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(ε-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, Iω-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, ε-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 ¹H NMR, FTIR, and GPC measurements.