Optical Absorption and ESR Studies of Poly(p-phenylene sulfide) Doped with Sulfur Trioxide

Abstract

Optical absorption and ESR spectra of SO3-doped poly(p-phenylene sulfide) (PPS) with relatively high conductivity were measured. Two absorption bands were observed at 0.9 and 3.1 eV at the initial doping state. The intensity of these two bands increased with the rise of doping level. ESR spectra with a g-value of 2.0075 were observed for the PPS-SO3 system at the same doping level as that of absorption spectra. The intensity of ESR signals increased with the doping level, while the linewidth showed a nearly constant value of 3.6 gauss. The spin density of the PPS-SO3 system increased monotonously with the SO3 concentration. In both cases of optical absorption and ESR spectra of SO3-doped PPS, the spectral intensity increased slightly under UV-light irradiation, while these spectra were little affected by the near IR-light irradiation. These spectroscopic results suggest the presence of sulfur-centered radical-cations rather than a bipolaron state. Two intense bands of the PPS-SO3 system observed at 0.9 and 3.1 eV were considered to be assigned to electronic transitions from low lying occupied bands of PPS to the singly occupied highest band.