THERMAL-DEGRADATION OF POLYPYRROLE - EFFECT OF TEMPERATURE AND FILM THICKNESS

Thermal degradation of a series of polypyrrole films doped with p-toluene sulfonate has been investigated by examining the effect of film thickness (12-68 mum) and temperature (70-150-degrees-C) on the rate of decay of electrical conductivity. The kinetics are complex: for thin films and thick films at higher temperatures, the decay is proportional to t1/2 and a similarity to diffusion kinetics is noted; at low temperatures the conductivity decay of thicker films follows first-order kinetics for at least 100 h. It is suggested that the decay is explained by oxidation and that either chemical reaction or oxygen diffusion will be rate determining, depending on the film thickness and ageing temperature. At higher temperatures, the deduced diffusion coefficient D was independent of film thickness. The Arrhenius plot of D or of the time-temperature shift factor a(T) showed a change of slope at 90-degrees-C, suggesting the possibility of a glass transition temperature in the film.