DC Conductivity of some Polyazomethines

Eight polyazomethine polymers were synthesized with different backbone structures and side groups attached. Five of these polymers, with high melting point, were subjected to DC conductivity (σ) measurements versus temperature change (300–500K). The annealed samples show consistent behaviour. The [log σ] versus [1/T] curves for the undoped polymers can be divided into two parts: a nearly independent (low temperature) region, and an activated (high temperature) region with an activation energy of about 0·5eV. The values of σ for the undoped polymers lie in the dielectric domain (σ≃10-11–10-10Scm-1). Iodine and concentrated sulphuric acid were used as dopants. The doped polymers show a sudden dramatic increase in σ up to 10-7–10-6Scm-1, which brings the doped polymers into the semiconductor domain. This was sometimes accomplished in steps. All the results are interpreted by the energy band model with the formation of bipolarons.