Synthesis of H-shaped complex macromolecular structures by combination of atom transfer radical polymerization, photoinduced radical coupling, ring-opening polymerization, and iniferter processes

Abstract

Three controlled/living polymerization processes, namely atom transfer radical polymerization (ATRP), ring opening polymerization (ROP) and iniferter polymerization, and photoinduced radical coupling reaction were combined for the preparation of ABCBD-type H-shaped complex copolymer. First, a-benzophenone functional polystyrene (BP-PS) and poly( methyl methacrylate) (BP-PMMA) were prepared independently by ATRP. The resulting polymers were irradiated to form ketyl radicals by hydrogen abstraction of the excited benzophenone moieties present at each chain end. Coupling of these radicals resulted in the formation of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) with benzpinacole structure at the junction point possessing both hydroxyl and iniferter functionalities. ROP of e-caprolactone (CL) by using PS-b-PMMA as bifunctional initiator, in the presence of stannous octoate yielded the corresponding tetrablock copolymer, PCL-PSPMMA- PCL. Finally, the polymerization of tert-butyl acrylate (tBA) via iniferter process gave the targeted H-shaped block copolymer