First double hydrophilic graft copolymer bearing a poly(2-hydroxylethyl acrylate) backbone synthesized by sequential RAFT polymerization and SET-LRP

Abstract

Two well-defined double hydrophilic graft copolymers comprising a hydrophilic poly(2-hydroxyethyl acrylate) (PHEA) backbone and hydrophilic poly(N-isopropylacrylamide) (PNIPAM) side chains were synthesized by the combination of reversible addition–fragmentation chain transfer (RAFT) polymerization, single-electron-transfer living radical polymerization (SET-LRP), and a grafting-from strategy. A 2-hydroxyethyl 2-((2-chloropropanoyloxy)methyl)acrylate monomer containing an SET-LRP initiating group (–OCOCH(CH₃)Cl) was first RAFT homopolymerized to provide a PHEA-based homopolymer bearing a Cl-containing SET-LRP initiating group in every repeated unit with a narrow molecular weight distribution (M_w/M_n = 1.17). This homopolymer directly initiated SET-LRP of N-isopropylacrylamide at ambient temperature to afford the desired well-defined poly(2-hydroxyethyl acrylate)-graft-poly(N-isopropylacrylamide) graft copolymers (M_w/M_n ≤ 1.33) with hydroxyl in every repeated unit of the backbone without polymeric functionality transformation. The thermo-responsive phase behavior of the obtained double hydrophilic graft copolymers was investigated by UV/vis spectroscopy, ¹H NMR, and dynamic light scattering (DLS).