STRUCTURAL STUDIES OF POLY(PARA-PHENYLENE SELENIDE) DOPED WITH SULFUR-TRIOXIDE

Poly(p-phenylene selenide) (PPSe) was prepared by condensation polymerization of 2,4 dibromobenzene and sodium selenide. The synthesis product in the form of powder was purified. The structure of the resulting polymer was investigated by infrared spectroscopy, wide-angle X-ray spectroscopy, electron diffraction, ultraviolet, electron spin resonance and elemental analysis. H-1-nuclear magnetic resonance (NMR) solid measurements were used to determine the molecular dynamics for undoped and SO3-doped PPSe. The NMR investigations for undoped PPSe have shown that there are no essential differences in the structure and molecular motion between PPSe and PPS. After doping PPSe with SO3, contrary to PPS, a third component of relaxation time, T1, is observed. The relaxation times for this component are connected to the interaction of protons with paramagnetic centres which are generated as a result of the doping process. The electrical conductivity of SO3-doped PPSe at the beginning of the doping process rapidly increased to about 6 x 10(-6) S cm-1 and then decreased more than one order of magnitude because of the chemical reaction which had occurred.