Phase Transition Studies in N(p-n-Heptyloxy Benzylidene)p-Toluidine, 70.1, Across I-N,N-SA and SA-SB Phases

The results of density and ultrasonic velocity variation with temperature in N(p-n-heptyloxy benzylidene)p-toluidine, HYBT, 70.1 exhibiting nematic, smectic-A and crystalline smectic-B phases, are presented. The isotropic-nematic, nematic-smectic-A phase transitions are found to be first order while the smectic-A crystal smectic-B transition is weak first order. The thermal expansion coefficient α computed from the molar volume data is presented. The molar sound velocity and molar compressibility of HYBT computed from the density and ultrasonic velocity data in isotropic phase are compared with the values of the other compounds in a homologous series. They are found to be in good agreement with theory.