Some aspects of the radiation processing of conducting polymers

Recently, in our laboratory (IARC), complex studies have been made on conducting polymers such as polyaniline, polypyrrole and polythiophene. Our research programme has been directed toward a better molecular understanding of the structural properties controlling electronic conductivity of polymers. The most important issue of our studies within conducting polymer family includes effect of γ and electron beam irradiation on their electrical conductivity. The irradiation was performed on the samples in the form of pellets onto which aluminium electrodes had been vacuum-deposited. The relative conductivities of irradiated pellets prepared from highly conducting polyaniline, polypyrrole and polythiophene powders decreased with increase of irradiation dose under vacuum. On the other hand, in the case of irradiation under dopant atmosphere, conductivity of pellets was increased. The dramatic increase in conductivity was observed after irradiation of insulating polyaniline form (even under air atmosphere). The ESR studies suggest that the charge-transport in low doped conducting polymer can be explained by paramagnetic polaron migration along and between the polymer chains. At higher doping levels, in the case of polythiophene and polypyrrole the energetically favourable is a bipolaron state as charge carrier. (author)