DENSITY STUDIES IN TEREPHTHALYLIDENE-BIS-P-N-ALKYLANILINES

The temperature dependence of density in terephthalylidene-bis-p-n-alk ylanilines (TBAA5 and 6) is studied to investigate the phase transitio ns, associated volume jumps, order of the transitions, estimated press ure dependence of transition temperatures, and pretransitional effects . The compounds exhibit nematic, smectic A, smectic C, smectic F, smec tic G and smectic H phases with higher clearing temperatures. The smec tic A to smectic C transition, which is a fluctuation induced first or der transition in TBAA9, is found to be a second order transition in T BAA5 and 6. The results are discussed in the light of other experiment al reports. The estimated pressure dependence of transition temperatur es along with the reported experimental P-T data are discussed. The N- S(A) transition is first order in TBAA5 and 6. The studies across othe r transitions are also discussed.