PAA-g-PPO Amphiphilic Graft Copolymer: Synthesis and Diverse Micellar Morphologies

A series of well-defined amphiphilic graft copolymers consisting of hydrophilic poly(acrylic acid) backbone and hydrophobic poly(propylene oxide) side chains were synthesized by sequential reversible addition-fragmentation chain transfer (RAFT) polymerization and atom transfer nitroxide radical coupling (ATNRC) chemistry followed by selective hydrolysis of poly(tert-butyl acrylate) backbone. A new Br-containing acrylate monomer, tert-butyl 2-((2-bromopropanoyloxy)methyl) acrylate, was first prepared, and it call be polymerized via RAFT in a controlled way to obtain a well-defined homopolymer with narrow molecular weight distribution (M-w/M-n = 1.06). Grafting-onto strategy was employed to synthesize PtBA-g-PPO well-defined graft copolymers with narrow molecular weight distributions (M-w/M-n = 1.05-1.23) via ATNRC reaction between Br-containing PtBA-based backbone and poly(propylene oxide) with 2,2,6, 6-tetramethylpiperidine-1-oxyl (TEMPO) end group using CuBr/PMDETA or Cu/PMDETA as catalytic system, The final PAA-g-PPO amphiphilic graft copolymers were obtained by the selective acidic hydrolysis of PtBA backbone in acidic environment without affecting the side chains. The critical micelle concentrations in aqueous media were determined by a fluorescence probe technique. Diverse micellar morphologies were formed with varying the content of hydrophobic PPO segment.