Phase Diagram and Dielectric Studies in Hydrogen-Bonded Liquid Crystal System

• Published in: Molecular Crystals and Liquid Crystals Vol. 626; no. 1; pp. 12 - 20
• Main Authors: Efremova, E. I., Kydryashova, Z. A., Nosikova, L. A., Kovshik, A. P., Dobrun, L. A., Melnikov, A. B.
• Format: Journal Article
• Language: English
• Published: Philadelphia Taylor & Francis 11-02-2016; Taylor & Francis Ltd
• Subjects: Crystallography; Dielectric constant; Dielectric measurement; Dielectrics; Differential scanning calorimetry; Hydrogen bonding; Hydrogen bonds; intermolecular hydrogen bonding; Liquid crystals; Mathematical analysis; p-n-alkoxybenzoic acids; Permittivity; phase diagram; Phase diagrams; Phase transitions; Thermodynamics
• ISSN: 1542-1406; 1563-5287; 1527-1943
• DOI: 10.1080/15421406.2015.1106220

The thermal and dielectric behaviors of mixtures were investigated for systems of p-n-hexyloxybenzoic acid (6OBA) and p-n-octyloxybenzoic acid (8OBA) by differential scanning calorimetry, polarized optical microscopy, and dielectric measurements. The T-X phase diagram was obtained for this system. Eutectic composition was calculated and received experimentally. Enthalpies of mixing were calculated to describe phase transitions physically. All mixtures show enantiotropic smectic and nematic phases. Dielectric permittivity has higher value for the mixture with fractional proportion of 30 to 70% mol for 8OBA than that for initial acid. It is assumed that co-crystallization of initial compound occurs when the ratio of components is close to equimolar ratio.