ELECTRICAL PROPERTY OF POLYPYRROLE-INSULATING POLYMER COMPOSITE

PMMA small spheres were coated with polypyrrole by chemical polymeriza tion utilizing FeCl3 as a catalyst. Polypyrrole-PMMA composite has bee n prepared by the hot press of the mixture of polypyrrole coated PMMA spheres and non-coated PMMA spheres with appropriate concentration. Po lypyrrole-PE composite has also been prepared by a similar method. Ele ctrical 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 c an be explained by a percolation model. That is, at this concentration electrodes are considered to be bridged by conducting path (polypyrro le). By taking thickness of polypyrrole layer into consideration the c oncentration of polypyrrole at the percolation threshold is evaluated to be less than 0.1%.