Liquid crystalline elastomers based on click chemistry

Liquid crystalline elastomers (LCEs) have emergedas an important class of functional materials that are suitable for a wide range of applications, such as sensors, actuators, and softrobotics. The unique properties of LCEs originate from the combination between liquid crystal and elastomeric network. Thecontrol of macroscopic liquid crystalline orientation and networkstructure is crucial to realizing the useful functionalities of LCEs. Avariety of chemistries have been developed to fabricate LCEs,including hydrosilylation, free radical polymerization of acrylate,and polyaddition of epoxy and carboxylic acid. Over the past fewyears, the use of click chemistry has become a more robust andenergy-efficient way to construct LCEs with desired structures. This article provides an overview of emerging LCEs based on clickchemistries, including aza−Michael addition between amine and acrylate, radical-mediated thiol−ene and thiol−yne reactions, base-catalyzed thiol−acrylate and thiol−epoxy reactions, copper-catalyzed azide−alkyne cycloaddition, and Diels−Alder cycloaddition.The similarities and differences of these reactions are discussed, with particular attention focused on the strengths and limitations of each reaction for the preparation of LCEs with controlled structures and orientations. The compatibility of these reactions with thetraditional and emerging processing techniques, such as surface alignment and additive manufacturing, are surveyed. Finally, the challenges and opportunities of using click chemistry for the design of LCEs with advanced functionalities and applications are discussed