Density Studies in Terephthalylidene-BIS-p-n-Decylaniline

Abstract

The temperature dependence of density in terephthalylidene-p-n-decylaniline (TBAA10) is carried out to probe the phase transitions, associated volume jumps, order of the transitions, and to estimate the pressure dependence of transition temperatures and pretransitional effects. The compound exhibits smectic A, smectic C, smectic I, smectic F and smectic G phases. The isotropic-smectic A and smectic C-smectic I phase transitions are found to he first order and the calculated thermal expansion coefficient also supported the density results. The smectic A-smectic C and for the first time smectic I-smectic F transitions are detectable by density changes. The calculated pressure estimate of transition temperatures from the density-enthalpy data and volume changes associated with the phase transitions are compared with the reported P-T data using metabolemeter. The observed two phase coexistence of the smectic A-isotropic and smectic A-smectic C phases in the vicinity of the phase transitions is compatible with reported results. The volume jumps associated with the smectic A—isotropic transition in other compounds are also presented.

Keywords:

• phase transitions
• density
• order of the phase transitions
• TBAA (10)