Polyurethane Toughened Polystyrene With In‐Situ Compatibilization and Controlled Hierarchical Microphase Structure by “One‐Pot” Cascade Radical and Step‐Growth Polymerizations

The microphase structure of multicomponent and multiphase polymers plays a critical role in determining their properties. A one‐pot strategy integrating radical and step‐growth polymerizations is developed to prepare polyurethane (PU)/polystyrene (PS) alloy (PUS) with a high‐impact polystyrene (HIPS)‐like salami morphology. Di‐(6‐hydroxylhexyl) maleate (HMH) is introduced as a dual‐role monomer to form PS‐ g ‐PU as a compatibilizer in situ. When dibutyltin dilaurate (DBTDL) was initially mixed with poly(tetramethylene glycol), HMH, 4,4′‐methylenebis(phenyl isocyanate), and styrene, delaying benzoyl peroxide (BPO) addition allowed the PU particles (0.1∼0.3 µm) to aggregate into larger PU microdomains. In contrast, when BPO was initially mixed with the monomers, delaying DBTDL addition promoted the formation of PS‐grafted HMH, followed by their incorporation into PU chains and forming a salami‐like morphology. The optimized PUS exhibited a notched impact and tensile strengths of 10.1 kJ/m 2 and 45.5 MPa, respectively (9.4 kJ/m 2 and 30.9 MPa for commercial HIPS). This work provides a one‐pot route for coupling chain‐growth and step‐growth polymerizations to prepare PUS with controlled phase structures and in‐situ compatibilization.