ABC Type Miktoarm Star Copolymers Through Combination of Controlled Polymerization Techniques with Thiol-ene and Azide-Alkyne Click Reactions

ABC type miktoarm star copolymer with polystyrene (PS), poly(epsilon-caprolactone) (PCL) and poly(ethylene glycol) (PEG) arms was synthesized using controlled polymerization techniques in combination with thiol-ene and copper catalyzed azide-alyne click reactions (CuAAC) and characterized. For this purpose, 1-(allyloxy)-3-azidopropan-2-ol was synthesized as the core component in a one-step reaction with high yields (96%). Independently, x-thiol functionalized polystyrene (PS-SH) was synthesized in a two-step protocol with a very narrow molecular weight distribution. The bromo end function of PS obtained by atom transfer radical polymerization was first converted to xanthate function and then reacted with 1, 2-ethandithiol to yield desired thiol functional polymer (PS-SH). The obtained polymer was grafted onto the core by thiol-ene click chemistry. In the following stage, e-caprolactone monomer was polymerized from the core by ring opening polymerization (ROP) using tin octoate as catalyst through hydroxyl groups to form the second arm. Finally, PEG-acetylene, which was simply synthesized by the esterification of Me-PEG and 5-pentynoic acid, was clicked onto the core through azide groups present in the structure. The intermediates at various stages and the final miktoarm star copolymer were characterized by (1)H NMR, FTIR, and GPC measurements. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 24172422, 2011