Synthesis and characterizations of well-defined branched polymers with AB(2) branches by combination of RAFT polymerization and ROP as well as ATRP

摘要

A well-defined branched copolymer with PLLA-b-PS2 branches was prepared by combination of reversible addition-fragmentation transfer (RAFT) polymerization, ring-opening polymerization (ROP), and atom transfer radical polymerization (ATRP). The RAFT copolymerization of methyl acrylate (MA) and hydroxyethyl acrylate (HEA) yielded poly(MA-co-HEA), which was used as macro initiator in the successive ROP polymerization of LLA. After divergent reaction of poly(MA-co-HEA)-g-PLLAOH with divergent agent, the macro initiator, poly(MA-co-HEA)-g-PLLABr(2) was formed in high conversion. The following ATRP of styrene (St) produced the target polymer, poly(MA-co-HEA)-g-(PLLA-b-PS2). The structures, molecular weight, and molecular weight distribution of the intermediates and the target polymers obtained from every step were confirmed by their H-1 NMR and GPC measurements. DSC results show one T-g(copolymer) = 3 degrees C for the poly(MA-co-HEA), T-g(copolymer) = -5 degrees C, T-c(PLLA)= 122 degrees C, and T-m(PLLA) =157 degrees C for the branched copolymers (poly(MA-co-HEA)-g-PLLA), and T-g(PS) = 51 degrees C, T-c(PLLA) = 116 degrees C, and T-m(PLLA) = 162 degrees C for poly(MA-co-HEA)-g-(PLLA-b-PS2). (c) 2005 Wiley Periodicals, Inc.