Abstract
Three binary systems were prepared by mixing of two different mesogenic derivatives, homologues, the first is azo/ester, namely 4-alkoxyphenylazo-4′-phenyl-4″-alkoxybenzoates (IIn+m) and the second is Schiff base/ester, namely 4-(arylideneamino)phenyl-4″-alkoxy benzoates (In+m). The two corresponding analogues from both series in the binary mixtures investigated are of the same terminal alkoxy chain length. Mesomorphic properties were investigated by differential scanning calorimetry (DSC) and phases identified by polarized optical microscope (POM). Photophysical studies were investigated by UV spectroscopy connected to a hot stage. Results were discussed based on constructed binary phase diagrams. All mixtures were found to exhibit eutectic compositions, with linear or slightly linear nematic and smectic A stability/composition dependences. Geometrical parameters were predicted applying density functional theory (DFT) calculations. Twist angle (θ), aspect ratio, dipole moment and the polarizability of the individual compounds were discussed and correlated with the experimental results to illustrate the enhanced the mesophase stability and the mesophase range of the mixture at the eutectic composition compared with those of their individual components.
Highlights
Nowadays, mixtures of liquid crystalline (LC) materials are of an extensive area of interest [1–8].For practical applications, LC materials exhibiting transition at room temperature and retain their mesomorphic character over a wide range of temperatures are preferred
Binary or ternary mixtures may be symmetric, with the same mesogenic moieties but of different terminal groups, or nonsymmetrical, with different mesogenic units. In both types of binary mixtures, the intermolecular interactions between the two mesogenic cores lead to a significant variation in the optical activity [21–24]
Our present work aims to investigate the mesomorphic and optical activity of binary mixtures made from fromtwo twosystems systems with different mesogens, the Schiff base/ester the azo/ester with different mesogens, the Schiff base/ester (In+m)(In+m) and theand azo/ester (IIn+m)
Summary
Mixtures of liquid crystalline (LC) materials are of an extensive area of interest [1–8]. 22 of of 12 in the mesophase formation, type, thermal stability, and temperature ranges of the LCs compounds [26–32]. Azobenzene an alkyl/alkoxy or a small compact polar substituent [34–37] The role of these groups is to act as moiety is considered to be a good in fragment develop and Azobenzene design a new molecular shape of dipolar parts to introduce anisotropy physicaltocharacteristics. MesogenicLiquid core crystals are attractive for an studying their often with very interesting containing azo group in electro-optical [39]. Esterfor linkages are their commonly used,properties as they offer good advantages the mesogenicproperties core are attractive studying electro-optical [39] Ester linkages such as commonly thermal and wide of stability. The in development and Schiff base linkages haveinteresting been synthesized investigated many interesting investigation of new advanced functional thermotropic liquid crystals functional require thethermotropic proper selection of studies [42–47].
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