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 bycombining two photochemical strategies, namely photoinduced atom transfer radicalpolymerization (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 asimple substitution of the chain end halides. Parallel to this, the alkyne-PCL was synthesized byring opening polymerization of ε-caprolactone, employing propargyl alcohol as initiator. For thesynthesis of alkyne-PEG, industrially available PEG was functionalized by a simple esterificationreaction using 5-pentynoic acid. After the syntheses of these alkyne functional polymers asclickable counterparts, they were reacted with N3-PS-N3 by photoinduced click reactions toprepare the desired triblock copolymers. All polymers were characterized by NMR, FTIR, andGPC analyses.