Combination of Photoinduced ATRP and Click Processes for the Synthesis of Triblock Copolymers

Abstract

ABA type triblock copolymers possessing polystyrene as middle segment and poly(ε-caprolactone) (PCL) and poly(ethylene glycol) (PEG) as side segments were synthesized by combining two photochemical strategies, namely photoinduced atom transfer radical polymerization (ATRP) and click processes. For this purpose, α,ω-diazido functional polystyrene (N₃-PS-N₃) was synthesized by photoinduced ATRP using a bifunctional initiator, followed by a simple substitution of the chain end halides. Parallel to this, alkyne-PCL was synthesized by ring opening polymerization of ε-caprolactone, employing propargyl alcohol as initiator. For the synthesis of alkyne-PEG, industrially available PEG was functionalized by a simple esterification reaction using 5-pentynoic acid. After the syntheses of these alkyne functional polymers as clickable counterparts, they were reacted with N₃-PS-N₃ by photoinduced click reactions to prepare the desired triblock copolymers. All polymers were characterized by NMR, IR and GPC analyses.

Keywords

• Atom transfer radical polymerization,Copper-catalyzed azide-alkyne cycloaddition,Photochemistry,block

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