ELECTRICAL PROPERTY OF POLYPYRROLE-INSULATING POLYMER COMPOSITE

PMMA small spheres were coated with polypyrrole by chemical polymerization utilizing FeCl3 as a catalyst. Polypyrrole-PMMA composite has been prepared by the hot press of the mixture of polypyrrole coated PMMA spheres and non-coated PMMA spheres with appropriate concentration. Polypyrrole-PE composite has also been prepared by a similar method. Electrical conductivity has been controlled in the wide range (10(-17)-10(1)S/cm) by changing the concentration of coated spheres in non-coated spheres. That is, when the concentration of PPy coated sphere exceeds 10-20% remarkable enhancement of conductivity by more than 17 orders of magnitude was observed. The activation energy of conductivity also changed drastically at this concentration. Low thermoelectric power of 6muV/K was evaluated for the composite of coated sphere concentration exceeding 20%. This insulator-metal transition like characteristics can be explained by a percolation model. That is, at this concentration electrodes are considered to be bridged by conducting path (polypyrrole). By taking thickness of polypyrrole layer into consideration the concentration of polypyrrole at the percolation threshold is evaluated to be less than 0.1%.