A series of well-defined double hydrophilic graft copolymers containing poly[poly(ethylene glycol) methyl ether acrylatel (PPEGMEA) backbone and poly[poly(ethylene glycol) ethyl ether methacrylatel (PPEGEEMA) side chains were synthesized by the combination of single electron transfer-living radical polymerization (SET-LRP) and atom transfer radical polymerization (ATRP). The backbone was first prepared by SET-LRP of poly(ethylene glycol) methyl ether acrylate macromonomer using CuBr/tris(2-(dimethylamino)ethyl)amine as catalytic system. The obtained comb copolymer was treated with lithium diisopropylamide and 2-bromoisobutyryl bromide to give PPEGMEA-Br macroinitiator. Finally, PPEGMEA-g-PPEGEEMA graft copolymers were synthesized by ATRP of poly(ethylene glycol) ethyl ether methacrylate macromonomer using PPEGMEA-Br macroinitiator via the grafting-from route. The molecular weights of both the backbone and the side chains were controllable and the molecular weight distributions kept narrow (M-w/M-n <= 1.20). This kind of double hydrophilic copolymer was found to be stimuli-responsive to both temperature and ion (0.3 M Cl- and SO42-). (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 647-655, 2010