Biodegradable and biocompatible PCL-g-PEG amphiphilic graft copolymers were prepared by combination of ROP and click chemistry via graft onto method under mild conditions. First, chloro-functionalized poly(e-caprolactone) (PCL-Cl) was synthesized by the ring-opening copolymerization of e-caprolactone (CL) and a-chloro-e-caprolactone (CCL) employing scandium triflate as high-efficient catalyst with near 100% monomer conversion. Second, the chloro groups of PCL-Cl were quantitatively converted into azide form by NaN3. Finally, copper(I)-catalyzed cycloaddition reaction was carried out between azide-functionalized PCL (PCL-N3) and alkyne-terminated poly(ethylene glycol) (A-PEG) to give PCL-g-PEG amphiphilic graft copolymers. The composition and the graft architecture of the copolymers were characterized by 1H NMR, FTIR, and GPC analyses. These amphiphilic graft copolymers could self-assemble into sphere-like aggregates in aqueous solution with diverse diameters, which decreased with the increasing of grafting density. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012