be deduced from each others with scaling laws. The relative stabilities of PPy with various dopants have been compared. Slight deviations from the above behaviour, observed when aging above 150 °C, can be accounted for by a generalization of the model.