GLASS-TRANSITION IN ETHYLENE-VINYLACETATE COPOLYMERS ANALYZED BY COMBINED DIELECTRIC AND X-RAY-SCATTERING EXPERIMENTS

We studied the peculiarities of the glass transition in semicrystallin e polymers by simultaneous temperature-dependent small angle X-ray sca ttering experiments and dielectric relaxation studies on ethylene-viny lacetate statistical copolymers. Properties of the beta-relaxations, w hich represents the glass transition of these systems, change systemat ically 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 crystal linity, and on approaching T-g also explicitly with decreasing tempera ture. While the first effect is due to the special structure of the di sordered 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.