Free Space in Liquid Crystals – Molecular Design, Generation and Usage

Abstract
In the last 50 years an important aim for the molecular and materials design was the generation of space for the uptake of guest molecules in macrocycles, cryptands, in dendrimers as monomolecular containers, and recently in porous networks like MOFs and COFs. Such molecular, oligomeric and polymer materials can be applied for sensing, separation, catalysis, drug delivery and gas storage among others. Typically, completely empty space is unfavorable, especially for fluid materials with a high molecular mobility like the liquid crystals (LC). This talk summarizes the research on the formal generation of void in LCs and it will highlight that the rational design of molecules can lead to unconventional mesophases by filling efficiently the provided space.

The topic was recently further developed by the investigation on shape-persistent star mesogens. Here the incorporation of guests by physical mixing, supramolecular and covalent bonds results in highly ordered columnar and lamellar LC structures. Recently, discotic mesogens have been combined with semiconducting arms to generate space providing star mesogens. The mixing with the same mesogen in which the free space was sterically overcrowded by fullerenes covalently attached via spacers caused the discovery of a new supramolecular Click process providing a material with triple nanosegregated donor-acceptor and antenna building blocks, which will be of interest for the area of future organic photovoltaics.

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[2] M. Lehmann, M. Dechant, M. Holzapfel, A. Schmiedel, C. Lambert, Angew. Chem. Int. Ed. 2019, 58, 3610-3615.