Study of Variation in Order Parameter with Temperature of Mixtures of Nematic and Cholesteryl Liquid Crystal

2011 ◽  
Vol 181-182 ◽  
pp. 92-95
Author(s):  
Shezan Hasware ◽  
Ratnaraaj Parekh ◽  
Anil Devlekar ◽  
S.M. Bhatia
Keyword(s):  
Phase Transition ◽  
Refractive Index ◽  
Liquid Crystal ◽  
Order Parameter ◽  
Refractive Indices ◽  
Transition Temperatures ◽  
Fabry Perot ◽  
Mixture Samples ◽  
Crystal Mixture ◽  
Abbe Refractometer

The mixtures of nematic [4-Hexyloxy-4-Biphenyl carbonitrile] and cholesteryl propionate were investigated at various temperatures. Measurements of refractive index and transition temperatures were noted by using an Abbe refractometer with a heating arrangement. Ordinary and extraordinary refractive indices were obtained which helped us in calculating the order parameter and its variation with temperature. We also carried out Fabry-Perot Scattering Studies (FPSS) on our samples to confirm the various transition temperatures. Photographs of liquid crystal mixture samples placed between crossed nicols are taken at various temperatures to observe the phase transition.

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.

Refractive index measurements and order parameter determination of the liquid crystal p-ethoxybenzilidene-p-n-butylaniline

1981 ◽  
Vol 59 (4) ◽  
pp. 515-520 ◽  
Author(s):  
P. Palffy-Muhoray ◽  
D. A. Balzarini
Keyword(s):  
Refractive Index ◽  
Liquid Crystal ◽  
Order Parameter ◽  
Orientational Order ◽  
Parameter Determination ◽  
Refractive Indices ◽  
Temperature Changes ◽  
Interferometric Technique ◽  
Anisotropic Fluids

Using a simple new interferometric technique, the ordinary and extraordinary refractive indices of the nematic liquid crystal p-ethoxybenzilidene-p-n-butylaniline have been measured separately as a function of temperature. Changes in the refractive indices have been measured with an accuracy of ±0.005% and the absolute values with an accuracy of ±0.5%. Thermal expansivity data has been obtained by utilizing a specially constructed thermometer containing the sample. By using a recently developed Clausius–Mossotti relation for anisotropic fluids, the effective molecular polarizability and hence the orientational order parameter have been obtained from refractive index and density measurements as a function of temperature.

Study of optical parameters of two fluorinated isothiocyanato nematic liquid crystals exhibiting high birefringence

2014 ◽  
Vol 22 (1) ◽  
Author(s):  
T. Devi ◽  
B. Choudhury ◽  
A. Bhattacharjee ◽  
R. Dabrowski
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Laser Beam ◽  
Order Parameter ◽  
Refractive Indices ◽  
Optical Parameters ◽  
Optical Studies ◽  
High Birefringence ◽  
Two Samples ◽  
Direct Extrapolation

AbstractOptical studies have been carried out on two fluorinated isothiocyanato nematic liquid crystal (LC) compounds 4′-butylcyclohexyl-3, 5-difluoro-4-isothiocyanatobiphenyl and 4′-pentylcyclohexyl-3, 5-difluoro-4-isothiocynatobiphenyl. Transition temperatures of the two samples were confirmed using a polarizing microscope. The two LC compounds were found to exhibit fairly high clearing temperatures. Measurements of refractive indices of the two compounds were done by using thin prism method with He-Ne laser beam of wavelength 630 nm. Birefringence of the two LC compounds was calculated from the measured refractive indices. Both the compounds are found to display fairly high values of birefringence. Validation of a modified four-parameter model, based on Vuks equation describing the temperature dependence of refractive indices of the two liquid crystals, is also presented in this paper. The model is validated by fitting the experimentally measured values of refractive indices, birefringence and average refractive indices of the two nematic LCs with the theoretical values. In this paper, the calculation of order parameters of the LCs is presented by using two methods: direct extrapolation method based solely on the birefringence data and by using modified Vuks method based on Haller’s extrapolation. As observed from the obtained results, this procedure of calculating order parameter gives very reasonable results.

Development of Low-Cost Abbe Refractometer

2018 ◽  
Vol 879 ◽  
pp. 227-233
Author(s):  
Weeratouch Pongruengkiat ◽  
Thitika Jungpanich ◽  
Kodchakorn Ittipornnuson ◽  
Suejit Pechprasarn ◽  
Naphat Albutt
Keyword(s):  
Refractive Index ◽  
Optical Materials ◽  
Low Cost ◽  
Optical Component ◽  
Refractive Indices ◽  
Constant Number ◽  
Optical Wavelength ◽  
Refractive Index Spectrum ◽  
Transparent Polymers ◽  
Abbe Refractometer

Refractive index and Abbe number are major physical properties of optical materials including glasses and transparent polymers. Refractive index is, in fact, not a constant number and is varied as a function of optical wavelength. The full refractive index spectrum can be obtained using a spectrometer. However, for optical component designers, three refractive indices at the wavelengths of 486.1 nm, 589.3 nm and 656.3 nm are usually sufficient for most of the design tasks, since the rest of the spectrum can be predicted by mathematical models and interpolation. In this paper, we propose a simple optical instrumental setup that determines the refractive indices at three wavelengths and the Abbe number of solid and liquid materials.

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