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Abstract
Temperature gradient of refractive indices, dn e /dT and dn o /dT, of the isotropic mixtures of the liquid crystals of nO.m compounds, namely N-(p-n-butyloxybenzylidene)-p-n-hexyl aniline, 4O.6, and N-(p-n-hexyloxybenzylidene)-p-n-butyl aniline, 6O.4, are estimated using the refractive index data. The former one exhibits a second-order nematic-to-smectic-A (N-SmA) phase transition, while the later compound shows a first-order (N-SmA) phase transition. These two compounds exhibit high clearing temperatures, i.e. well above the room temperature. It is found that the two materials and the mixtures exhibiting second-order N-SmA transition show the crossover temperatures (T CO’s) well below the room temperature while the mixtures showing first-order transition exhibiting T CO’s well above the room temperature.
Acknowledgements
The author D. Madhavi Latha expresses her thanks to The Head, ECE Department and the management of K. L. University, Vaddeswaram 522 502, India for providing facilities. The authors Dr V.G.K.M. Pisipati and P.V. Datta Prasad thank the Management, S.S.D. Polymers, Machilipatnam, India. This work was supported by the Department of Science and Technology (Grant No: SR/S2/CMP-0071/2008) and D. Madhavi Latha acknowledges the financial support from DST-WOS-A (Grant No: SR/WOS-A/PS-05/2010).