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).

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.

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.

Determination of the liquid crystals phase transition temperatures using optical rotation effect

2011 ◽  
Vol 84 (11-12) ◽  
pp. 1028-1034 ◽  
Author(s):  
Xiao-ling Niu ◽  
Wei-guo Liu ◽  
Peng Liu ◽  
Chang-long Cai
Keyword(s):  
Phase Transition ◽  
Liquid Crystals ◽  
Optical Rotation ◽  
Transition Temperatures ◽  
Rotation Effect ◽  
Phase Transition Temperatures

scholarly journals On the Thermal Behaviour of the n·C13-n·C20 Lithium Soaps

1980 ◽  
Vol 35 (1) ◽  
pp. 98-102 ◽  
Author(s):  
P. Franzosini ◽  
M. Sanesi ◽  
A. Cingolani ◽  
P. Ferloni
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Thermal Behaviour ◽  
Room Temperature ◽  
Liquid Region ◽  
Transition Temperatures ◽  
Scanning Calorimetry ◽  
Isotropic Liquid ◽  
Phase Transition Temperatures

Abstract The phase transition temperatures and enthalpies were determined by differential scanning calorimetry between room temperature and the isotropic liquid region for the lithium n.alkanoates from tridecanoate to eicosanoate. The number and nature of the phases involved were discussed in comparison with the literature data available for some of the homologues concerned. For diffe-rent kinds of transitions, the significant features of the plots AS vs. number of carbon atoms were put into evidence.

scholarly journals Biobased Thermoplastic Elastomers: Structure-Property Relationship of Poly(hexamethylene 2,5-furanodicarboxylate)-Block-Poly(tetrahydrofuran) Copolymers Prepared by Melt Polycondensation

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 397
Author(s):  
Sandra Paszkiewicz ◽  
Izabela Irska ◽  
Agata Zubkiewicz ◽  
Anna Szymczyk ◽  
Elżbieta Piesowicz ◽  
...  
Keyword(s):  
Phase Transition ◽  
Shape Memory Polymer ◽  
Tensile Tests ◽  
Thermoplastic Elastomers ◽  
Sem Analysis ◽  
Transition Temperatures ◽  
Structure Property ◽  
Scanning Calorimetry ◽  
Molecular Weights ◽  
Phase Transition Temperatures

A series of poly(hexamethylene 2,5-furanodicarboxylate)-block-poly(tetrahydrofuran) (PHF-b-F-pTHF) copolymers were synthesized using a two-stage procedure, employing transesterification and polycondensation. The content of pTHF flexible segments varied from 25 to 75 wt.%. 1H nuclear magnetic resonance (NMR) and Fourier transformed infrared spectroscopy (FTIR) analyses were applied to confirm the molecular structure of the materials. Differential scanning calorimetry (DSC), dynamic mechanical measurements (DMTA), and X-ray diffraction (XRD) allowed characterizing the supramolecular structure of the synthesized copolymers. SEM analysis was applied to show the differences in the block copolymers’ morphologies concerning their chemical structure. The influence of the number of flexible segments in the copolymers on the phase transition temperatures, thermal properties, as well as the thermo-oxidative and thermal stability was analyzed. TGA analysis, along with tensile tests (static and cyclic), confirmed the utilitarian performance of the synthesized bio-based materials. It was found that an increase in the amount of pTHF caused the increase of both number-average and weight-average molecular weights and intrinsic viscosities, and at the same time causing the shift of the values of phase transition temperatures toward lower ones. Besides, PHF-b-F-pTHF containing 75 wt.% of F-pTHF units was proved to be a promising thermoplastic shape memory polymer (SMP) with a switching temperature of 20 °C.

Identification of phase transition temperatures by statistical image analysis

2012 ◽  
Vol 39 (6) ◽  
pp. 695-700 ◽  
Author(s):  
S. Sreehari Sastry ◽  
K. Mallika ◽  
B. Gowri Sankara Rao ◽  
Ha Sie Tiong ◽  
S. Lakshminarayana
Keyword(s):  
Phase Transition ◽  
Image Analysis ◽  
Transition Temperatures ◽  
Statistical Image Analysis ◽  
Phase Transition Temperatures
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