Poly(vinyl chloride)-based miscible blends: Changes induced in the structural characteristics and in dielectric alpha relaxation of pure poly(vinyl chloride)

In this work we investigate by means of dielectric relaxation spectroscopy how segmental motions occurring in poly(vinyl chloride) (PVC) are modified by blending of PVC with small amounts of two different homopolymers: crysta lline poly(epsilon-caprolactone) (PCL) and glassy syndiotactic poly(methylm ethacrylate) (sPMMA). The dynamics of the ct relaxation of PVC is severely changed by blending it with PCL or sPMMA becoming faster or slower, respect ively. Simultaneously, the shape of the relaxation function is being import antly altered. It shows a stronger non-Debye character being broader and st rongly temperature-dependent. This fact leads us to calculate distributions of relaxation times for the blends that are wider in comparison to the one obtained for pure PVC. Complementary X-ray diffraction measurements have b een performed in order to assure the absence of crystallinity in the blends , and some small variations can be deduced at the level of interchain struc tural correlations of PVC. (C) 2000 John Wiley & Sons.