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.

An Optical Study on Orientational Order Parameter and Molecular Polarizability in Benzylidene Anilines

2011 ◽  
Vol 181-182 ◽  
pp. 102-105 ◽  
Author(s):  
M. Ramakrishna Nanachara Rao ◽  
P.V. Datta Prasad ◽  
V.G.K.M. Pisipati ◽  
D. Madhavi Latha
Keyword(s):  
Order Parameter ◽  
Nematic Phase ◽  
Field Model ◽  
Orientational Order ◽  
Internal Field ◽  
Molecular Polarizability ◽  
Refractive Indices ◽  
Polarizability Anisotropy ◽  
Optical Study ◽  
Molecular Polarizabilities

Refractive indices measurements are carried out in four alkoxy benzylidene anilines viz., N-(p-n-methoxy and ethoxy benzaldehyde)-p-n-dodecyl and tetra decyl anilines, 1O.12, 1O.14, 2O.12 and 2O.14. First three compounds exhibit monovariant nematic phase while the last compound exhibits nematic and SmA phases with variable thermal ranges. The molecular polarizabilities are calculated from the refractive indices and the density using the well known internal field models by Vuks and Neugebauer. The molecular polarizability anisotropy is estimated from the Lippincott δ-function model as well as molecular vibrational methods. The order parameter is estimated using a) from the Haller’s extrapolation from molecular polarizabilities, b) from the scaling factors obtained from the equations by Vuks and Neugbeaur and c) directly from the birefringence - a method developed by Kuczynski et al without considering any internal field model to the liquid crystal molecule. The results evaluated from these methods are compared from one another and the limitations of the methods used are discussed.

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.

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

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.

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