Synthesis of Starlike PtBA-g-PEO Amphiphilic Graft Copolymer via Highly Efficient Cu-Catalyzed SET-NRC Reaction at Ambient Temperature

Two new amphiphilic star graft copolymers bearing hydrophobic poly(tert-butyl acrylate) backbone and hydrophilic poly(ethylene oxide) (PEO) side chains with different molecular weights were synthesized by sequential reversible addition fragmentation chain transfer (RAFT) polymerization and single electron transfer-nitroxide radical coupling (SET-NRC) reaction under mild conditions. RAFT homopolymerization of tert-butyl 2-((2-bromopropanoyloxy)methyl)acrylate was mediated by a four-armed chain transfer agent in a controlled way to afford a well-defined starlike backbone with a narrow molecular weight distribution (M-w/M-n = 1.26). The target poly(tert-butyl acrylate)-g-PEO (PtBA-g-PEO) star graft copolymers were synthesized by SET-NRC reaction between Br-containing PtBA-based starlike backbone and PEO end functionalized with 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) group using copper/N,N,N',N'-N"-pentamethyldiethylenetriamine as catalytic system at ambient temperature via grafting-onto strategy. The critical micelle concentration values of the obtained amphiphilic star graft copolymers in aqueous media and brine were determined by fluorescence probe technique using pyrene as probe. Diverse micellar morphologies were formed by varying the content of hydrophilic PEO segment as well as the initial concentration of stock solution. In addition, poly(acrylic acid)-g-PEO double hydrophilic star graft copolymers were obtained by selective acidic hydrolysis of hydrophobic PtBA starlike backbone without affecting PEO side chains. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 23-34, 2011