Coefficients of molecular packing and intrinsic birefringence of aromatic polyimides estimated using refractive indices and molecular polarizabilities

2004 ◽  
Vol 42 (12) ◽  
pp. 2354-2366 ◽  
Author(s):  
Yoshiharu Terui ◽  
Shinji Ando
Keyword(s):  
Molecular Packing ◽  
Refractive Indices ◽  
Aromatic Polyimides ◽  
Molecular Polarizabilities ◽  
Intrinsic Birefringence

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 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.

scholarly journals Experimental Verification of Vuks Equation Using Hollow Prism Refractometer

2012 ◽  
Vol 2012 ◽  
pp. 1-6
Author(s):  
Anita Kanwar ◽  
Priya S. Yadav
Keyword(s):  
Liquid Crystal ◽  
Temperature Dependence ◽  
Experimental Verification ◽  
Cholesteric Liquid Crystal ◽  
Visible Range ◽  
Refractive Indices ◽  
Temperature Dependent ◽  
Crystalline Materials ◽  
Different Temperatures ◽  
Molecular Polarizabilities

The refractive indices of the cholesteric liquid crystal solution were measured using multiwavelength (visible range) refractometer for three different wavelengths. Measurements were made at different temperatures for various concentrations of the solution, mixing CLC in a soluble solvent. Vuks equation describes the wavelength and temperature dependence of refractive indices of anisotropic crystalline materials. We have used a simplified version of Vuks equation relating only to macroscopic indices and verified its validity for five-different-concentration solution at various temperatures. The result is also used to obtain molecular polarizabilities and temperature dependent material constants of our sample.

scholarly journals BIREFRINGENCE OF SPERMATOZOA

1972 ◽  
Vol 55 (2) ◽  
pp. 501-510 ◽  
Author(s):  
Irwin J. Bendet ◽  
James Bearden
Keyword(s):  
Refractive Index ◽  
Thermal Denaturation ◽  
The Other ◽  
Refractive Indices ◽  
Sperm Cells ◽  
Form Birefringence ◽  
Before And After ◽  
Bull Sperm ◽  
Influence Of Solvents ◽  
Intrinsic Birefringence

In thermal denaturation experiments on sperm cells, described in the accompanying paper, it was found that squid sperm, when melted, lose both birefringence and morphological shape. Bull sperm, on the other hand, show no change of morphology, but their initial negative birefringence becomes positive. Since this suggested the existence of form birefringence, the influence of solvents of different refractive indices on the observed birefringence was investigated, using a new derivation of the Wiener form birefringence equations which allows direct comparison of Wiener's theory with experimental results. Bull sperm showed form birefringence both before and after melting, while squid sperm showed none. Quantitative application of the general form of the Wiener equations to these results gave values for the refractive index and intrinsic birefringence of bull sperm cells. Application of the specific forms of the Wiener equations showed that neither of these descriptions of idealized systems was adequate to describe completely the form birefringence of bull sperm, but that the equation for platelike submicroscopic structures was more nearly an accurate fit to the data than that for rodlike structures.

The spindle stage: A powerful optical tool

1988 ◽  
Vol 46 ◽  
pp. 52-53
Author(s):  
Mickey E. Gunter ◽  
F. Donald Bloss
Keyword(s):  
Significant Error ◽  
Optical Data ◽  
Refractive Indices ◽  
Axis Of Rotation ◽  
Polarizing Microscope ◽  
Microscope Stage

A single, reasonably homogeneous, nonopaque 30-to-300 μm crystal, mounted on a spindle stage and studied by immersion methods under a polarizing microscope, yields optical data frequently sufficient to identify and characterize a substance unequivocally. The data obtainable include (1) the orientation of the crystal's principal vibration axes and (2) its principal refractive indices, to within 0.0002 if desired, for light vibrating along these principal vibration axes. Spindle stages tend to be simple and relatively inexpensive, some costing less than $50. They permit rotation of the crystal about a single axis which is parallel to the microscope stage. This spindle or S-axis is thus perpendicular to the M-axis, namely the microscope stage's axis of rotation.A spindle stage excels when studying anisotropic crystals. It orients uniaxial crystals within minutes and biaxial crystals almost as quickly so that their principal refractive indices - ɛ and ω (uniaxial); α, β and γ (biaxial) - can be determined without significant error from crystal misorientation.

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