Poly(vinyl chloride)-based miscible blends: Changes induced in the structural characteristics and in dielectric ? 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: crystalline poly(ϵ-caprolactone) (PCL) and glassy syndiotactic poly(methylmethacrylate) (sPMMA). The dynamics of the α relaxation of PVC is severely changed by blending it with PCL or sPMMA becoming faster or slower, respectively. Simultaneously, the shape of the relaxation function is being importantly altered. It shows a stronger non-Debye character being broader and strongly 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 been performed in order to assure the absence of crystallinity in the blends, and some small variations can be deduced at the level of interchain structural correlations of PVC.