Three-phase model of two-component blends consisting of a polystyrene-polybutadiene star block copolymer and a polystyrene homopolymer

Based on results of atomic force microscopy and dynamic mechanical analysis applied on binary blends of polystyrene (PS)-poly­butadiene (PB) star block copolymers (ST3) having different compositions, a three-phase morphology that comprises PB-rich, PS/PB-mixed and PS-rich phase has been found. The pronounced enhancement of toughness in blends with 20-30 wt.-% PS homopolymer compared to pure ST3 can be understood by improvement of the stress transfer between the microdomains through the additional hPS-induced interfacial PS/PB-mixed volume fraction and the co-continuous morphology.