Novel cholesterol-based liquid crystalline dimers: the α-cyanostilbene group served as a photofluorophore and mesogenic moiety

Abstract

ABSTRACT Cyanostilbene units are vigorous candidates for chromophores and mesogens. Therefore, a series of dimer liquid crystals based on cyanostilbene and cholesterol were synthesised and characterised. The structure conforms to the molecular design and its physicochemical properties are stable. With the growth of the inner spacer flexible carbon chain, the mesomorphic properties are greatly different: not only the odd–even effect of the clearing points (/clearing enthalpies) is caused but also the samples exhibit increasingly complex enantiotropic mesophases, including SmC*, SmA and N* phases. Corresponding textures of these phases were observed, such as polygonal textures, focal-conic textures with dechiralisation lines and oily streaks textures, etc., and phase structures were further verified using variable-temperature XRD. Through the combined use of UV and fluorescence emission spectrometers, it was found that the increase of water content caused the enhancement of fluorescence intensities and the redshift of UV absorptions, which confirmed the fascinating aggregation-induced emission enhancement (AIEE) effect of the ChM-CN molecules.