Effects of molecular weight of syndiotactic polystyrene on the miscibility of the polymer blends

Abstract

To study the crystallization and the morphologies of syndiotactic polystyrenes and their blends. Synthesize the syndiotactic polystyrene by using Cp*TIcL3/MMAO catalyst system at three polymerization temperatures to obtain three different molecular weights of syndiotactic polystyrene. The three samples of sPS that ordered by the number average molecular weight (Mn) are named sPS1, sPS2, and sPS3, respectively. Blend syndiotactic polystyrene of different molecular weights with Poly(n-butyl methacrylate); (PBMA), Poly(cyclohexyI acrylate); (PCHA), Poly(ethyl methacrylate); (PEMA), Poly(alpha-methylstrene), Polyisoprene and Poly(vinyl methyl ether);(PVME) by using solvent casting method. All of the blends except sPS/PVME blends at various compositions exhibit single glass transition temperature (Tg), indicating the miscibility of the blends, which shifts to a higher temperature with increasing the sPS content and the increase Mn. sPS/PVME blends with PVME contents higher than 20 wt% show two Tg, indicates that the sPS/PVME blends are phase separated. The crystalline melting temperature (Tm) of sPS blends are lower than pure sPS. The crystalline melting temperature in the first scan (Tml) from the DSC results correspond to % crystallinity from the XRD results, which have the same trend in all blends. When the amorphous polymer were added, they affect to % crystallinity of all pure sPS decrease, that correspond to the Tg which Tg of sPS blends at the amorphous polymer content 10 wt% obviously decrease except sPS/Poly(alpha-methylstryrene) blends.