SYNTHESIS AND CHARACTERIZATION OF SOLUBLE POLYPYRROLE

Soluble polypyrrole(PPy) was synthesized chemically by using ammonium persulfate and dodecylbenzene sulfonic acid as an oxidant and a dopant , respectively. It was found that the soluble PPy powder as well as th e cast film contained a high concentration of free radicals detected b y an electron paramagnetic resonance spectrometer. The polymer solutio n was cast into a film with a very fine reflective surface. A thin fil m with the light transmittance fo 80% showed the surface resistivity o f 25 k Omega/square displaying an increase in the resistivity only by 20 k Omega/square compared to the resistivity of a thick film. DC cond uctivity of the PPy film fitted nicely the quasi-one-dimensional varia ble range hopping model. The bulk electrical conductivity of the cast film increased by one order during initial heating to 200 degrees C in air and changed little during isothermal heating at 200 degrees C for 120 minutes. The conductivity kept a half of the initial increase aft er cooling from 200 degrees C to room temperature. The surface resisti vity of the film, however, was found to increase dramatically on heati ng at 200 degrees C in air. Since the surface resistivity showed no ch ange on heating in nitrogen atmosphere at 200 degrees C, oxidation dur ing heating caused the decrease in the conductivity of the polymer.