Comparison of electronic transport in polyaniline blends, polyaniline and polypyrrole

The conductivity of PAni/PETG copolyester blends shows the expected reduction compared to unblended PAni, but PAni/PMMA (and PAni/PVC blends at lower temperatures) show a larger conductivity. SEM images indicate that the different behaviour of the blends appears to be associated with greater granularity retained by the PAni particles dispersed in PETG. The conductivities of the more highly conducting PAni blends, like PAni-CSA and its blends with PMMA measured by other authors, show a change to metallic sign for the temperature dependence near room temperature — simple models combining hopping/tunnelling with metallic conduction are consistent with the conductivity except at very low temperatures. The thermopower of PAni blends shows a remarkable similarity for blends with different insulating polymers and widely varying conductivity. For polypyrrole samples of very different conductivity, the change to metallic sign for conductivity near room temperature does not occur, indicating a much smaller ‘metallic’ resistance contribution. Nevertheless, the thermopower of polypyrrole, like that of PAni and PAni blends, is of metallic size and generally increases with temperature, as expected for metallic diffusion thermopower.