Phase Transition, Birefringence and Orientational Order Parameter Studies in Four Members of Benzylidene Aniline Liquid Crystals

2011 ◽  
Vol 181-182 ◽  
pp. 115-119 ◽  
Author(s):  
P.V. Datta Prasad ◽  
G. Padmaja Rani ◽  
V.G.K.M. Pisipati
Keyword(s):  
Phase Transition ◽  
Order Parameter ◽  
Orientational Order ◽  
Orientational Order Parameter ◽  
Density Measurements ◽  
Smectic A ◽  
Anisotropic Field ◽  
Perfect Order ◽  
Density Values ◽  
Molecular Polarizabilities

The nature of the phase transitions across isotropic–nematic (IN) and nematic–smectic-A (N-SmA) are carried out using density measurements in N-(p-n-ethoxy benzylidene)-p-n-pentyl aniline, 2O.5, N-(p-n-methoxy benzylidene)-p-n-pentyloxy aniline, 1O.O5, N-(p-n-ethyl benzylidene)-p-n-dodecyl aniline, 2.12 and N-(p-n-butyl benzylidene)-p-n-dodecyl aniline, 4.12. The compounds exhibit IN, IN, IN and INSmA phase sequences respectively with varying thermal ranges suitable for the study of birefringence. The birefringence studies are carried out using Newton’s rings and wedge techniques which provide δn = (ne- no) (the birefringence) ne, and norespectively. The orientational order parameter, S is evaluated (i) directly from δn and Δn (the birefringence in perfect order), independent of the local field that the nematic molecule experiences and (ii) from molecular polarizabilities estimated from ne, noand density values assuming isotropic as well as anisotropic field that the nematic molecule experiences. The estimated order parameter from the different techniques is compared with one another and with the literature data.

Orientational order parameter estimated from molecular polarizabilities – an optical study

2012 ◽  
Vol 85 (1-2) ◽  
pp. 52-64 ◽  
Author(s):  
J. Lalitha Kumari ◽  
P.V. Datta Prasad ◽  
D. Madhavi Latha ◽  
V.G.K.M. Pisipati
Keyword(s):  
Order Parameter ◽  
Orientational Order ◽  
Orientational Order Parameter ◽  
Optical Study ◽  
Molecular Polarizabilities

scholarly journals Study of Molecular Polarizabilities and Orientational Order Parameter in the Nematic Phase of 6.O12O.6 and 7.O12O.7

2011 ◽  
Vol 01 (04) ◽  
pp. 167-174 ◽  
Author(s):  
Parameswara Rao Alapati ◽  
D. Bhuyan ◽  
D. Madhavi Latha ◽  
P. Pardhasaradhi ◽  
V. G. K. M. Pisipati ◽  
...  
Keyword(s):  
Order Parameter ◽  
Nematic Phase ◽  
Orientational Order ◽  
Orientational Order Parameter ◽  
Molecular Polarizabilities

Fluctuation-induced dielectric permittivity in the isotropic phase of cholesteric liquid crystals

2016 ◽  
Vol 30 (09) ◽  
pp. 1650053
Author(s):  
Prabir K. Mukherjee ◽  
Asok K. Das
Keyword(s):  
Experimental Data ◽  
Phase Transition ◽  
Dielectric Permittivity ◽  
Order Parameter ◽  
Orientational Order ◽  
Isotropic Phase ◽  
Orientational Order Parameter ◽  
Cholesteric Phase ◽  
Static Dielectric Permittivity ◽  
Temperature And Pressure

The temperature and pressure dependence of the static dielectric permittivity in the isotropic phase of the isotropic to cholesteric phase transition is calculated using Landau–de Gennes’s fluctuation theory, allowing spatial variation of the orientational order parameter. A comparison is made with experimental data available in the isotropic phase of the isotropic to cholesteric phase transition.

