Photoresponsive poly(methyl methacrylate)2–(polystyrene)2 miktoarm star copolymer containing an azobenzene moiety at the core



We prepared a novel miktoarm star copolymer with an azobenzene unit at the core via combination of atom transfer radical polymerization (ATRP) and nitroxide-mediated free radical polymerization (NMP) routes. For this purpose, first, mikto-functional initiator, 3, with tertiary bromide (for ATRP) and 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO) (for NMP) functionalities and an azobenzene moiety at the core was synthesized. The initiator 3 thus obtained was used in the subsequent living radical polymerization routes such as ATRP of MMA and NMP of St, respectively, to give A2B2 type miktoarm star copolymer, (PMMA)2-(PSt)2 with an azobenzene unit at the core with controlled molecular weight and low polydispersity (Mw/Mn < 1.15). The photoresponsive properties of 3 and (PMMA)2-(PSt)2 miktoarm star copolymer were investigated. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1396–1403, 2006