腰接型侧链液晶弹性体研究进展

液晶弹性体是交联型液晶大分子,兼具液晶取向有序性和交联聚合物熵弹性等特性,在传感器、触发器、微流体装置和仿生器件等方面具有很好的应用前景.制备液晶弹性体的微结构,探索其独特的刺激响应性,是目前液晶弹性体研究的重要方向.侧链液晶弹性体的液晶相态类型取决于其液晶基元和主链的连接方式.腰接型侧链液晶弹性体倾向于形成向列型液晶相,具有较快的响应速度和形变程度,是一类独特的液晶弹性体.本文重点介绍腰接型液晶弹性体微结构(如微米柱、微米线等)的制备;利用金纳米粒子的光热转换效应,实现液晶弹性体光响应性的新途径;以及腰接型侧链液晶弹性体仿生微结构的功能性等.同时还对该领域的发展前景进行了展望.

Recent Progresses in Side-on Liquid Crystalline Elastomers

This article highlights some recent progresses in side-on liquid crystalline elastomer (LCE) researches,including their preparation,functions and possible applications.LCEs are networks formed by lightly crosslinked liquid crystalline polymers,which show both liquid crystalline order of the mesogens and elasticity of the polymeric networks.Owing to their interesting properties,LCEs are highly competitive candidates as stimuli-responsive materials in sensors,actuators,microfluidics and biomimicking devices and other areas.Developing new microstructures and realizing better stimuli-responsive functions have drawn a wide range of attention in recent years.Side-on LCE is an important category of LCEs,in which mesogenic units are waist-connected to the backbone of a polymer,and the mesogens tend to form nematic phase within the polymer network.Fabrication of LCE microstructures is a newly developing area with great growth potential.Taking use of elastomer (PDMS) molds,soft-lithographic methods have been used to fabricate LCE microstructures,which include micropillars and microwires.Soft-lithography has proved to be a feasible way to prepare LCE microstructures as shown by previous studies.LCE capillary fabricated by homemade tubular liquid crystal cell has been developed and employed to mimic the peristaltic crawling locomotion of earthworms.Upon the motion of heat source outside along the capillary axis,a crawling speed of 0.31 mm s-1 is achieved.The kinematics of the biomimetic locomotion has been studied and rationalized with a five-stage model.This crawling locomotion of the LCE capillary can be potentially applied in biomimetic miniature robots and so on.Gold nanorods (AuNRs),which are different from commonly used azobenzene photochromic moieties and carbon nanotubes,have been incorporated into LCE networks to achieve light responsiveness.AuNRs possess advantages in durabiltiy and photothermal conversion efficiency compared with the others.By incorporating AuNRs in side-on LCEs,light-responsive LCE/AuNRs composites have been developed by taking use of the photothermal effect of AuNRs.With inclusion of less than 1 wt％ of AuNRs,a fast (within 3 s) light actuation has been achieved in LCE/AuNR composite actuators upon laser irradiation.By employing LCE gel,the phase transition temperature of LC network is reduced and the light-responsive function at room temperature has been achieved by AuNRs.In this article,some challenges to develop novel micmstructures and realize more efficient stimuli-responses by using side-on LCEs are also discussed from perspectives of the authors.