Synthesis and thermoreversible gelation of coil-helical polyethylene-block-poly(γ-benzyl-L-glutamate) diblock copolymer

Well-defined coil-helical polyethylene-b-poly(gamma-benzyl-L-glutamate) diblock copolymers (PE-b-PBLG) were synthesized by a tandem synthetic strategy combining living polymerization of ethylene and ringopening polymerization of gamma-benzyl-L-glutamate-N-carboxyanhydride (BLG-NCA). Narrowly dispersed hydroxyl-terminated polyethylenes (PE-OH) with high branching density were synthesized by living polymerization of ethylene using an amine imine nickel catalyst and a transfer agent of ZnEt2 with high efficiency of >90%. Macroinitiator PE-NH2 could be quantitatively obtained by endcapping hydroxyl group of PE with N-tert-butoxycarbonyl-L-valine (BOC-L-valine) and deprotecting BOC group. PE-b-PBLG diblock copolymers were synthesized by subsequent ROP of BLG-NCA. These functional PE materials can form thermoreversible gels by self-assembled nanoribbons in toluene, which will expand the functionality and application of PE based materials. (C) 2013 Elsevier Ltd. All rights reserved.