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Study of Refractive Indices, Density and Order Parameters of Two Nematogens and Their Eutectic Mixture

100%

Datta Sarkar S., Choudhury B.

issue 4

665-669

The compounds 5-pentyl-2-(4'-cyanophenyl) pyrimidine [CM 7035] and 4-n-butyl-4'-ethoxytolan [PTP4O2] and mixtures of different mole fractions of them show nematic phase with supercooling effect. From the phase diagram the equimolar mixture is found to be the eutectic mixture. Temperature variation of the density and refractive indices (n_{o}, n_{e}) of the pure compounds and their eutectic mixture have been reported here. The density and birefringence values of the eutectic mixture are found to be less than that of pure compounds. However the average refractive index values of eutectic mixture almost coincide with those of CM 7035 which are much less than those of PTP4O2. The refractive indices and density values have been analyzed to obtain the orientational order parameters. Experimental order parameter values of the pure compounds and the eutectic mixture are compared with theoretical Maier-Saupe values. The possible reasons for disagreement between theoretical and experimental values for the pure compounds are discussed. The agreement between theoretical and experimental order parameters are fairly good for the eutectic mixture.

Effect of Temperature on the Refractive Indices of Liquid Crystals and Validation of a Modified Four-Parameter Model

81%

Thingujam K., Sarkar S., Choudhury B., Bhattacharjee A.

Acta Physica Polonica A

2012

vol. 122

issue 4

754-757

The variation of refractive indices with temperature of three pure nematogenic compounds 5OCB, CPHB and 6CHBT were studied experimentally using thin prism technique. The refractive indices n_{o} and n_{e} were measured using 633 nm lines from a He-Ne laser. A modified four-parameter model was taken which is based on the Vuks equation describing the effect of temperature on the refractive indices of liquid crystals. In this paper we report the variation of refractive indices of these three liquid crystals with temperature, using the thin prism method. The variation in birefringence was determined experimentally. The variation in refractive indices and birefringence were also fitted theoretically using the modified Vuks equation. On comparison, the theoretically fitted values show close agreement with the experimental values.

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2 Acta Physica Polonica A

1 2012

1 2010

2 Choudhury B.

1 Bhattacharjee A.

1 Datta Sarkar S.

1 Sarkar S.

1 Thingujam K.

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Study of Refractive Indices, Density and Order Parameters of Two Nematogens and Their Eutectic Mixture

Effect of Temperature on the Refractive Indices of Liquid Crystals and Validation of a Modified Four-Parameter Model