SYNDIOTACTIC POLYSTYRENE-BASED BLENDS - CRYSTALLIZATION AND PHASE-STRUCTURE

The Crystallization from the melt, the morphology and the miscibility of syndiotactic Polystyrene/poly(vinyl methyl ether) (SPS/PVME) blends and syndiotactic polystyrene/poly(2,6-dimethyl-1,4-diphenylene oxide) (SPS/PPO) blends have been analysed by differential scanning calorimetry and optical microscopy. It was found that the kinetic parameters are strongly altered by the blending and by the crystallization conditions. In particular, the spherulite growth rate of SPS decreases if PPO is added, whereas it increases in the case of SPS/PVME blends. The half-time of crystallization is drastically increased by the presence of both PPO and PVME. The PVME segregated into spherical domains in the SPS intraspherulitic region, whereas there is no microscopic evidence that the PPO forms segregated domains. These results were correlated to the viscosity of the melt and the degree of miscibility of the blends. It was concluded that the SPS/PPO system is completely miscible in the amorphous phase, whereas PVME forms with SPS a two-phase separated system. This conclusion results in agreement with the presence of one T(g), composition-dependent, for the SPS/PPO blend, and of two T(g) for the SPS/PVME blends.