Mesogenic Behavior of New Derivatives Containing Azo-Ester-Imine Links with Different Substituted Alkoxy Groups as Terminal Tails

摘要

Two series of ten ester derivatives with four aromatic rings linked together by three different linkages (azo/ester/imine), 4-((4-substituted)diazenyl)phenyl 4-((4-alkoxybenzylidene)amino)benzoate (IVn X=OCH3 and V-n X=Br) were synthesized. These derivatives have an alkoxy chain in the para position of the phenyl ring with different lengths (n=3, 4, 6, 7, and 12) on one terminal side while the other side was substituted by methoxy and bromo groups linked to the p-position of phenyl. The structures of all synthesized derivatives were proven by nuclear magnetic resonance (H-1-NMR, C-13-NMR), elemental analysis (C,H,N), and Fourier-transform infrared spectroscopy (FT-IR). The Mesophase textures of the final esters were observed by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). Only the nematic texture was observed in the methoxy derivatives while nematic and smectic A textures were shown in the bromo mesogens. All the homologous showed mesogenic behavior with wide thermal stability. From the results, it was found that the liquid crystalline behaviors of these derivatives are dependent on the substituted group (-X) and the length of the alkoxy chain. The mesogenic behavior of these compounds was compared with other mesogens that have similar structures.