Glass transition in ethylene-vinylacetate copolymers analyzed by combined dielectric and X-ray scattering experiments

Abstract

We studied the peculiarities of the glass transition in semicrystalline polymers by simultaneous temperature-dependent small angle X-ray scattering experiments and dielectric relaxation studies on ethylene-vinylacetate statistical copolymers. Properties of the beta-relaxations, which represents the glass transition of these systems, change systematically with the comonomer content and the temperature. The broadening of the dielectric loss spectra, indicative of large variations in the sequence mobility in the amorphous regions, increases with the crystallinity, and on approaching T-g also explicitly with decreasing temperature. While the first effect is due to the special structure of the disordered regions, where the presence of fixed entanglements and loops results in motional restrictions, the temperature effect near T-g may reflect the increase in the correlation length of the beta-process.