Star polymer networks: a toolbox for cross-linked polymers with controlled structure

The synthesis of precisely controlled polymer networks has been a long-cherished dream of polymer scientists. Traditional random cross-linking strategies often lead to uncontrolled networks with various kinds of defects. Recent advances in polymer synthesis have yielded a concept that could solve these problems, namely, star polymer networks. Polymer networks constructed by end-linking multiarm polymers with a narrow molecular weight distribution have been shown to be much more homogeneous than the conventional networks. Thus, this type of polymer network has been employed as a convenient tool in various fields, from exploration of fundamental physics of polymer networks to development of functional soft materials. For efficient use of this strategy, the user needs to be familiar with two key elements: the end-linking reaction and the type of polymer. Here, we comprehensively review the chemistries of star polymer networks, with particular focus on these two points.