Synthesis of photoresponsive liquid crystal elastomers: A general chemical approach

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.