Designing, Synthesising and Characterizing Supercomplex Nanostructures Based on Liquid Crystalline Frank Kasper Phases by Molecular Rod Self-assembly

Frank Kasper相代表着复杂的最接近的球体四面体堆积，对金属合金的性能起着重要的作用。在这种情况下，金属原子代表通过静电和共价轨道相互作用而相互作用的球体。最近，在胶体颗粒、嵌段共聚聚合物聚集体和树枝状分子的填料中观察到了较大长度的Frank-Kasper相。在这种情况下，球之间界面面积的最小化(如Weaire-Phelan泡沫)导致了这种自组装模式。从我们之前对多亲分子的研究中，我们发现了大量的多亲自组装模式。其中，棒束相由棒状单元连接的球串和立方对称的网络结构组成，其中球体位于网络的分支点。这些新的结构，代表了双连续和胶束立方相的混合体，是通过特殊设计的亲波脂自组装而形成的。在这些复杂的液晶结构中，含有氢键网络的极性球通过棒状的芳香族核心连接在一起。由此产生的网络代表了具有高度复杂超结构的有序液体，其中单个分子仍然可以自由移动。在这方面，它们不同于金属有机骨架(MOF)和共价有机骨架(COF)，它们代表具有固定分子位置的固态结构。本项目的目的是将这一概念扩展到基于新的四面体堆积的更复杂的液晶结构，导致Frank-Kasper相。这将通过将刚性棒状单元、极性末端单元和柔性侧链相结合的波拉型两亲分子的分子设计来实现。自组装模式将根据侧链的体积、长度和分支程度的设计进行定制。最终的科学目标是提供对分子工程的理解，以便在有序液体中形成可预测的高度复杂的纳米结构。该项目将由专注于分子设计、合成和初步表征的Carsten Tschierske教授(MLU Halle)和西安大学的F.Liu教授合作开发。重点对新相结构进行了深入的研究和结构解析。

Frank Kasper phases represent complex closest tetrahedral packings of spheres and play a significant role for the properties of metal alloys. In this case the metal atoms represent the spheres which are interacting by electrostatic and covalent orbital interactions. More recently Frank-Kasper phases on a larger length scale have been observed in packings of colloid particles, aggregates of block-copolymers and dendritic molecules. In this case the minimization of the area of the interfaces between the spheres (e.g. Weaire-Phelan foam) lead to this mode of self-assembly.From our previous studies on polyphilic molecules, we have found a large number of modes of polyphilic self-assembly. Among them the rod-bundle phases formed by strings of spheres connected by rod-like units and network structures with cubic symmetry where spheres are position at the branching points of the networks. These new structures, representing hybrids of bicontinuous and miceller cubic phases were formed by self-assembly of specifically designed bolapolyphiles. In these complex liquid crystalline structures polar spheres involving hydrogen bonding networks are connected by rod-like aromatic cores. The resulting networks represent ordered liquids with highly complex superstructures, where the individual molecules are still free to move. In this respect they are distinct from the metal organic frameworks (MOFs) and the covalent organic frameworks (COFs), representing solid-state structures with fixed positions of the molecules.The aim of this project is to extend this concept to more complex liquid crystal structures based on new tetrahedral packings, leading to Frank-Kasper phases. This will be achieved by molecular design of bola-type amphiphiles combining rigid rod-like units, polar terminal units and flexible lateral chains. The mode of self-assembly will be tailored by the design of the lateral chains with respect to their volume, length and degree of branching. The ultimate scientific goal is to provide an understanding of molecular engineering towards predictable highly complex nano-scale structure formation in ordered liquids. The project will be developed in collaboration between Prof. Dr. Carsten Tschierske (MLU Halle), focussing on molecular design, synthesis and preliminary characterization, and Prof. Dr. F. Liu (Xian Univ.) focussing on the in depth investigation and structural elucidation of the new phase structures.