A well-defined amphiphilic copolymer of -poly(ethylene oxide) (PEO) linked with comb-shaped [poly(styrene-co-2-hydeoxyethyl methacrylate)-graft-poly(C.-caprolactone)] (PEO-b-P(St-co-HEMA)-g-PCL) was successfully synthesized by combination of reversible addition-fragmentation chain transfer polymerization (RAFT) with ring-opening anionic polymerization and coordination-insertion ring-opening polymerization (ROP). The a-methoxy poly(ethylene oxide) (mPEO) with omega,3-benzylsulfanylthiocarbonylsufanylpropionic acid (BSPA) end group (mPEO-BSPA) was prepared by the reaction of mPEO with 3-benzylsulfanylthiocarbonylsufanyl propionic acid chloride (BSPAC), and the reaction efficiency was close to 100%; then the mPEO-BSPA was used as a macro-RAFT agent for the copolymerization of styrene (St) and 2-hydroxyethyl methacrylate (HEMA) using 2,2-azobisisobutyronitrile as initiator. The molecular weight of copolymer PEO-b-P(St-co-HEMA) increased with the monomer conversion, but the molecular weight distribution was a little wide. The influence of molecular weight of macro-RAFT agent on the polymerization procedure was discussed. The ROP of epsilon-caprolactone was then completed by initiation of hydroxyl groups of the PEO-b-P(St-co-HEMA) precursors in the presence of stannous octoate (Sn(Oct)(2)). Thus, the amphiphilic copolymer of linear PEO linked with comb-like P(St-co-HEMA)-g-PCL was obtained. The final and intermediate products were characterized in detail by NMR, GPC, and UV. (c) 2005 Wiley Periodicals, Me.