Synthesis of ABCD 4-miktoarm star polymers by combination of RAFT, ROP, and "Click chemistry"'

The ABCD 4-miktoarm star polymers based on polystyrene (PS), poly(e-caprolactone) (PCL), poly(methyl acrylate) (PMA), and poly(ethylene oxide) (PEO) were synthesized and characterized successfully. Using the mechanism transformation strategy, PS with three different functional groups (i.e., hydroxyl, alkyne, and trithiocarbonate), PS-HEPPA-SC(S)SC12H25, was synthesized by the reaction of the trithiocarbonate-terminated PS with 2-hydroxyethyl-3-(4-(prop-2-ynyloxy)phenyl) acrylate (HEPPA) in tetrahydrofuran (THF) solution. Subsequently, the ring-opening polymerization (ROP) of epsilon-caprolactone (CL) was carried out in the presence of stannous(II) 2-ethylhexanoate and PS-HEPPA-SC(S)SC12H25, and then the PS-HEPPA(PCL)-SC(S)SC12H25 obtained was used in reversible addition-fragmentation chain transfer (RAFT) polymerization of methyl acrylate (MA) to produce the ABC 3-miktoarm star polymer, S(PS)(PCL)(PMA) carrying an alkyne group. The ABCD 4-miktoarm star polymer, S(PS)(PCL)(PM)(PEO) was successfully prepared by click reaction of the alkyne group on the HEPPA unit with azide-terminated PEO (PEO-N-3). The target polymer and intermediates were characterized by NMR, FTIR, GPC, and DSC. (C) 2008 Wiley Periodicals, Inc.