Phase Transition Studies and Thermodynamic Parameters of Four Members of nO.m Series—A Dilatometric Study

Abstract

Density measurements are carried out on four alkoxy benzylidene alkyl anilines, viz., N-(p-n-methoxy/ethoxybenzylidene)-p-n-dodecyl and tetradecylanilines, 1O.12, 1O.14, 2O.12, and 2O.14. The first three compounds exhibit monovariant nematic phase while the last compound exhibits nematic and smectic-A phase with variable thermal ranges. The density measurements infer the first order nature for Isotropic to nematic (Iso-N) phase transformation while the nematic to smetic-A (N-SmA) transition as weak first order. Thermal expansion coefficient α estimated from density ρ is utilized for the computation of thermodynamic parameters of above liquid crystalline compounds. The temperature variation of different thermodynamic parameters like Moelwyn-Hughes parameter, reduced volume, reduced compressibility, isothermal, isochoric, and isobaric Gruneisan parameters, etc., are estimated. The results are compared with the available data in literature of other compounds.

Keywords:

• Density
• nO.m compounds
• phase transitions
• thermodynamic parameters

Acknowledgments

The authors M. Ramakrishna Nanchara Rao and P. V. Datta Prasad express their deep appreciation to the management of the The Hindu College, Machilipatnam, India, for providing assistance. D. Madhavi Latha and V. G. K. M. Pisipati express their thanks to The Head, ECE Dept. and the management of K. L. University, Vaddeswaram 522 502, India, for providing facilities. This work is supported by the Department of Science and Technology (Grant No: SR/S2/CMP-0071/2008). D. Madhavi Latha acknowledges the financial support of the Department of Science and Technology, Government of India, through the grant No. SR/WOS-A/PS-05/2010.