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

摘要

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.