Preparation and characterization of heteroarm H‐shaped terpolymers by combination of reversible addition‐fragmentation transfer polymerization and ring‐opening polymerization

Heteroarm H‐shaped terpolymers, [(poly(L‐lactide))(polystyrene)]poly(ethylene oxide)[(polystyrene)(poly(L‐lactide))], [(PLLA)(PS)]PEO[(PS)(PLLA)], in which PEO acts as a main chain and PS and PLLA as side arms, have been successfully prepared via combination of reversible addition–fragmentation transfer (RAFT) polymerization and ring‐opening polymerization (ROP). The first step is the synthesis of the PEO capped with one terminal dithiobenzoate group and one hydroxyl group at every chain end, [(HOCH2)(PhC(S)S)]PEO[(S(S)CPh)(CH2OH)] from the reaction of carboxylic acid with ethylene oxide. Then, the RAFT polymerization of styrene (St) was carried out using [(HOCH2)(PhC(S)S)]PEO[(S(S)CPh)(CH2OH)] as RAFT agent and AIBN as initiator, and the triblock copolymer, [(HOCH2)(PS)]PEO[(PS)(CH2OH)], was formed. Finally, the heteroarm H‐shaped terpolymers, [(PLLA)(PS)]PEO[(PS)(PLLA)], were produced by ROP of LLA, using triblock copolymer, [(HOCH2)(PS)]PEO[(PS)(CH2OH)], as macroinitiator and Sn(Oct)2 as catalyst. The target products and intermediates were characterized by 1H NMR spectroscopy and gel permeation chromatography.