Design and mesomorphic behaviour of novel four-ring chalcone-terephthalate-based liquid crystals

Abstract

In this study, novel thermotropic calamitic liquid crystalline molecules comprising four-benzene-ring molecular core having chalcone and ester linking groups with n-dodecyloxy chain at one end and (S)-2-methylbutyloxy chiral group or a linear-chain homologous series with increased carbon atoms (n = 6, 8, 10, and 12) at other terminal have been presented. The chemical structures of the synthesized chalcone derivatives were confirmed by classical spectroscopic methods such as proton nuclear magnetic resonance, 13C-attached proton test nuclear magnetic resonance, and high resolution mass spectroscopy as well as elemental analysis technique. The liquid crystalline features of all compounds have been determined by polarized optical microscopy and differential scanning calorimetry. Also, to provide insight into the decomposition behavior of target compounds, thermogravimetric analysis were performed. According to the polarized optical microscopy and differential scanning calorimetry analyses, all molecules show enantiotropic mesophases. While the mesogens having (S)-2-methylbutyloxy chiral segment and hexyloxy chain display the chiral smectic A and smectic A phases with a broad mesomorphic range, respectively, the members with longer alkyloxy chains provide the smectic C phase in addition to the smectic A phase with a slight decrease of clearing points. This work will contribute to the investigation of the relationship between the molecular structure and mesomorphic properties in terms of the type and the length of the terminal chains in the liquid crystal field.