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

• Applicant: Professor Dr. Carsten Tschierske
• Subject Area: Solid State and Surface Chemistry, Material Synthesis ; Synthesis and Properties of Functional Materials
• Term: from 2018 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 392435074

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.

• DFG Programme: Research Grants
• International Connection: China
• Partner Organisation: National Natural Science Foundation of China
• Cooperation Partner: Professor Feng Liu, Ph.D.