Synthesis and Characterization of New Thermotropic Liquid Crystalline Compounds with Bromo-Substituted Terminal Group and Azo Vinyl Ester Linkages

ABSTRACT

A novel series of liquid crystal (LC) materials based on azo-vinyl ester, specifically RO-C₆H₃(-OCH₃)–CH=CH–COO–C₆H₃(-CH₃-)–N=N–C₆H₄ –Br, has been synthesized and investigated to understand the influence of molecular structure on liquid crystal properties. This series aims to provide novel thermotropic LC materials to the scientific and technological research community. The series includes 12 members (C₁ toC₈, C₁₀ , C₁₂ , C₁₄ & C₁₆ ), out of these some compounds exhibit enantiotropic smectic & nematic phase and some compounds monotropic liquid crystal behavior. Transition temperatures and textures of the homologues were determined using a polarizing optical microscope (POM) equipped with a heating stage. The phase transition curves (Cr-I/M, Sm-N/I, N-I or I-N) in the phase diagram followed expected patterns. Analytical and spectral data confirmed the molecular structures of the homologues. Thermal stabilities of the smectic and nematic phases were 101.2°C and 115.2°C, respectively, with the total mesophase lengths ranging from 4.4 °C to 39.5 °C. The liquid crystal properties of this novel series were compared with those of structurally similar series.

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