Near-infrared light-driven liquid crystalline elastomers with simultaneously enhanced actuation strain and stress

Liquid crystalline elastomers (LCEs) have attracted considerable attention in applications involving advanced soft actuators and robots. Emerging LCEs with high actuation stresses and actuation strains are desirable for practical applications. However, it is a common sense that improvements in the specific mechanical properties of LCEs must come at the expense of other features. In this work, an LCE material was prepared by a simple thiol-acrylate reaction followed by light-initiated radical polymerization. By adjusting the content of pendant liquid crystal (LC) mesogens, the crosslinking density of the LC network was regulated, and the actuation of the LCE was optimized. Introduction of the pendant LC mesogens reduced the actuation temperature and improved the actuation strain, while the acrylate-functionalized MXene nanosheets crosslinked the LCE matrix, ensuring high actuation stress and photothermal conversion. As a result, this work simultaneously enhanced the actuation stress and actuation strain of the LCE by introducing pendant LC mesogens and MXene nanosheets as cross-linkers, which avoided the limitations of previous LCE actuators, such as actuation by high temperature or harmful ultraviolet light, and physical doping-induced molecular disturbances. This greatly improved the overall actuation performance (the actuation stress was 0.773 MPa, and the actuation strain was 45%) and realized reversible deformation (54%) under near-infrared light. This strategy might provide a new way to optimize the capabilities of LCE actuators.