| Autor: |
Rao, D. Venkata, Pardhasaradhi, P., Pisipati, V. G. K. M., Prasad, P. V. Datta |
| Předmět: |
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| Zdroj: |
Molecular Crystals & Liquid Crystals; 2015, Vol. 623 Issue 1, p87-103, 17p |
| Abstrakt: |
As a part of our systematic studies on liquid crystals of nO.m, n.Om, nO.Om and n.m homologous series, n-(p-n-alkoxy/alkylbenzylidene)-p-n-alkyl/alkoxy anilines, we present in this article the nature of phase transitions across isotropic–nematic exhibited by all the compounds mentioned below. Further, the orientational order parameter in the nematic phase of N-(p-n-propyl/propyloxy benzylidene)-p-n-alkoxy anilines, 3.Om and 3O.Om with m = 6–8 are estimated from the molecular polarizabilities calculated using the experimental refractive indices and density results. The molecular polarizabilities αeand αoare obtained for all the compounds using the above results for both Vuks and Neugebauer local field models applicable to nematic liquid crystal. αeand αocalculated in this way are used to obtain Δα. The polarizability anisotropy in the perfect order (absolute K) is calculated theoretically using the δ-function model developed by Lippincott et al. and molecular vibration method. These enabled the calculation of the orientational order parameter S. The values of polarizability anisotropy for both local electric field models differ significantly. No criterion is known to decide which value is correct. To avoid the determination of uncertain α and Δα values considering different local field models, a simple procedure developed by Kuczynski et al. was used for evaluation of S, based solely on birefringence measurement and this value of S is compared with those obtained from field models. [ABSTRACT FROM PUBLISHER] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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