Reprogrammable, Reprocessible, and Self-Healable Liquid Crystal Elastomer with Exchangeable Disulfide Bonds.

A liquid crystal elastomer (LCE) can be regarded as an integration of mesogenic molecules into a polymer network. The LCE can generate large mechanical actuation when subjected to various external stimuli. Recently, it has been extensively explored to make artificial muscle and multifunctional devices. However, in the commonly adopted two-step crosslinking method for synthesizing monodomain LCEs, the LCE needs to be well-cross-linked in the first step before stretching, which increases the disorder of mesogenic molecules in the final state of the LCE and makes it very challenging to fabricate the LCE of complex shapes. In this article, we developed a new LCE with disulfide bonds, which can be reprogrammed from the polydomain state to the monodomain state either through heating or UV illumination, owing to the rearrangement of the polymer network induced by the metathesis reaction of disulfide bonds. In addition, the newly developed LCE can be easily reprocessed and self-healed by heating. Because of the excellent reprogrammability as well as reprocessability of the LCE, we further fabricated LCE-based active micropillar arrays through robust imprint lithography, which can be hardly achieved using the LCE prepared previously. Finally, we showed an excellent long-term durability of the newly developed LCE.