Synthesis of Amphiphilic A2B Star-shaped Copolymers of Polystyrene-b-[Poly(ethylene oxide)]2 via Atom Transfer Nitroxide Radical Coupling

The amphiphilic A(2)B star-shaped copolymers of polystyrene-b-[poly(ethylene oxide)](2) (PS-b-PEO2) were synthesized via the combination of atom transfer nitroxide radical coupling (ATNRC) with ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP) mechanisms. First, a novel V-shaped 2,2,6,6-tetramethylpiperidine-1-oxyl-PEO2 (TEMPO-PEO2) with a TEMPO group at middle chain was obtained by ROP of ethylene oxdie monomers using 4-(2,3-dihydroxypropoxy)-TEMPO and diphenylmethyl potassium as coinitiator. Then, the linear PS with a bromine end group (PS-Br) was obtained by ATRP of styrene monomers using ethyl 2-bromoiso-butyrate as initiator. Finally, the copolymers of PS-b-PEO2 were obtained by ATNRC between the TEMPO and bromide groups on TEMPO-PEO2 and PS-Br, respectively. The structures of target copolymers and their precursors were all well-defined by gel permeation chromatographic and nuclear magnetic resonance (H-1 NMR). (C) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 2635-2640, 2012