Phase Transition and Thermodynamic Parameters of Liquid Crystalline Mixtures – A Dilatometric Study

Shahina ¹ , C. M. Subhan² , K. Fakruddin³

Section:Research Paper, Product Type: Isroset-Journal
Vol.6 , Issue.6 , pp.48-56, Dec-2018

CrossRef-DOI:   https://doi.org/10.26438/ijsrpas/v6i6.4856

Online published on Dec 31, 2018

Copyright © Shahina, C. M. Subhan , K. Fakruddin . This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
 

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Abstract :
In the present work heptyl amino methyl-hydxoy phenoxy biphenyl carbonitrile Liquid crystals of spacer length n=6, 7 and hexyloxy benzylidene amino phenyl benzoates of terminal group m=10, 13 are choosen. Each of the above two series of compounds are taken in equal concentration and their mixtures C1 and C2 are prepared. The transition temperatures and optical textures of these mixtures are recorded by using polarizing optical microscope. The temperature variation of density is measured by dilatometer. The density and thermal expansion coefficient results reveals that the mixture C1 exhibits nematic, smectic A and smectic B phases, the mixture C2 exhibits only nematic and smectic A phases. The temperature dependence of number of thermodynamic parameters viz., Moelwyn-Hughes parameter, Beyer’s nonlinearity parameter , the reduced molar volume, Sharma parameter, fractional free volume, isothermal, isobaric, isochoric Gruneisen parameters etc., are estimated. The results reveal that all the thermo dynamical parameters show characteristic changes in the vicinity of phase transformation. The results are discussed based on the data obtained

Key-Words / Index Term :
Liquid crystalline mixtures, optical textures, phase transitions, density, thermal expansion coefficient and thermodynamic parameters

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