Dynamic-Mechanical And Light-Scattering Study Of The Glass-Transition Of Poly(Vinylacetate) And A Poly(Vinylacetate) Plus Poly(4-Hydroxystyrene) Blend

The dynamics of poly(vinylacetate) (PVAc) and of a blend of PVAc and 20% in weight of poly(4-hydoxystyrene) have been studied in the glass transition region using dynamic-mechanical and photon-correlation spectroscopies. Both kinds of data show the overlapping of the main alpha relaxation with a faster one. The complex part of the elastic modulus shows the existence of a beta' sub-T-g transition overlapping with the alpha and beta transitions. As a consequence, at least two Kohlraush-Williams-Watts terms are needed to describe the relaxation functions. The results show a good agreement with the predictions of the mode coupling theory except for the fact that the calculated critical temperature seems to be lower than the calorimetric glass transition temperature.