AC CONDUCTION PROPERTIES OF CONDUCTING POLYMER BLENDS BASED ON POLYANILINE

The composition and temperature dependence of the ac-conductivity of f ilms of conducting polymer blends has been studied in the frequency ra nge : 10 Hz - 18 GHz. The frequency dependence of the complex permitti vity dramatically changes from a dielectric to a conducting behavior f or a weight fraction of conducting polymer corresponding to the percol ation threshold pc determined by de-conductivity measurements. The hig h frequency dispersion of the ac-conductivity, characteristic of disor dered conductors is recovered. In addition, a ''relaxation'' process i s observed at intermediate frequencies, which can be of rather high am plitude for weight fractions slightly above p(c). The ''fractal'' natu re of the conducting polymer net seems to be responsible for this beha vior.