DC CONDUCTIVITY OF SOME POLYAZOMETHINES

Eight polyazomethine polymers were synthesized with different backbone structures and side groups attached. Five of these polymers, with hig h melting point, were subjected to DC conductivity (sigma) measurement s versus temperature change (300-500 K). The annealed samples show con sistent behaviour. The [log sigma] versus [1/T] curves for the undoped polymers can be divided into two parts: a nearly independent (low tem perature) region, and an activated (high temperature) region with an a ctivation energy of about 0.5 eV. The values of a for the undoped poly mers lie in the dielectric domain (sigma similar or equal to 10(-11)-1 0(-10) S cm(-1)). Iodine and concentrated sulphuric acid were used as dopants. The doped polymers show a sudden dramatic increase in a up to 10(-7)-10(-6) S cm(-1), which brings the doped polymers into the semi conductor domain. This was sometimes accomplished in steps. All the re sults are interpreted by the energy band model with the formation of b ipolarons.