含可交换动态共价键的液晶聚合物驱动器

Liquid Crystalline Polymer Actuators with Exchangeable Dynamic Covalent Bonds

液晶聚合物网络(liquid crystalline polymer networks,LCNs)是一类同时具备高分子网络的熵弹性和液晶有序性的聚合物材料.取向后的单畴LCNs在特定外界刺激下可以产生快速的宏观大形变,作为驱动器和传感器,在人工肌肉、柔性机器人和微机械体系等领域具有广阔的应用前景.近年来,研究者开发了一种新型的将可交换动态共价键引入LCNs制备可逆形变驱动器的方法.相比于传统制备方法,该方法不仅是全新的LCNs取向方法,而且赋予了材料一些传统永久交联LCNs不具备的新功能.本文介绍了近年来研究者在含可交换动态共价键的LCNs驱动器方向的重要研究成果,突出介绍了本课题组在含动态共价键的LCNs驱动器方向的研究进展.最后,对含可交换动态共价键的LCNs驱动器未来面临的挑战及发展方向进行了展望.

Recently,polymer soft actuators have attracted massive attention among researchers.Owing to their unique features like light weight,low costs,and flexible actuations,polymer soft actuators are considered to be ideal candidates for the advanced high-tech fields such as micromechanical systems,artificial muscles,and soft robotics.Liquid crystalline polymer networks(LCNs)possess both the anisotropy property of liquid crystals and the entropy elasticity of polymer networks,standing out among the numerous reported polymer soft actuators.The most attractive property of LCNs is the reversible rapid macroscopic deformation(due to transition from isotropy to anisotropy),which requires macroscopic orientation of liquid-crystal order.Since traditional LCNs are covalently cross-linked networks which cannot be reprocessed once synthesized(thermosets),the aligning before the complete curing is inevitable.In the past decades,various methods and techniques have been developed for the orientation order of LCNs,including two-step crosslinking method,external fields,in situ photoalignment,inkjet printing,soft lithography,and microfluidics.Although many progresses have been achieved,they still suffer from some inborn disadvantages such as delicate procedures,limited size,and especially the difficulty to obtain complex 3 D shapes,which greatly restricted the practical applications of LCN actuators.In recent years,a novel method has been developed for preparation of LCN actuators by introducing exchangeable dynamic covalent bonds into LCNs.Owing to the exchange reactions,the orientation order could be obtained by stretching the wellcured LCNs under specific external stimuli.Compared with the traditional preparation methods,this strategy not only brings a totally new,simple,and reliable method for LCNs orientation,but also endows these materials with some brand-new functions that traditional permanent cross-linked LCNs do not possess,including easy fabrication of complex 3 D structures,reprogramming,multi-shape memory,and self-healing.This review introduces the important research progress in the area of LCN actuators containing exchangeable dynamic covalent bonds in recent years,and highlights the research progress of our group.Finally,the future challenges and development directions of LCN actuators containing exchangeable dynamic covalent bonds are prospected.