ac conduction properties of conducting polymer blends based on polyaniline

The composition and temperature dependence of the ac-conductivity of films of conducting polymer blends has been studied in the frequency range : 10 Hz – 18 GHz. The frequency dependence of the complex permittivity dramatically changes from a dielectric to a conducting behavior for a weight fraction of conducting polymer corresponding to the percolation threshold pc determined by dc-conductivity measurements. The high frequency dispersion of the ac-conductivity, characteristic of disordered conductors is recovered. In addition, a “relaxation” process is observed at intermediate frequencies, which can be of rather high amplitude for weight fractions slightly above pc. The “fractal” nature of the conducting polymer net seems to be responsible for this behavior.