Smart Ionic Liquid Nanogel Actuators by Phototrigger for Efficient Extraction of Natural Active Ingredients from Biomass and Rapid Oil–Water Separation

Abstract

Designing smart molecular nanogels and nanogel actuators that can intelligently change the surface activity and controllably adjust the nanogel molecular arrangement has been a major challenge in the field of smart materials. Here, a series of ionic liquids composed of imidazolium ionic headgroups, alkyl chain spacers, and a photoresponsive azobenzene unit were designed. They can form smart ionic liquid nanogels with low melting points and construct smart nanogel actuators by light-trigger. The intelligent ionic liquid nanogels can be used to construct stable oil–water smart emulsions with photocontrollable actuators, which have the ability of reversible emulsification and demulsification triggered by light. The intelligent emulsions are applied to efficiently extract cinnamon oil from biomass cinnamon bark by a solvothermal method at low temperature. Cinnamaldehyde can be efficiently separated using intelligent reversible demulsification by the photocontrollable actuator. Cinnamaldehyde with a high purity of 97.21% can be obtained by the smart nanogel actuator. In a single extraction, the distributions of the smart ionic liquid in the water phase, the oil phase, and the cinnamon phase are 0.99%, 8.19%, and 90.82%, respectively. The total recovery rate of the smart ionic liquid is 95.53%. After three cycles, the extraction rate of cinnamon remains at 92.67%. 2D correlation FTIR spectra, 1 H NMR, and DFT calculations indicate that the constructed ionic liquid nanogels have strong supramolecular interaction with lignin macromolecules, the special ability to disassemble hydrogen bonds on lignin, and the ability to quickly swell lignin fibers. The smart ionic liquid nanogel actuator provides an advanced platform for efficient extraction of sensitive compounds and smart oil–water separation.

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