Conductivity and thermopower of blends of polyaniline with insulating polymers (PETG and PMMA)

We have measured the temperature dependence of the conductivity and thermoelectric power of conducting polyaniline (PAni) dispersed in PETG copolyester and in poly(methylmethacrylate) (PMMA). Near room temperature, the PAni/PMMA blends (like unblended PAni) show a change to metallic sign for the conductivity temperature dependence, whereas this sign change does not occur for the PAni/PETG blends. As temperature decreases, the PAni/PMMA blends show a much smaller decrease of conductivity than the PAni/PETG blends and even unblended PAni. A simple model involving metallic conduction in addition to tunnelling between metallic particles can give a good account of all the conductivity data. The thermopower of all the blends is small and increases as temperature increases.