Phase transition studies in (p-n-phenylbenzylidene)-p-alkoxy anilines

The variation in density with temperature in seven compounds of p-n-(phenyl benzylidene)-p-alkoxy anilines, PBnOA homologous series has been carried out. The compounds with the alkoxy chain number, n = 1, 3–8, exhibit monovariant nematic phase N (n = 1 and 3), bi-variant NB (n = 4–6) and tri-variant NAB (n = 7 and 8) phases. The density and thermal expansion coefficient results reveal that the phase transitions present viz, isotropic to nematic, nematic to SmA, nematic to SmB, nematic to solid crystal and SmA to SmB in these compounds show first-order nature as expected. Further, these results reveal that all the parameters show characteristic change in the vicinity of the phase transformation. The results are discussed in light of the body of the data available.