Pretransitional behavior in the isotropic phase of a nematic liquid crystal with the transverse permanent dipole moment

2006 ◽  
Vol 124 (14) ◽  
pp. 144907 ◽  
Author(s):  
Malgorzata Janik ◽  
Sylwester J. Rzoska ◽  
Aleksandra Drozd-Rzoska ◽  
J. Zioło ◽  
Pawel Janik ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Permanent Dipole Moment ◽  
Isotropic Phase

scholarly journals Dissipative structures induced by photoisomerization in a dye-doped nematic liquid crystal layer

2018 ◽  
Vol 376 (2135) ◽  
pp. 20170382 ◽  
Author(s):  
I. Andrade-Silva ◽  
U. Bortolozzo ◽  
C. Castillo-Pinto ◽  
M. G. Clerc ◽  
G. González-Cortés ◽  
...  
Keyword(s):  
Phase Transition ◽  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Dissipative Structures ◽  
Input Power ◽  
Isotropic Phase ◽  
Crystal Layer ◽  
Liquid Crystal Layer ◽  
Nematic Liquid Crystal Layer ◽  
Interface Propagation

Order–disorder phase transitions driven by temperature or light in soft matter materials exhibit complex dissipative structures. Here, we investigate the spatio-temporal phenomena induced by light in a dye-doped nematic liquid crystal layer. Experimentally, for planar anchoring of the nematic layer and high enough input power, photoisomerization processes induce a nematic–isotropic phase transition mediated by interface propagation between the two phases. In the case of a twisted nematic layer and for intermediate input power, the light induces a spatially modulated phase, which exhibits stripe patterns. The pattern originates as an instability mediated by interface propagation between the modulated and the homogeneous nematic states. Theoretically, the phase transition, emergence of stripe patterns and front dynamics are described on the basis of a proposed model for the dopant concentration coupled with the nematic order parameter. Numerical simulations show quite a fair agreement with the experimental observations. This article is part of the theme issue ‘Dissipative structures in matter out of equilibrium: from chemistry, photonics and biology (part 2)’.

Viscosity coefficients in the isotropic phase of a nematic liquid crystal

1977 ◽  
Vol 38 (2) ◽  
pp. 159-162 ◽  
Author(s):  
P. Martinoty ◽  
F. Kiry ◽  
S. Nagai ◽  
S. Candau ◽  
F. Debeauvais
Keyword(s):  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Isotropic Phase ◽  
Viscosity Coefficients

Induction of orientational order in the isotropic phase of a nematic liquid crystal

2001 ◽  
Vol 64 (2) ◽  
Author(s):  
M. Simões ◽  
P. R. Fernandes ◽  
A. J. Palangana ◽  
S. M. Domiciano
Keyword(s):  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Orientational Order ◽  
Isotropic Phase

scholarly journals Dielectric and Electro-Optic Effects in a Nematic Liquid Crystal Doped with h-BN Flakes

Crystals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 123 ◽  
Author(s):  
Rajratan Basu ◽  
Lukas J. Atwood ◽  
George W. Sterling
Keyword(s):  
Liquid Crystal ◽  
Electric Field ◽  
Nematic Liquid Crystal ◽  
Hexagonal Boron Nitride ◽  
Honeycomb Structure ◽  
Dielectric Anisotropy ◽  
Isotropic Phase ◽  
Electro Optic ◽  
Anchoring Strength ◽  
Director Reorientation

A small quantity of hexagonal boron nitride (h-BN) flakes is doped into a nematic liquid crystal (LC). The epitaxial interaction between the LC molecules and the h-BN flakes rising from the π−π electron stacking between the LC’s benzene rings and the h-BN’s honeycomb structure stabilizes pseudo-nematic domains surrounding the h-BN flakes. Electric field-dependent dielectric studies reveal that the LC-jacketed h-BN flakes follow the nematic director reorientation upon increasing the applied electric field. These anisotropic pseudo-nematic domains exist in the isotropic phase of the LC+h-BN system as well, and interact with the external electric field, giving rise to a nonzero dielectric anisotropy in the isotropic phase. Further investigations reveal that the presence of the h-BN flakes at a low concentration in the nematic LC enhances the elastic constants, reduces the rotation viscosity, and lowers the pre-tilt angle of the LC. However, the Fréedericksz threshold voltage stays mostly unaffected in the presence of the h-BN flakes. Additional studies show that the presence of the h-BN flakes enhances the effective polar anchoring strength in the cell. The enhanced polar anchoring strength and the reduced rotational viscosity result in faster electro-optic switching in the h-BN-doped LC cell.

Carbon Nanotubes Blended Nematic Liquid Crystal for Display and Electro-Optical Applications

2021 ◽  
Vol 2 (4) ◽  
pp. 466-481
Author(s):  
Bhupendra Pratap Singh ◽  
Samiksha Sikarwar ◽  
Kamal Kumar Pandey ◽  
Rajiv Manohar ◽  
Michael Depriester ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Orientational Order ◽  
Isotropic Phase ◽  
Multi Walled Carbon Nanotubes ◽  
Vertically Aligned ◽  
Higher Temperature ◽  
Optical Applications ◽  
Walled Carbon Nanotubes

In this paper, we investigate a commercial nematic liquid crystal (LC) mixture namely E7 dispersed with small concentrations of multi-walled carbon nanotubes (MWCNTs). The dielectric and electro-optical characterizations have been carried out in the homogeneously and vertically aligned LC cells. The electro-optical response of LC molecules has been enhanced by 60% after the addition of MWCNTs, which is attributed to the reduced rotational viscosity in the composites. MWCNTs act like barricades for ionic impurities by reducing them up to ∼34.3% within the dispersion limit of 0.05 wt%. The nematic–isotropic phase transition temperature (TNI) of the E7 LC has also been shifted towards the higher temperature, resulting in a more ordered nematic phase. The enhanced birefringence and orientational order parameter in the LC-MWCNTs are attributed to π-π electron stacking between the LC molecules and the MWCNTs. The outlined merits of the LC-MWCNTs composites evince their suitability for ultrafast nematic-based electro-optical devices.

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