Refractive Indices and Orientational Order Parameter of Five Liquid Crystals in Nematic Phase

1980 ◽  
Vol 61 (3-4) ◽  
pp. 191-206 ◽  
Author(s):  
A. K. Zeminder ◽  
S. Paul ◽  
R. Paul
Keyword(s):  
Liquid Crystals ◽  
Order Parameter ◽  
Nematic Phase ◽  
Orientational Order ◽  
Refractive Indices ◽  
Orientational Order Parameter

Studies on binary mixtures of 4-pentyloxy-4′-cyanobiphenyl with three 4, 4′-di(alkoxy)azoxybenzenes

2010 ◽  
Vol 18 (2) ◽  
Author(s):  
B. Jaishi ◽  
P. Mandal ◽  
R. Dąbrowski
Keyword(s):  
Binary Mixtures ◽  
Order Parameter ◽  
Nematic Phase ◽  
Transition Point ◽  
Orientational Order ◽  
Smectic Phase ◽  
Refractive Indices ◽  
Orientational Order Parameter ◽  
Polarizability Anisotropy ◽  
Good Agreement

AbstractEighteen binary mixtures of 4-pentyloxy-4′-cyanobiphenyl (5OCB) and 4, 4′-di(alkoxy)azoxybenzenes (nOAB) with n = 5, 6, and 7 at different concentrations have been studied in detail. Over a wide concentration range, induced SmA phase was observed in all the mixtures except in one. In most of the mixtures, the refractive indices no, ne, and Δn lie between the values of pure components. The optical birefringence of the mixtures is found to decrease non-additively with concentration. The molecular polarizability anisotropy and the orientational order parameter <P2> of the mixtures were calculated. Nature of variation of polarizability anisotropy with concentration is similar to that of Δn. In allmixtures <P2> is more in smectic phase than in nematic phase and it also shows non-additive behaviour. Observed <P2> values of the mixtures were compared with McMillan’s and Maier-Saupe theoretical values and good agreement is found in some mixtures. The transition temperatures obtained by fitting <P2> data to McMillan’s theory agree with the observed values within a few degrees. Ratio of elastic constants K33 and K11 is determined for mixtures having nematic phase and found to diverge at TNA transition point.

Optical properties of a liquid crystal with small ordinary and extraordinary refractive indices and small optical anisotropy

2014 ◽  
Vol 22 (3) ◽  
Author(s):  
J. Kędzierski ◽  
K. Garbat ◽  
Z. Raszewski ◽  
M. Kojdecki ◽  
K. Kowiorski ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Liquid Crystal ◽  
Optical Anisotropy ◽  
Order Parameter ◽  
Orientational Order ◽  
Refractive Indices ◽  
Orientational Order Parameter ◽  
Unknown Density ◽  
Abbe Refractometer

AbstractOptical properties of a nematic liquid crystal with small refractive index and small birefringence were studied. The ordinary and extraordinary refractive indices and birefringence were measured as functions of temperature by using an Abbe refractometer and wedge nematic cells. From values of these indices the nematic orientational order parameter was calculated by using several methods and corresponding mathematical models. Kuczyński et al. method was found to be suitable for determining the order parameter also for materials featuring small ordinary refractive index, with unknown density.

Elastic Constants of Nematic Phenylpyrimidines Determined by Two Different Methods

1990 ◽  
Vol 45 (1) ◽  
pp. 37-42 ◽  
Author(s):  
A. Scharkowski ◽  
H. Schmiedel ◽  
R. Stannarius ◽  
E. Weißhuhn
Keyword(s):  
Liquid Crystals ◽  
Temperature Dependence ◽  
Elastic Constants ◽  
Optical Method ◽  
Order Parameter ◽  
Diamagnetic Susceptibility ◽  
Orientational Order ◽  
Orientational Order Parameter ◽  
H Nmr ◽  
Electric And Magnetic Fields

AbstractA survey of various methods to measure the elastic constants Ki of nematic liquid crystals is given. To determine K1, K3 and the anisotropy of the diamagnetic susceptibility Δx of two members of the 5n-hexyl-2-[4n-alkyloxy-phenyl]-pyrimidines and a mixture of both, we used a combined electromagneto- optical method, consisting in independent measurements of the optical phase difference in electric and magnetic fields acting on the same cell. The temperature dependence of the K1- and K3-values for these phenylpyrimidines can be explained by common theories. The Δx data show the same temperature dependence as the values of the orientational order parameter S obtained by 1H-NMR.

scholarly journals An Optical Study to Estimate Orientational Order Parameter on Some Benzylideneaminophenylbenzoate Liquid Crystals

2016 ◽  
Vol 129 (3) ◽  
pp. 284-288 ◽  
Author(s):  
C.M. Subhan ◽  
R. Jeevan Kumar ◽  
P. Panduranga ◽  
B. Jayashreeand ◽  
K. Fakruddin
Keyword(s):  
Liquid Crystals ◽  
Order Parameter ◽  
Orientational Order ◽  
Orientational Order Parameter ◽  
Optical Study
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