B08 • Highly Organized Ion- Conducting Materials Based on Borate Anions

Ion conducting materials are essential in many modern devices such as batteries, supercapacitors, fuel cells, dye-sensitized photovoltaic cells, or electrochromic devices. This project aims for the design, synthesis, and application of novel ion conducting materials based on weakly coordinating perfluoroalkyl- and cyanoborate anions. The key objective is the development of perfluoroalkylboratecontaining ion conductors based on liquid crystals (LCs) that are superior in properties to state-of-theart non-borate-containing systems.
To fulfill our objective, we will focus on two classes of materials: Class 1 will consist of multiple mesophases with varying degrees of organization: (I) lamellar, (II) bicontinuous cubic, (III) columnar LCs, and soft crystalline phases. The materials will contain LC-inducing building blocks that are covalently connected to functionalized perfluoroalkylborate anions via flexible spacers. These compounds will be explored as function of spacer length, nature, number and length of peripheral flexible chains to form ionic liquid-crystalline (ILC) 1D (lamellae), 2D (columnar), or 3D (bicontinuous cubic) ordered materials. These anisotropic liquids provide pathways for cation conduction with varying size and order. A second class of materials (Class 2) will be based on promising LC compounds, which will be either transformed to a LC gel with known organic gelators, equipped with functional groups allowing solidification by polymerization, or will be incorporated into crystalline organic cages (COFs) in collaboration with the group of Florian Beuerle (University of Tübingen) in order to increase the level of organization and to study the influence of confinement on the structure and properties. The differently ordered materials from Class 1 and Class 2 will be studied in detail by different methods such as polarized optical microscopy (POM) and X-ray scattering (XRS) to uncover the mesoscale structure. Tailored NMR spectroscopic methods will reveal structural details on a nanoscale complementary to insights from the other analytical tools and together with theoretical methods help to validate X-ray based structural models and understand structure-property relationships. For this purpose, the soft crystals formed at lower temperature give access to information on close contacts, which will be correlated with the corresponding liquid-crystalline structures. The most competitive materials will be tested in lab-scale electrochemical devices.
Structure-property relations will be returned into a feedback loop for continuous improvement of molecular design and properties.