Block and star block copolymers by mechanism transformation 9: Preparation and characterization of poly(methyl methacrylate)/poly(1,3‐dioxepane)/polystyrene ABC miktoarm star copolymers by combination of reversible addition–fragmentation chain‐transfer polymerization and cationic ring‐opening polymerization

The miktoarm ABC star copolymer with three different branches, polystyrene (PS), poly(1,3‐dioxepane) (PDOP), and poly(methyl methacrylate) (PMMA), was successfully prepared. PS with two transfer groups, hydroxyl and dithiobenzoate groups PS‐HECA‐SC(S)Ph], was synthesized by the reaction of a dithiobenzoate group at the end of PS with hydroxyethylene cinnamate (HECA) in tetrahydrofuran solution. Then, the cationic ring‐opening polymerization of 1,3‐dioxepane was initiated by triflic acid in the presence of PS‐HECA‐SC(S)Ph and diblock copolymer, PS‐PDOP, was formed. Finally, the diblock copolymer with the dithiobenzoate group situated between the two blocks was used in the reversible addition–fragmentation transfer (RAFT) process of methyl methacrylate (MMA). The miktoarm ABC star copolymer S(PS)(PDOP)(PMMA) was characterized by ¹H NMR spectroscopy and gel permeation chromatography. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1243–1250, 2003