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(CH2OCH2CHBrCOCl)(4)] with silver perchlorate was used to initiate the CROP of tetrahydrofuran. The obtained polymer contained four secondary bromine groups at the alpha 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 H-1 NMR. The macroinitiator C(PTHF),Br, was hydrolyzed to afford PTHF arms. (C) 2001 John Wiley & Sons, Inc.