C. R. C. Prabhu, V. G. K. M. Pisipati: Dilatometric Studies across Intra-Smectic Transitions in Some Homologues of N-(p-n-octyloxybenzylidene)p-n-alkylanilines

Crystal Research and Technology

Cryst. Res. Technol. 37 (2002) 269 - Abstract -

C. R. C. Prabhu, V. G. K. M. Pisipati*

Faculty of Physics, RVR & JC College of Engineering, Affliated to Nagarjuna University, Chandramoulipuram, Chowdavaram, Guntur, India
*Centre for Liquid Crystals Research and Education, Faculty of Physical Sciences, Nagarjuna University, Nagarjuna Nagar, India

Dilatometric Studies across Intra-Smectic Transitions in Some Homologues of N-(p-n-octyloxybenzylidene)p-n-alkylanilines

The variation of density with temperature in four homologues of N-(p-n-octyloxy benzylidene)p-n-alkylanilines, 8O.m’s, viz., N-(p-n-octyloxybenzylidene)p-n-pentylaniline, 8O.5, N-(p-n-octyloxybenzylidene) p-n-hexylaniline, 8O.6, N-(p-n-octyloxybenzylidene)p-n-heptylaniline, 8O.7, and N-(p-n-octyloxybenzylidene)p-n-nonylaniline,8O.9, is reported. Results infer first order nature of isotropic to smectic-A (IA), smectic-A to smectic-B (AB) and smectic-C to smectic-B (CB) transitions, while smectic-A to smectic-C (AC) transition is found to be second order. The pressure dependence of the transition temperatures is estimated from the Clausius-Clapeyron equation using density and enthalpy data. Pre-transitional effects are estimated in the vicinity of fluctuation dominated non-linear regions of isotropic to smectic-A phase transition in all the compounds and the results are discussed in the light of the available data on other nO.m compounds.

Keywords: nO.m, smectics, phase-transitions, dilatometry, pre-transitional effects

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