刚柔耦合液晶弹性体薄膜的力学性能及驱动行为研究

Study on mechanical property regulation and actuation behavior of rigid-flexible coupled liquid crystal elastomer films

  • 摘要: 液晶弹性体(LCE)兼具液晶各向异性与聚合物熵弹性,在软体机器人、仿生驱动器等柔性智能器件的快速发展的背景下备受关注。其驱动器面临的关键挑战在于如何平衡材料的力学性能与热致驱动行为。本文通过协同引入含动态碳氮双键(C=N)的刚性链与聚己内酯二醇(PCL)柔性链,构建了一种动态交联的刚柔耦合液晶弹性体薄膜(PCL-CN-LCE)。在柔性链PCL良好柔顺性以及刚性链CN的π-π堆积作用和偶极增强的协同下,PCL-CN-LCE薄膜的相转变温度被精准调控至50 ℃。动态C=N键的引入提高了液晶聚合物的交联密度,使薄膜的断裂拉伸强度达到6.1 MPa,拉伸率达到224.6%,驱动应变保持在36.8%,从而在不牺牲力学与驱动性能的前提下有效降低了驱动温度。进一步将PCL-CN-LCE薄膜与聚酰亚胺(PI)电热片组装,制备了一种电热驱动器。在5 V电压下,该驱动器实现了稳定的弯曲形变,弯曲角度达274.8°,并能在3秒内稳定抓取质量为2.7 g的乒乓球。本工作为动能型液晶弹性体的设计与应用提供了新思路。

     

    Abstract: Liquid crystal elastomers (LCEs), which combine the anisotropy of liquid crystals with the entropic elasticity of polymer networks, have attracted considerable attention owing to the rapid development of flexible intelligent devices such as soft robotics and bioinspired actuators. A major challenge in LCE-based actuators lies in balancing mechanical properties and thermally induced actuation behavior. In this study, a dynamically crosslinked liquid crystal elastomer film with a rigid-flexible coupled network (denoted as PCL-CN-LCE) was constructed through the synergistic incorporation of a rigid chain containing dynamic carbon-nitrogen double bonds (C=N) and a flexible polycaprolactone diol (PCL) chain. Leveraging the inherent flexibility of the PCL chain together with the π–π stacking interactions and dipole enhancement effects of the rigid CN chain, the phase transition temperature of the PCL-CN-LCE film was precisely tuned to 50 ℃. The introduction of dynamic C=N bonds increases the crosslinking density of the liquid crystal polymer, resulting in a fracture tensile strength of 6.1 MPa, an elongation at break of 224.6%, and a retained actuation strain of 36.8%. Consequently, the actuation temperature was effectively lowered without sacrificing mechanical or actuation performance. Furthermore, the PCL-CN-LCE film was assembled with a polyimide (PI) electrothermal sheet to fabricate an electrothermal actuator. At a driving voltage of 5 V, the actuator exhibited stable bending deformation with a bending angle of 274.8° and could reliably grasp a ping-pong ball weighing 2.7 g within 3 seconds. This work provides a new paradigm for the design and application of kinetic liquid crystal elastomers.

     

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