Lyotropic Liquid Crystal Gels: Structure, Rheology, and Stimuli-Response

我们在项目的第一部分中成功地以可控和可复制的方式生产出具有片层、向列和六方有序的溶致液晶（LLC）凝胶后，后续项目将主要关注LLC凝胶作为水基刺激响应材料的具体性能和可能的应用。LLC凝胶是热致液晶凝胶和弹性体（LCEs）的溶致对应物，它们是当今快速发展的软机器人和仿生驱动领域的主力。与热致性凝胶相比，LLC凝胶制备成本低，与水介质兼容，因此它们有望对完全不同范围的化学和生物刺激做出反应。我们认为这是一个非常有希望的前景，非常值得作为我们后续项目的重点。因此，后续项目的最终目标是探索LLC凝胶作为刺激响应材料的潜力。然而，要成功实现这一总体目标，必须首先满足两个基本要求，即：(1)具有量身定制的热、结构和流变性能的（主要是）向列型LLC凝胶的可用性；(2)具有明确定义的宏观各向异性定向配置的排列LLC凝胶的成功制备。因此，在后续项目中将解决的中心研究问题如下：(a)如何合理设计具有定制热、结构和流变特性的（向列）LLC凝胶？LLC亲本体系的组成（表面活性剂、助表面活性剂、水）和凝胶浓度如何影响LLC凝胶的清除温度、溶胶-凝胶温度、取向顺序参数和流变性能？(b)（向列）LLC凝胶如何被加工成具有明确的宏观各向异性定向配置的排列样品？可能的选择有磁场对准、受限几何形状的表面对准或剪切对准。(c)排列的LLC凝胶在水、水溶液或其他与水混溶的溶剂（如醇）中如何膨胀？溶剂吸收如何影响相行为？相关的形状各向异性变化到什么程度？(d)排列的LLC凝胶如何响应温度变化，特别是温度引起的相变？相关的形状变化在多大程度上是各向异性和可逆的？热-机械反应有多快？结合之前项目的结果，这些问题的答案将导致对LLC凝胶的准备、结构和应用的第一个连贯的画面，从而使整个项目有意义地完成。

After we succeeded in the first part of the project to produce lyotropic liquid crystal (LLC) gels with lamellar as well as nematic and hexagonal order in a controlled and reproducible way, the follow-up project will mainly focus on the specific properties and possible applications of LLC gels as water-based stimuli-responsive materials. LLC gels are the lyotropic counterparts of thermotropic liquid crystal gels and elastomers (LCEs) which are today the workhorses in the rapidly emerging fields of soft robotics and biomimetic actuation. In comparison to their thermotropic counterparts, LLC gels are cheap to prepare and compatible to aqueous media - they are thus expected to respond to a completely different range of chemical and biological stimuli. We consider this an extremely promising perspective that is well worth being placed in the focus of our follow-up project. The ultimate goal of the follow-up project is thus to explore the potential of LLC gels as stimuli-responsive materials. However, to successfully pursue this overall objective, two basic requirements must first be met, namely:(1) the availability of (mainly) nematic LLC gels with tailored thermal, structural and rheo-logical properties and(2) the successful preparation of aligned LLC gels with well-defined macroscopically anisotropic director configurations.The central research questions which will thus be addressed in the follow-up project are as follows:(a) How can (nematic) LLC gels with tailored thermal, structural and rheological properties be rationally designed? How does the composition of the LLC parent system (surfactant, cosurfactant, water) and the gelator concentration affect the clearing temperature, the sol-gel temperature, the orientational order parameter and the rheological properties of the LLC gels?(b) How can (nematic) LLC gels be processed into aligned specimens with a well-defined macroscopically anisotropic director configuration? Possible options are magnetic field alignment, surface alignment in restricted geometries, or shear alignment.(c) How do aligned LLC gels swell in water, aqueous solutions or other water-miscible solvents such as alcohols? How does the solvent absorption affect the phase behaviour? To which extent is the associated change in shape anisotropic?(d) How do aligned LLC gels respond to changes in temperature and, in particular, to temperature induced phase transitions? To which extent is the associated change in shape anisotropic and reversible? How fast is the thermo-mechanical response?Together with the results from the preceeding projects, the answers to these questions will lead to a first coherent picture of the preparation, the structure and the application of LLC gels, which allows a meaningful completion of the overall project.