A PHEA-g-PEO well-defined graft copolymer exhibiting the synchronous encapsulation of both hydrophobic pyrene and hydrophilic Rhodamine 6G

A well-defined graft copolymer consisting of a poly(2-hydroxyethyl acrylate) (PHEA) backbone and poly(ethylene oxide) (PEO) side chains was synthesized by successive reversible addition-fragmentation chain transfer (RAFT) polymerization and atom transfer nitroxide radical coupling (ATNRC) reaction. RAFT homopolymerization of a Cl-containing acrylate monomer, 2-hydroxyethyl 2-((2-chloropropanoyloxy) methyl) acrylate (HECPMA), was first performed in a controlled way to afford a well-defined PHEA-based backbone with a low polydispersity (M-w/M-n = 1.08). The target poly(2-hydroxyethyl acrylate)-g-poly( ethylene oxide) (PHEA-g-PEO) graft copolymer with a narrow molecular weight distribution (M-w/M-n = 1.16) was then obtained by ATNRC reaction between the pendant -OCOCH(CH3)Cl group in every repeated unit of PHEA-based backbone and PEO with a TEMPO end group via the grafting-onto strategy, using CuCl/PMDETA as a catalytic system. The critical micelle concentrations (cmcs) of the obtained graft copolymer in pure water, brine, and aqueous Na2SO4 solution were determined by the fluorescence probe technique using N-phenyl-1-naphthylamine as probe and micellar morphologies in aqueous media were visualized by TEM. It was found that PHEA-g-PEO graft copolymer self-assembled into large compound micelles in aqueous media, which can encapsulate hydrophilic Rhodamine 6G and hydrophobic pyrene separately or simultaneously.