Aqueous Phase Exfoliation of Two-Dimensional Materials Assisted by Thermoresponsive Polymeric Ionic Liquid and Their Applications in Stimuli-Responsive Hydrogels and Highly Thermally Conductive Films

With the increasing attention for various two-dimensional (2D) materials in recent years, developing a universal, facile, and eco-friendly method to exfoliate them into single- and few-layered nanosheets is becoming more and more urgent. Herein, we use a thermoresponsive polymeric ionic liquid (TRPIL) as a universal polymer surfactant to assist the high-efficiency exfoliation of molybdenum disulfide (MoS 2 ), graphite, and hexagonal boron nitride in an aqueous medium through consecutive sonication. In this case, the reliable interaction between 2D materials and the TRPIL would facilitate the exfoliation and simultaneously achieve a noncovalent functionalization of the exfoliated nanosheets. Interestingly, the dispersion stability of exfoliated nanosheet suspensions can be reversibly tuned by temperature because of the thermoresponsive phase transition behavior of the TRPIL. As a proof of potential applications, a temperature and photo-dual-responsive TRPIL/MoS 2 coloring hydrogel with robust mechanical property and an artificial nacre-like BN nanosheet film with high thermal conductivity were fabricated.