A series of palmitoyl chloride-grafted hyperbranched polyglycerols were synthesized through cationic ring-opening polymerization and end-group modification. The obtained grafted copolymer of HPG-C16 possesses a hydrophilic hyperbranched polyether core and many hydrophobic alkyl arms, which shows interesting self-assembly behavior in THF and water. The results indicate that the copolymers with a relatively high alkyl grafting ratio can form unimolecular micelles in THF and will further assemble into giant vesicles around 1-10 mu m in THF/water mixed solvents. However, the HPG-C16 with a low alkyl grafting ratio of 15.6% can directly assemble into vesicles in THF and form micelles in water. (C) 2009 Elsevier Inc. All rights reserved.