Ethyl cellulose graft poly(poly(ethylene glycol) methyl ether methacrylate) (EC-g-P(PEGMA)) amphiphilic copolymers were synthesized via atom transfer radical polymerization (ATRP) and characterized by FTIR, H-1 NMR, and gel permeation chromatography. Reaction kinetics analysis indicated that the graft copolymerization is living and controllable. The self-assembly and thermosensitive property of the obtained EC-g-P(PEGMA) amphiphilic copolymers in water were investigated by dynamic light scattering, transmission electron microscopy, and transmittance. It was found that the EC-g-P(PEGMA) amphiphilic copolymers can self-assemble into spherical micelles in water. The size of the micelles increases with the increase of the side chain length. The spherical micelles show thermosensitive properties with a lower critical solution temperature around 65 degrees C, which almost independent on the graft density and the length of the side chains. The obtained EC-g-P(PEGMA) graft copolymers have both the unique properties of poly(ethylene glycol) and cellulose, which may have the potential applications in biomedicine and biotechnology. (c) 2008 Wiley Periodicals, Inc.