Block and star block copolymers by mechanism transformation. VI. Synthesis and characterization of A₄B₄ miktoarm star copolymers consisting of polystyrene and polytetrahydrofuran prepared by cationic ring‐opening polymerization and atom transfer radical polymerization

The synthesis of A 4 B 4 miktoarm star copolymers, where A is polytetrahydrofuran (PTHF) and B is polystyrene (PSt), was accomplished with orthogonal initiators and consecutive cationic ring‐opening polymerization (CROP) and atom transfer radical polymerization (ATRP). The compound formed in situ from the reaction of 3‐{2,2‐bis[2‐bromo‐2‐(chlorocarbonyl) ethoxy] methyl‐3‐(2‐chlorocarbonyl) ethoxy} propoxyl‐2‐bromopropanoyl chloride [C(CH 2 OCH 2 CHBrCOCl) 4 ] with silver perchlorate was used to initiate the CROP of tetrahydrofuran. The obtained polymer contained four secondary bromine groups at the α position to the original initiator sites and was used to initiate the ATRP of styrene with a CuBr/2,2′‐bipyridine catalyst to form a C(PTHF) 4 (PSt) 4 miktoarm star copolymer. The miktoarm copolymer was characterized by gel permeation chromatography and 1 H NMR. The macroinitiator C(PTHF) 4 Br 4 was hydrolyzed to afford PTHF arms.