Determination of phase transition temperatures in thermotropic liquid crystals by modulated optical transmission and thermal lens spectroscopy

2005 ◽  
Vol 125 ◽  
pp. 213-216 ◽  
Author(s):  
R. Mayén-Mondragón ◽  
J. M. Yánez-Limón
Keyword(s):  
Phase Transition ◽  
Liquid Crystals ◽  
Thermal Lens ◽  
Optical Transmission ◽  
Transition Temperatures ◽  
Thermal Lens Spectroscopy ◽  
Thermotropic Liquid Crystals ◽  
Phase Transition Temperatures

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).

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