The Determination of Elastic Constants in Weakly Birefringent Liquid Crystals

1985 ◽  
pp. 415-422
Author(s):  
Donald B. Dupré ◽  
Jacob R. Fernandes
Keyword(s):  
Liquid Crystals ◽  
Elastic Constants

Numerical investigation of influence of ionic space charge and flexoelectric polarization on measurements of elastic constants in nematic liquid crystals

2009 ◽  
Vol 17 (2) ◽  
Author(s):  
M. Buczkowska ◽  
G. Derfel ◽  
M. Konowalski
Keyword(s):  
Magnetic Field ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
External Magnetic Field ◽  
Space Charge ◽  
Elastic Constants ◽  
High Concentration ◽  
Light Passing ◽  
The Magnetic Field

AbstractDeformations of nematic layers caused by magnetic field allow determination of the elastic constants of liquid crystal. In this paper, we simulated numerically the deformations of planar and homeotropic nematic layers. The flexoelectric properties of the nematic and presence of ions were taken into account. Our aim was to show the influence of flexoelectricity on the results of the real measurement of the elastic constants k33 and k11. In these simulations, we calculated the optical phase difference ΔΦ between the ordinary and extraordinary rays of light passing through the layer placed between crossed polarizers as a function of the magnetic field induction B. One of the elastic constants can be calculated from the magnetic field threshold for deformation. The ratio k33/k11 can be found by means of fitting theoretical ΔΦ(B) dependence to the experimental results. The calculations reveal that the flexoelectric properties influence the deformations induced by the external magnetic field. In the case of highly pure samples, this may lead to false results of measurement of the elastic constants ratio k33/k11. This influence can be reduced if the nematic material contains ions of sufficiently high concentration. These results show that the flexoelectric properties may play an important role, especially in well purified samples.

The Determination of the Elastic Constants of Nematic Liquid Crystals

1976 ◽  
Vol 37 (1) ◽  
pp. 269-280 ◽  
Author(s):  
W. H. De Jeu ◽  
W. A. P. Claassen ◽  
A. M. J. Spruijt
Keyword(s):  
Liquid Crystals ◽  
Elastic Constants ◽  
Nematic Liquid Crystals

Automated determination of n-cyanobiphenyl and n-cyanobiphenyl binary mixtures elastic constants in the nematic phase from molecular simulation

2020 ◽  
Vol 5 (6) ◽  
pp. 1131-1136
Author(s):  
Jiale Shi ◽  
Hythem Sidky ◽  
Jonathan K. Whitmer
Keyword(s):  
Liquid Crystals ◽  
Molecular Simulation ◽  
Elastic Properties ◽  
Binary Mixtures ◽  
Elastic Constants ◽  
Nematic Phase ◽  
New Techniques ◽  
New Applications ◽  
Automated Determination

This work explores new techniques in molecular simulation which can be used to precisely determine and engineer elastic properties of liquid crystals for new applications.

Bestimmung elastischer Konstanten von MBBA und EBBA mit der elektrischen Leitfähigkeitsmethode / Determination of the Elastic Constants of MBBA and EBBA by Electric Conductivity Measurements

1975 ◽  
Vol 30 (4) ◽  
pp. 515-518 ◽  
Author(s):  
M. Greulich ◽  
G. Heppke ◽  
F. Schneider
Keyword(s):  
Magnetic Susceptibility ◽  
Liquid Crystals ◽  
Temperature Dependence ◽  
Electric Conductivity ◽  
Elastic Constants ◽  
Nematic Liquid Crystals ◽  
Elastic Behaviour ◽  
Conductivity Measurements

Abstract Several methods of studying the elastic behaviour of nematic liquid crystals by means of measuring the electric conductivity are discussed. The temperature dependence of the ratio of the splay and bend elastic constants to the anisotropy of the magnetic susceptibility is determined for N-(p-methoxybenzylidene) -p-n-butylaniline (MBBA), N-(p-ethoxybenzylidene) -p-n-butylaniline (EBBA) and mixtures of both.

Magnetism and liquid crystals

1987 ◽  
Vol 65 (10) ◽  
pp. 1185-1193 ◽  
Author(s):  
A. J. Dekker
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Liquid Crystals ◽  
Magnetic Anisotropy ◽  
Elastic Constants ◽  
Landau Theory ◽  
Anisotropy Field ◽  
Isotropic Phase ◽  
Magnetic Field Effects

Superficial similarities and essential differences between nematic liquid crystals and magnetically ordered systems as well as some magnetic-field effects in nematics are recalled. Magnetic anisotropy, field alignment, and the determination of elastic constants of nematics are discussed briefly. Landau theory is used to discuss the effect of a magnetic field on the nematic-isotropic phase transition; the predictions are compared with experiment.

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