Phase transitions across different liquid crystalline modifications in compounds with octa decylaniline as one end group: a dilatometric study

Abstract

The phase-transition studies such as the variation of density with temperature is carried in four newly synthesized compounds namely N-(p-n-decyloxybenzylidene)-p-n-octadecylaniline, 10O.18, N-(p-n-octadecyloxybenzylidene)-p-n-octadecyl aniline, 18O.18, (p-n-phenylbenzylidene)-p-n-octadecyl aniline, PB18A and terephthalyidene-bis-p-n-octadecylaniline, TB18A. These compounds exhibit a variety of phase variants such as isotropic-to-smectic-F (Iso–SmF) in 10O.18 and 18O.18, isotropic-to-smectic-A to-smectic-B (SmA–SmB) in PB18A and Isotropic-to-smectic-C to-smectic-I to-smectic-F (SmC–SmI–SmF) in TB18A. The density and thermal expansion coefficient results reveal that all the phase transitions studied in this article show first/second-order nature. The estimated values like density jumps and the thermal expansion coefficient maxima from the density data at the transitions exhibit characteristic changes. The results are discussed in light of the body of the data available.

Keywords:

• phase transitions
• density
• thermal expansion coefficient

Acknowledgements

The authors, D. Madhavi Latha and Dr V.G.K.M. Pisipati, express their thanks to The Head, ECE Department and the management of K.L. University, Vaddeswaram 522 502, India for providing facilities. This study is supported by the Department of Science and Technology (Grant no: SP/S2/CMP-0071/2008). M.V.V. Nagi Reddy, P. Pardhasaradhi and Dr P.V. Datta Prasad express their deep appreciation to the management of The Hindu College, Machilipatnam, India for providing assistance.