Synthesis of photoresponsive liquid crystal elastomers: a general chemical approach†

Abstract

Liquid crystal elastomers represent a versatile class of polymer materials with potential applications in soft robotics, adhesives, and smart materials. The integration of photoresponsive molecules into LCEs enables spatiotemporal control, wavelength-selective actuation and remote operations, expanding their application space. However, the incorporation of sensitive photoresponsive molecules is often hindered by the chemical methods and processing conditions required for the LCE fabrication. In this work, we introduce a general strategy for covalent incorporation of photoresponsive moieties into LCEs through Diels–Alder chemistry utilizing late-stage functionalization. This approach facilitates the retention of material alignment and thermomechanical properties, while enabling the functionalization of thick, aligned polysiloxane elastomers. A wide range of photoresponsive molecules, including azobenzenes, spiropyrans, cyanine dyes, and donor–acceptor Stenhouse adducts, were successfully integrated, demonstrating this method's versatility. Furthermore, we leverage the reversible nature of Diels–Alder conjugation to achieve on-demand editing and exchange of photoresponsive moieties within a single LCE, allowing for dynamic tuning of material properties. This platform offers a scalable and efficient route for developing multifunctional LCEs, providing new opportunities for advanced stimuli-responsive materials and broadening the scope of applications across various fields.