Asymmetric PS‐block‐(PS‐co‐PB)‐block‐PS block copolymers: morphology and deformation behavior of star block copolymer/PS blends

Abstract

Abstract The morphology and deformation behavior of blends comprising an asymmetric styrene/butadiene star block copolymer and polystyrene homopolymer (hPS) were investigated by means of transmission electron microscopy (TEM) and uniaxial tensile testing. The hPS samples used had a wide range of molecular weights. In spite of the high polystyrene (PS) content, the star block copolymer exhibited a morphology consisting apparently of a rubbery matrix, attributable to its asymmetric architecture and presence of polystyrene/polybutadiene random copolymer (PS‐co‐PB) as soft rubbery blocks. In the blends, depending on the molecular weight and modality of the added hPS and on the composition of the mixtures, different morphologies (ranging from microphase‐separated and macrophase‐separated ones to a combination of both of them) were observed. Consequently, it was possible to tailor the tensile mechanical properties based on the nature of the nanoscopic morphology of the star block copolymer/PS blends. Copyright © 2005 John Wiley & Sons, Ltd.