Photoinduced, Swift, and Reversible Spatiotemporal Programming of Double Dynamically Bonded Liquid Crystal Elastomer Actuators.

Spatiotemporal programming of the morphing behavior of liquid crystal elastomers (LCEs) by local tailoring of the nematic to isotropic temperature (TNI) can empower the precise design of their versatile motions. The current approach and materials design to achieve this process are either slow or irreversible, limiting its efficiency and efficacy. Here, a dynamic bond of anthracene and ethyl acrylate (An-A) is introduced to enable photoinduced topology transformation to alter the TNI of the LCE, into a hydrogen-bonded supramolecular LCE network, where the actuation modes can already be reconfigured upon annealing. Experiments and molecular dynamics simulation demonstrate that the An-A bonds undergo reversible cycloaddition with 365 nm UV exposure for as short as 10 min, and depolymerization with 254 nm UV. The resulting topological transformations of the network give rise to changes in the TNI, actuation strain, and mechanical properties, which can be programed and erased by light. With that, a spatiotemporally reprogrammable LCE actuator: a single LCE that morphs into different shapes, especially those that are far more achievable when the trajectory can be designed by sequential actuation, is developed. This system offers a promising strategy for swift and reversible morphing behavior with custom-designed trajectory in future smart soft robots.