Exploring mesomorphic properties and thermal behavior of novel thermotropic liquid crystals featuring bromo-substituted terminal groups and azo-embedded chalconyl ester linkages through synthesis and characterization

In this research, a novel set of azoester derivatives featuring a bromo terminal group was synthesized and meticulously characterized to assess their mesomorphic characteristics. These compounds were synthesized via esterification reaction involving 4-n-alkoxy-3-methoxy cinnamic acid and 4-((4-bromophenyl) diazenyl)-2-methylphenol. Analysis revealed 12 distinct derivatives displaying predominantly nematogenic behavior, with mesophase initiation observed from the earliest homologue. The mesophase span varied from 4.8°C to 30.9 °C. The decline in the isotropic temperature of the liquid crystal (LC) compounds with increasing carbon chain length underscored the impact of chain flexibility. Various characterization techniques including Fourier-transform infrared spectroscopy (FT-IR), mass spectroscopy, proton nuclear magnetic resonance (1H-NMR), Gauss view, and elemental analysis were employed to probe the compounds' attributes. Polarized optical microscopy (POM) confirmed the presence of mesogenic phases, while differential scanning calorimetry (DSC) elucidated the thermal properties of select homologues. Additionally, a comparative analysis of the mesomorphic behaviors of the novel azoester series with structurally akin series was conducted, yielding insights into their distinctive properties and potential applications. This study contributes significantly to the comprehension of the intricate relationship between molecular structure and mesophase behavior, providing crucial groundwork for the future design and advancement of liquid crystal materials.