Visible-Light-Driven and Adaptable Liquid-Crystalline Elastomer Actuators Containing Dynamically Exchangeable Boron Ester and Disulfide Linkages

초록

A liquid-crystalline elastomer (LCE) containing dynamically exchangeable disulfide (-S-S-) and boron ester (BE) bonds (LCESS-BE) was successfully prepared. The -S-S- linkages were introduced in the form of a reactive oligomer prepared via a thiol-acrylate Michael addition reaction with bis(2-hydroxyethyl) disulfide acrylate, while the BE linkages were incorporated via the visible-light-induced cross-linking of the oligomer with 4-((allyloxy)methyl)-2-(4-vinylphenyl)-1,3,2-dioxaborolane (AMVD). The monodomain LCESS-BE (MLCESS-BE) with similar to 1 wt % AMVD promoted photothermal actuation under blue-light irradiation, resulting in a rise in its temperature of similar to 147 degrees C and a decrease in its length of similar to 42%. In addition, LCESS-BE films exhibited reversible reprogrammability through two dynamic exchange reactions (DERs) involving either BE or -S-S- linkages. The BE linkages induced water-assisted healing through a hydration/dehydration DER under ambient conditions via a glue-free method, while the -S-S- linkages exhibited a UV-light-induced DER below the nematic-to-isotropic transition temperature, thus maintaining the nematic order during the DER. This approach represents a promising method for the preparation of MLCEs with light-induced actuation and multifunctionality involving reprogramming, reprocessing, and healing properties.

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