Summary
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.