Compatibilizing effect of a diblock copolymer of isotactic polystyrene and isotactic polypropylene in blends of the corresponding homopolymers

Abstract

AbstractA high molecular weight polymer mixture was obtained from a sequential Ziegler–Natta polymerization of styrene and propylene. After removing unwanted homopolymers from the reaction product, the remaining copolymer was subjected to extensive molecular and morphological characterization. The results of these experiments indicate that the purified material is a diblock copolymer of isotactic polystyrene and isotactic polypropylene, with each block having a molecular weight in the range of 225,000 g/mol. This block copolymer was incorporated in varying amounts into blends of isotactic polystyrene and isotactic polypropylene homopolymers. At low concentrations of copolymer (<20 wt %), the diblock functions as a dispersing agent, significantly reducing the size of domains in the heterogeneous blends. At higher copolymer concentrations, a dramatic improvement in the adhesion across the domain boundaries is also observed. The favorable effects of the copolymer on mechanical properties are demonstrated in the results of tensile impact experiments.