Synthesis of well‐defined, brush‐type, amphiphilic [poly(styrene‐co‐2‐hydroxyethyl methacrylate)‐graft‐poly(ε‐caprolactone)]‐b‐poly(ethylene oxide)‐b‐[poly(styrene‐co‐2‐hydroxyethyl methacrylate)‐graft‐poly(ε‐caprolactone)] and its aggregation behavior inaqueous media

Abstract

AbstractBrush‐type, amphiphilic [poly(styrene‐co‐2‐hydroxyethyl methacrylate)‐graft‐poly(ε‐caprolactone)]‐b‐poly(ethylene oxide)‐b‐[poly(styrene‐co‐2‐hydroxyethylmethacrylate)‐graft‐poly(ε‐caprolactone)] was successfully synthesized via consecutive ring‐opening anionic polymerization, reversible addition–fragmentation chain transfer (RAFT) polymerization, and coordination–insertion ring‐opening polymerization (ROP). Two poly (ethylene oxide) macro‐RAFT agents with two 3‐benzylsulfanylthiocarbonylsufanyl propionic acid end groups were prepared by the reaction of Poly(ethylene oxide) with hydroxyl group at two ends [HO–PEO–OH] with 3‐benzylsulfanylthiocarbonylsufanyl propionic acid chloride in the presence of pyridine; their molecular weights were 4840 and 8570 g/mol, and their molecular weight distributions were 1.07 and 1.09, respectively. The obtained macro‐RAFT agents were used to mediate the copolymerization of styrene and 2‐hydroxyethyl methacrylate with 2,2‐azobisisobutyronitrile as the initiator and dimethylformamide as the solvent. The hydroxyl groups of the 2‐hydroxyethyl methacrylate units of the resulting triblock copolymers then initiated the ROP of ε‐caprolactone in the presence of Sn(Oct)2 at 100 °C in toluene. It was determined that the RAFT process was controllable. The self‐assembled morphologies of the copolymers varied from rods to pearl necklaces and vesicles with an increase in the water concentration in tetrahydrofuran from 22.0 to 25.7, 29.6, and 39.0%, and the morphologies were also dependent on the molecular weight and chain structure of the copolymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4396–4408, 2006