Optical Study of Orientational Order Parameter in p-n-(Phenyl Benzylidene) -p-Alkyl and Alkyloxy Anilines

2011 ◽  
Vol 181-182 ◽  
pp. 75-78 ◽  
Author(s):  
B.R. Rajeswari ◽  
P. Pardhasaradhi ◽  
M. Ramakrishna Nanachara Rao ◽  
P.V. Datta Prasad ◽  
D. Madhavi Latha ◽  
...  
Keyword(s):  
Order Parameter ◽  
Liquid Crystalline ◽  
Orientational Order ◽  
Molecular Vibration ◽  
Refractive Indices ◽  
Orientational Order Parameter ◽  
Optical Study ◽  
Shaped Cell ◽  
Scaling Methods ◽  
Molecular Polarizabilities

The refractive indices measurements are carried out using a modified spectrometer connected with wedge shaped cell and also the direct measurement of birefringence,δn obtained from Newton’s rings method with an indigenous setup for the liquid crystalline compoundsp-n-(phenyl benzylidene)-p-n-alkyl and alkyloxy anilines, PBnA and PBnOA compounds. The molecular polarizabilitiy anisotropy (α||- α⊥) is calculated for these compounds from different methods such as Lippincott δ-function model, molecular vibration method, Haller’s extrapolation method and scaling methods respectively. Further, the estimation of the molecular polarizabilities αeand αoare done from the isotropic Vuks and anisotropic Neugebauer models. The order parameter directly calculated from ∆n employing the method developed by Kuczynski is compared with the order parameter estimated from the different models using molecular polarizabilities.

Dielectric and orientational properties of nematogenic 4-n-octyl(4′-cyanophenyl)benzoate

2010 ◽  
Vol 18 (1) ◽  
Author(s):  
D. Bauman ◽  
J. Jadżyn ◽  
E. Wolarz ◽  
A. Modlińska ◽  
R. Dąbrowski
Keyword(s):  
Phase Transition ◽  
Relaxation Time ◽  
Dielectric Properties ◽  
Order Parameter ◽  
Orientational Order ◽  
Experimental Studies ◽  
Orientational Order Parameter ◽  
Dielectric Measurements ◽  
Frequency Range ◽  
Dichroic Dye

AbstractExperimental studies of the dielectric properties in the nematic and isotropic phases of 4-cyanophenyl-4′-n-octylbenzoate (8CPB) have been performed in the frequency range from 50 kHz to 100 MHz. The relaxation process related to the rotation around the short molecular axis has been analysed. The results obtained have revealed that in the vicinity of the I-N phase transition, the molecular subdiffusional rotation process occurs. It is connected with the pretransitional effects which are observed both in the static and dynamic dielectric measurements. On the basis of the temperature dependence of the relaxation time in the nematic and isotropic phases, the orientational order parameter 〈P2〉 has been determined. The values of 〈P2〉 obtained in this way have been compared with those evaluated from the measurements of the polarized electronic absorption of the dichroic dye, dissolved as guest probe in the mesogenic host.

Deuteron NMR investigation on orientational order parameter in polymer dispersed liquid crystal elastomers

2020 ◽  
Vol 22 (40) ◽  
pp. 23064-23072
Author(s):  
Andraž Rešetič ◽  
Jerneja Milavec ◽  
Valentina Domenici ◽  
Blaž Zupančič ◽  
Alexej Bubnov ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Order Parameter ◽  
Orientational Order ◽  
Orientational Order Parameter ◽  
Liquid Crystal Elastomer ◽  
H Nmr ◽  
Polymer Dispersed Liquid Crystal ◽  
Polymer Dispersed ◽  
Liquid Crystal Elastomers ◽  
Magnetically Aligned

Orientational order parameter of magnetically aligned liquid crystal elastomer particles suspended in a cured silicone matrix is assessed using 2H-NMR spectroscopy. Obtained results correspond well with the composite's thermomechanical response.

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.

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