Mesomorphism in a binary mixture of non-mesogens: A thermo-physical study

A comprehensive study on a liquid crystal formed by mixing two non-mesogens, viz., cholesterol and cetyl alcohol has been carried out. Polarized microscopic observations confirmed that the mixture exhibits smectic A phase below 48.2 °C. The mechanism possible for the formation of ordered liquid crys...

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Bibliographic Details
Published in:Physica. B, Condensed matter Condensed matter, 2010-11, Vol.405 (21), p.4586-4593
Main Authors: George, A.K., Singh, R.N., Arafin, S., Carboni, C., Al Harthi, S.H.
Format: Article
Language:English
Subjects:
Acoustic impedance
Adiabatic compressibility
Compressibility
Condensed matter
Condensed matter: structure, mechanical and thermal properties
Density
Equations of state, phase equilibria, and phase transitions
Exact sciences and technology
Grüneisen parameter
Liquid crystals
Mesomorphism
Phase transformations
Physics
Specific heat
Specific heat ratio
Specific phase transitions
Thermodynamics
Transitions in liquid crystals
Ultrasound
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Summary:A comprehensive study on a liquid crystal formed by mixing two non-mesogens, viz., cholesterol and cetyl alcohol has been carried out. Polarized microscopic observations confirmed that the mixture exhibits smectic A phase below 48.2 °C. The mechanism possible for the formation of ordered liquid crystal phase when two non-mesogens are mixed is discussed. Density measured using a precision density meter was found to drop drastically in the vicinity of isotropic to smectic A transition temperature. The density fluctuations at the transition are discussed on the basis of: (i) the long wavelength limit of the structure factor and (ii) the critical exponent evaluated using modified Landau—de Gennes theory. The ultrasound velocity, determined using the interferometer method, drops drastically near the smectic A—isotropic transition temperature. The temperature-dependent data of density and ultrasound velocity enabled the evaluation of the adiabatic compressibility and acoustic impedance. The specific heat at constant pressure measured using differential scanning calorimetry shows a large increase in the vicinity of the phase transition. A correlation of thermodynamic functions to thermo-elastic properties was established through thermodynamic route. This relationship, along with experimentally measured quantities forms the basis for the thermo-physical characterization of the mixture. This facilitated the evaluation of specific heat at constant volume, the ratio of specific heats, the isothermal compressibility and the Grüneisen parameter across the smectic A—isotropic phase transition.
ISSN:0921-4526
1873-2135
DOI:10.1016/j.physb.2010.08.045