scholarly journals Transition Temperatures of Thermotropic Liquid Crystals from the Local Binary Gray Level Cooccurrence Matrix

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
S. Sreehari Sastry ◽  
T. Vindhya Kumari ◽  
C. Nageswara Rao ◽  
K. Mallika ◽  
S. Lakshminarayana ◽  
...  
Keyword(s):  
Phase Transition ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Optical Microscope ◽  
Gray Level ◽  
Transition Temperatures ◽  
Statistical Parameters ◽  
Thermotropic Liquid Crystals ◽  
Phase Transition Temperatures ◽  
Good Agreement

This paper presents a method which combines the statistical analysis with texture structural analysis called Local Binary Gray Level Cooccurrence Matrix (LBGLCM) to investigate the phase transition temperatures of thermotropicp,n-alkyloxy benzoic acid (nOBA,n=4,6,8,10and 12) liquid crystals. Textures of the homeotropically aligned liquid crystal compounds are recorded as a function of temperature using polarizing optical microscope attached to the hot stage and high resolution camera. In this method, second-order statistical parameters (contrast, energy, homogeneity, and correlation) are extracted from the LBGLCM of the textures. The changes associatedwiththe values of extracted parameters as a function of temperature are a helpful process to identify the phases and phase transition temperatures of the samples. Results obtained from this method have validity and are in good agreement with the literature.

scholarly journals Image Analysis Studies for Phase Transitions of Ferroelectric Liquid Crystals

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
S. Sreehari Sastry ◽  
B. Gowri Sankara Rao ◽  
K. B. Mahalakshmi ◽  
K. Mallika ◽  
C. Nageswara Rao ◽  
...  
Keyword(s):  
Phase Transition ◽  
Image Analysis ◽  
Liquid Crystals ◽  
Optical Microscope ◽  
Transition Temperatures ◽  
Scanning Calorimetry ◽  
Statistical Parameters ◽  
Ferroelectric Liquid Crystals ◽  
Phase Transition Temperatures ◽  
Parameter Values

Phase transition temperatures of ferroelectric liquid crystals ((S)-(-)-2-methylbutyl 4′-(4″-n-alkanoyloxybenzoyloxy) biphenyl-4-carboxylates (where n=16 and 18)) are studied through two techniques of image analysis. One is a statistical method, applied to compute the statistical parameters from the textures of each sample and the other, computation of Legendre moments being applied as image moment analysis, both of which are considered as a function of temperature. The textures of the samples are recorded with the polarizing optical microscope (POM) attached to the hot stage and high resolution camera. The phase transition temperatures of samples are inferred by the abrupt changes in the computed parameter values. The results obtained from the present methodology are in good agreement with those published in earlier literature done by the different techniques, like differential scanning calorimetry (DSC).

Synthesis and Mesomorphic Properties of a Series of Cholesteric Liquid Crystals

2010 ◽  
Vol 663-665 ◽  
pp. 759-762 ◽  
Author(s):  
Qing Lan Ma ◽  
Yuan Ming Huang
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Optical Microscopy ◽  
Scanning Calorimetry ◽  
Polarized Optical Microscopy ◽  
Phase Transition Temperatures ◽  
Second Category ◽  
Mesomorphic Properties

A series of cholesterol liquid crystal compounds was synthesized. Phase-transition temperatures and mesomorphic textures of these synthesized compounds were characterized with differential scanning calorimetry and polarized optical microscopy, respectively. In these molecules the terminal ester chains CnH2n-1COO-, where n was the number of carbon atoms in the terminal ester chains, were linked to the cholesterol core. All of the synthesized cholesterol compounds exhibited mesophases for the first heating. However, as temperature decreased from their clearing points, their micrographs can also be divided into two categories, the first category exhibits branch-like mesophase textures for n in the range of 1-10 while the second category exhibits branch-like crystal textures for n in the range of 11-18.

Electro-optical Kerr effect of nematic mixtures comprised of 6CHBT and 6BOBT

2008 ◽  
Vol 16 (4) ◽  
Author(s):  
H. Tajalli ◽  
A. Ghanadzadeh ◽  
H. Khoshsima ◽  
P. Zhalefar
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Order Phase Transition ◽  
Linear Dependence ◽  
Kerr Effect ◽  
Optical Kerr Effect ◽  
Transition Temperatures ◽  
Phase Transition Temperatures ◽  
Good Agreement ◽  
Second Order Phase Transition

AbstractStatic Kerr effect and the pre-transition temperature were investigated for the 6CHBT, 6BOBT and the nematic mixtures, M1 (40% 6CHBT: 60% 6BOBT), M2 (30% 6CHBT: 70% 6BOBT) and M3 (20% 6CHBT: 80% 6BOBT) at temperatures above the nematic-isotropic transition temperature. The linear dependence of (T-T*)−1 on the Kerr constant is found to be in good agreement with the predications of the Landau-De Gennes model. The hypothetical second order phase transition temperatures and susceptibility values were determined for these compounds.

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