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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 ␣ position to the original initiator sites and was used to initiate the ATRP of styrene with a CuBr/2,2Ј-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.

A new tetrafunctional initiator, di(hydroxyethyl)‐2,9‐dibromosebacate (DHEDBS) [HOCH2CH2OOCCHBr(CH2)6CHBrCOOCH2CH2OH], was synthesized and used in preparation of A2B2 miktoarm star copolymers, (polystyrene)2/ [poly(1,3‐dioxepane)]2 [S‐(PSt)2(PDOP)2], by transformation of atom transfer radical polymerization (ATRP) to cationic ring‐opening polymerization (CROP). First, two‐armed PSt with two primary hydroxyl groups sited at the center of macromolecule [(PStBr)2(OH)2] was obtained by ATRP of St with the initiation system of DHEDBS/CuBr/bpy, and used as a chain‐transfer agent in the CROP of DOP with triflic acid as the initiator. Therefore, A2B2 miktoarm star copolymer S‐(PSt)2(PDOP)2 was formed. Its structure was confirmed by the 1H NMR spectrum. Gel permeation chromatography (GPC) curves show that the polymers obtained have a relatively narrow molecular weight distribution. The hydrolysis product of S‐(PSt)2(PDOP)2 was also characterized by 1H NMR and GPC. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 437–445, 2001

The synthesis of A4B4 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 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 1H NMR. The macroinitiator C(PTHF)4Br4 was hydrolyzed to afford PTHF arms. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2134–2142, 2001