Rejuvenating liquid crystal elastomers for self-growth.

Abstract

To date, only one polymer can self-grow to an extended length beyond its original size at room temperature without external stimuli or energy input. This breakthrough paves the way for significant advancements in untethered autonomous soft robotics, eliminating the need for the energy input or external stimuli required by all existing soft robotics systems. However, only freshly prepared samples in an initial state can self-grow, while non-fresh ones cannot. The necessity of synthesizing from monomers for each use imposes significant limitations on practical applications. Here, we propose a strategy to rejuvenate non-fresh samples to their initial state for on-demand self-growth through the synergistic effects of solvents and dynamic covalent bonds during swelling. The solvent used for swelling physically transforms the non-fresh LCEs from the liquid crystal phase to the isotropic phase. Simultaneously, the introduction of the transesterification catalyst through swelling facilitates topological rearrangements through exchange reactions of dynamic covalent bonds. The rejuvenation process can also erase growth history, be repeated several times, and be regulated by selective swelling. This strategy provides a post-modulation method for the rejuvenation and reuse of self-growing LCEs, promising to offer high-performance materials for cutting-edge soft growing robotics.