Phase Transition, Birefringence and Orientational Order Parameter Studies in Four Members of Benzylidene Aniline Liquid Crystals

Abstract:

The nature of the phase transitions across isotropic–nematic (IN) and nematic–smectic-A (N-SmA) are carried out using density measurements in N-(p-n-ethoxy benzylidene)-p-n-pentyl aniline, 2O.5, N-(p-n-methoxy benzylidene)-p-n-pentyloxy aniline, 1O.O5, N-(p-n-ethyl benzylidene)-p-n-dodecyl aniline, 2.12 and N-(p-n-butyl benzylidene)-p-n-dodecyl aniline, 4.12. The compounds exhibit IN, IN, IN and INSmA phase sequences respectively with varying thermal ranges suitable for the study of birefringence. The birefringence studies are carried out using Newton’s rings and wedge techniques which provide δn = (n_e - n_o) (the birefringence) n_e, and n_o respectively. The orientational order parameter, S is evaluated (i) directly from δn and Δn (the birefringence in perfect order), independent of the local field that the nematic molecule experiences and (ii) from molecular polarizabilities estimated from n_e, n_o and density values assuming isotropic as well as anisotropic field that the nematic molecule experiences. The estimated order parameter from the different techniques is compared with one another and with the literature data.

• Periodical: Solid State Phenomena (Volumes 181-182)
• Pages: 115-119
• DOI: https://doi.org/10.4028/www.scientific.net/SSP.181-182.115
• Online since: November 2011
• Authors: P.V. Datta Prasad, G. Padmaja Rani, V.G.K.M. Pisipati
• Keywords: Birefringence, Molecular Polarizability, Order Parameter, Phase Transition

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