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

Brush-type, amphiphilic [poly(styrene-co-2-hydroxyethyl methacrylate)-graft-poly(ε-caprolactone)]-6-poly(ethylene oxide)-b-[poly(styrene-co-2-hydroxyethyl methacrylate)-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.