(437d) 3D Printed Reconfigurable Liquid Crystal Elastomers Via Light-Triggered Dynamic-Covalent Bonds

3D printing (3DP) of liquid crystal elastomers (LCEs) enables programming of complex, fully reversible 3D shape changes. Classical LCEs must be continuously heated to maintain their programmed actuated shape; here, we demonstrate reconfigurable 3DP LCE architectures by incorporating dynamic-covalent bonds into the LCE backbone. These 3DP LCEs can ‘lock-in’ on demand to maintain their complex programmed actuated state via bond exchange. Specifically, we create a printable ink containing dynamic-covalent bonds by oligomerizing liquid crystal mesogens with an allyl dithiol chain extender. During printing, the ink is crosslinked to form a LCE that undergoes reversible programmed shape-change upon heating above its nematic-to-isotropic transition temperature, T_NI. We leverage light-activated bond exchange to ensure the ‘trigger’ for bond exchange is orthogonal to the temperature change required for actuation. These reconfigurable LCEs enable architectures to be realized that are inaccessible by printing other classes of soft materials. Finally, by integrating these bond-exchangeable LCEs with standard LCEs via multimaterial 3D printing, we demonstrate a path towards hierarchical, reconfigurable, and responsive structures.