Multiple Controlled Graft Copolymers by Transition Metal-Catalyzed Living Radical Polymerization

This study is directed to the synthesis of a series of well-defined graft copolymers with the controlled lengths of both the backbone and graft chains by the ruthenium-catalysed living radical polymerisation. The backbone polymer was first synthesised by the ruthenium-catalysed living radical random copolymerisation of methyl methacrylate and 2-(trimethylsilyloxy)ethyl methacrylate followed by the in-situ transformation of the silyloxyl group into the ester with a C-Br bond, which resulted in efficient multifunctional macroinitiators for living radical graft copolymerisation. The methodology led to the novel controlled architectural copolymers, A_x-BA_x-type block-graft copolymers, which can function as new building blocks for controlled nanostructures based on microphase separation and is different from that of the conventional ABA triblock copolymers. A series of well-defined A_x-BA_x-type block-graft copolymers consisting of soft middle segments (dodecyl methacrylate) and hard outer graft chains (styrene) were synthesised by the ruthenium-catalysed block and graft polymerisations to exhibit characteristics of a thermoplastic elastomer.