Constructing star polymersvia modular ligation strategies

Branched polymers result in a more compact structure in comparison to linear polymers of identical molecular weight, due to their high segment density which affects the crystalline, mechanical, and viscoelastic properties of the polymer. Star polymers constitute the simplest form of branched macromolecules where all of the chains—or arm segments—of one macromolecule are linked to a centre defined as the core. Over recent years, modular ligation reactions—some of which adhere to click criteria—have enabled the synthesis of a variety of star polymersvia efficient polymer–polymerconjugations. While the modified Huisgen [3 + 2] dipolar copper catalyzed azide and alkynecycloaddition (CuAAC) has been widely employed for macromolecular star synthesis, Diels–Alder and hetero Diels–Alder reactions offer alternative pathways which allow for similarly efficient macromolecular conjugations. Moreover, combinations of these protocols afford the synthesis of more complex star polymer structures which previously had not been achievable.