Liquid Crystal Elastomers Prepared by Thiol–Ene Photopolymerization Amenable to Surface-Enforced Alignment

Liquid crystal elastomers (LCEs) assimilate the anisotropy of liquid crystalline phases with the rubber elasticity of polymer networks. Numerous recent reports detail the preparation of LCEs by sequential chain extension reactions of diacrylate liquid crystalline monomers followed by the photopolymerization of liquid crystalline oligomers. While these reactions are widely utilized, sample fabrication can take hours or even days. Other reports detail the preparation of LCEs via direct thiol–acrylate photopolymerization via free radical chain transfer reactions. While this is a rapid and straightforward approach to preparing LCEs, the topology of the polymer network composition is heterogeneous, with wide variance in molecular weight between cross-links and extensive prevalence of pendant groups. Here, we detail the preparation of LCEs via thiol–ene photopolymerization. The compositions introduced here are amenable to surface-enforced alignment, which enables the high-fidelity inscription of complex director profiles. Compared to prior thiol-based LCE compositions, direct preparation of LCE by thiol–ene photopolymerization is rapid, forms largely homogeneous polymer networks, and has wide tunability in cross-link density.