Influence of conformational microstructure in the molecular motions of poly(vinyl chloride)

Abstract

Conformational changes induced by physical modification (stretching) of poly(vinyl chloride) (PVC) have been investigated by means of wide angle X-ray diffraction (WAXS). The properties of the modified samples have also been studied by means of dielectric relaxation in the frequency domain in the α-relaxation region which is associated with the glass transition. Although the temperature of the loss peak is not drastically changed and the parameters describing the molecular mobility of the material are not appreciably altered within the experimental errors, the relaxation function in the frequency domain obtained in the modified samples is narrowed with respect to that obtained for the unmodified PVC. By an interpretation of the relaxation results in the frame of Ngai's coupling model, it is concluded that the modification of PVC by stretching leads to a decrease of the molecular interactions in the material. These results, as well as those obtained by WAXS, lead one to think that these changes are closely related to the fact that intrachain conformational structure of PVC has been changed during the stretching process.