Constructing well-defined star graft copolymers

This review highlights representative efforts to construct well-defined star graft copolymers over the past decade. Star graft copolymers, consisting of multiple arms connected to a central core as the backbone, and branched side chains grafted from the arms, possess a more complex topological architecture than traditional graft copolymers and star polymers bearing linear arms. According to the distinction of grafting density, star graft copolymers can be divided into typical star graft copolymers with loosely grafted side chains, and star brush polymers with densely grafted side chains. For the synthesis of both types, there are great difficulties in achieving precise control over their topology, microstructure, and composition. Especially for the preparation of star brush polymers, their high grafting densities and steric hindrance also bring more challenges. Through the combination of two tactics for preparing star polymers, the diverse strategies employed in synthesizing graft copolymers, and a great variety of controlled/living polymerization techniques, a series of star graft polymers has been obtained. Thanks to the giant size and high compactness of star brush polymers, the unique hierarchical self-organization behavior of these highly branched star polymers will pave the way for their potential use in the fields of drug delivery, bio-catalysis, super soft elastomers, and templates for hybrid nanomaterials, acting as unimolecular micelles.