Abstract
A series of well-defined amphiphilic graft copolymer bearing a hydrophilic poly(2-hydroxyethyl acrylate) (PHEA) backbone and hydrophobic poly(methyl methacrylate) (PMMA) side chains was synthesized by successive reversible addition-fragmentation chain transfer (RAFT) polymerization and atom transfer radical polymerization (ATRP) through the grafting-from strategy. A well-defined PHEA-based backbone with Cl-containing ATRP initiating group in every repeated unit (Mw/Mn = 1.08), poly(2-hydroxyethyl 2-((2-chloropropanoyloxy)methyl)acrylate) (PHECPMA), was first prepared by RAFT homopolymerization of 2-hydroxyethyl 2-((2-chloropropanoyloxy)methyl)acrylate (HECPMA), a Cl-containing trifunctional acrylate. ATRP of methyl methacrylate was subsequently initiated by PHECPMA homopolymer to afford the target well-defined poly(2-hydroxyethyl acrylate)-graft-poly(methyl methacrylate) (PHEA-g-PMMA) graft copolymers (Mw/Mn ≤ 1.36) with 34 PMMA side chains and 34 pendant hydroxyls in PHEA backbone using CuCl/dHbpy as catalytic system. The critical micelle concentration (cmc) of the obtained graft copolymer was determined by fluorescence spectroscopy using N-phenyl-1-naphthylamine as probe while micellar morphologies in aqueous media were visualized by transmission electron microscopy. Interestingly, PHEA-g-PMMA graft copolymer could self-assemble into large compound micelles rather than common spherical micelles, which can encapsulate hydrophilic rhodamine 6 G and hydrophobic pyrene separately or simultaneously.
Highlights
Studies on graft copolymers have been restricted because the synthesis of well-defined graft copolymers with controlled molecular weights and narrow molecular weight distributions is a much tougher task www.nature.com/scientificreports/
The most popular grafting-from approach can be employed in the present work to construct the well-defined amphiphilic graft copolymer consisting of hydrophilic Poly(2-hydroxyethyl acrylate) (PHEA) backbone and hydrophobic poly(methyl methacrylate) (PMMA) side chains through reversible-deactivation radical polymerization (RDRP) of MMA initiated by the corresponding pendant initiating groups in the backbone
hydroxyethyl 2-((2-chloropropanoyloxy)methyl)acrylate (HECPMA) monomer[19] comprising a polymerizable double bond, a -OCOCH(CH3)Cl atom transfer radical polymerization (ATRP) initiating group, and a hydroxyl was employed as starting material in the current work to construct PHEA-g-PMMA well-defined amphiphilic graft copolymer by successive RDRP via the grafting-from strategy
Summary
A series of well-defined amphiphilic graft copolymer bearing a hydrophilic poly(2-hydroxyethyl acrylate) (PHEA) backbone and hydrophobic poly(methyl methacrylate) (PMMA) side chains was synthesized by successive reversible addition-fragmentation chain transfer (RAFT) polymerization and atom transfer radical polymerization (ATRP) through the grafting-from strategy. The RDRP initiating groups on the backbone are able to initiate ATRP or SET-LRP to introduce the side chains without affecting the pendant hydroxyls[18,19], which means that amphiphilic graft copolymers with PHEA/PHEMA as the hydrophilic backbone can be obtained directly without the modification of the backbone. The cmc of PHEA-g-PMMA amphiphilic graft copolymer in aqueous media was measured by fluorescence spectroscopy and the micellar morphology was preliminarily explored using transmission electron microscopy (TEM)
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