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

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.

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Jun-Yong Lee ◽  
Bohdan Lev ◽  
Jong-Hyun Kim

AbstractA carbon fibre is a rod-like microstructure, the longitudinal axis of which is aligned with the orientation of the director in a nematic liquid crystal. A nematic liquid crystal with negative dielectric anisotropy is mixed with carbon fibres. By applying an electric field perpendicular to the director, the carbon fibres tend to rotate in response to the electric field, and the directors around the carbon fibres tends to suppress the rotation. We control individual carbon fibres to obtain an expected orientation by handling the competition of two actions. The carbon fibre barely reacts in a small electric field. Meanwhile, when the threshold electric field is exceeded, the carbon fibre rotates with a steep gradient in the direction of the electric field. The change in the rotation shows little hysteresis. As the length of the carbon fibre is increased, the threshold electric field decreases. We analysed the above process with a theoretical model considering the response of the carbon fibre and liquid crystal. This study shows the possibility of accurate analogue orientation control of individual rod-like microstructures.


2010 ◽  
Vol 96 (1) ◽  
pp. 011106 ◽  
Author(s):  
Mamatha Nagaraj ◽  
Y. P. Panarin ◽  
U. Manna ◽  
J. K. Vij ◽  
C. Keith ◽  
...  

1972 ◽  
Vol 33 (C1) ◽  
pp. C1-63-C1-67 ◽  
Author(s):  
M. BERTOLOTTI ◽  
B. DAINO ◽  
P. Di PORTO ◽  
F. SCUDIERI ◽  
D. SETTE

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