Controlling liquid and liquid crystalline network formation by core-fluorination of hydrogen bonded supramolecular polycatenars

• Published in: Journal of molecular liquids 2021-06, Vol.332, p.115870, Article 115870
• Main Authors: Alaasar, Mohamed, Schmidt, Jaques-Christopher, Cai, Xiaoqian, Liu, Feng, Tschierske, Carsten
• Format: Article
• Language: English
• Subjects: Azobenzenes; Cubic phases; Helical self-assembly; Hydrogen bonding; Mirror symmetry breaking; Photo switching; Polycatenar liquid crystals
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2021.115870

Photo-switchable materials with liquid crystalline (LC) properties and being capable of showing mirror-symmetry breaking are of special interest from a fundamental scientific point of view as well as for the development of π-conjugated materials with tailored superstructures for optical, emissive and photonic materials. Herein we report two new series of supramolecular photosensitive polycatenar (multi-chained) mesogens formed by hydrogen bonding interaction between a taper shaped triple-chain benzoic acid as the hydrogen bond-donor and fluorinated azopyridines with only a single chain as hydrogen bond-acceptors. The self-assembly of these materials was characterized by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and X-ray diffraction (XRD). Depending on the position of the fluorine atom different types of LC phases were observed, including spontaneously chiral isotropic liquid (Iso1[*]) and bicontinous cubic phases (Cubbi[⁎]/I23), as well as achiral cubic (Cubbi/Ia3̄d) and non-cubic 3D phases with tetragonal symmetry. This report provides guidelines for the application of core fluorination at different positions as a powerful tool for controlling spontaneous helical self-assembly in supramolecular liquid and liquid crystalline materials. [Display omitted] •Novel photo-sensitive fluorinated hydrogen-bonded liquid crystals are reported.•The formation of the hydrogen-bond was proved via FTIR.•The liquid crystalline behaviour was characterized by DSC, PLM and XRD.•Helical self-assembly is observed in liquid and liquid crystalline networks.•First examples of supramolecular complexes with 3D tetragonal phases are reported.