Synthesis and characterization of graft copolymers by photoinduced CuAAC click chemistry

Abstract

Well-defined graft copolymers were synthesized by a simple photoinduced copper(I) catalyzed 1,3-dipolar cycloaddition click reaction of alkyne-terminated poly(epsilon-caprolactone) (PCL) either side-chain azide-functional polystyrene (PSt) or poly(vinyl chloride) (PVC). The alkyne-terminated PCL was prepared by ring-opening polymerization of epsilon-caprolactone in bulk using Sn(Oct)2 as a catalyst and propargyl alcohol as an initiator. Whereas, the halide groups of PVC and poly(styrene-co-chloromethylstyrene) prepared by nitroxide mediated radical copolymerization were transformed to side chain azide-functional PVC or PSt via nucleophilic substitution reaction using sodium azide. Subsequently, the resulting alkyne and azide functional polymers were mixed in DMF with Cu(II)Br2/PMDETA ligand and 2, 2-dimethoxy-2-phenyl acetophenone and irradiated by UV light to form corresponding graft copolymers. The FT-IR, 1H NMR, GPC and DSC analyzes clearly pointed out an efficient photoinduced CuAAC click reactions between azide- and alkyne-functional precursor polymers.