scholarly journals Photo-Orientation of Liquid Crystals on Azo Dye-Containing Polymers

Polymers ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 159
Author(s):  
István Jánossy ◽  
Tibor Tóth-Katona
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Azo Dye ◽  
Mutual Influence ◽  
Polymer Interfaces ◽  
Rigid Core ◽  
Crystal Polymer ◽  
Orientation Process ◽  
Photosensitive Polymer ◽  
Disperse Red 1

In this communication, we summarise our results related to light-induced orientational phenomena at liquid crystal–polymer interfaces. We investigated photoalignment for various nematics at the interface with the photosensitive polymer layer polymethyl methacrilate functionalised with azo dye Disperse Red 1. It was found that the efficiency of photoalignment exhibits marked differences depending on the structure of the rigid core of the liquid crystal molecules. It was demonstrated that the photo-orientation process is also significantly affected by the type of mesophase in which irradiation is carried out. The observations highlight the importance of the mutual influence of the polymer and the liquid crystal in light-induced processes.

Effect of Photo-Isomerization of Azo Dyes on the Photonic Bandgap in Chiral Nematics

2011 ◽  
Vol 181-182 ◽  
pp. 257-260
Author(s):  
David Statman ◽  
Andrew Jockers ◽  
Daniel Brennan
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Azo Dyes ◽  
Azo Dye ◽  
Photonic Bandgap ◽  
Methyl Red ◽  
Central Wavelength ◽  
Chiral Nematic ◽  
Anchoring Energy ◽  
Pitch Length

Chiral nematic liquid crystals prepared with Grandjean texture demonstrate a photonic bandgap whose central wavelength is proportional to the pitch length, P, of the liquid crystal and whose width is given by (ne – no)P. We show that methyl red doped chiral nematics undergo a shift in the photonic bandgap upon photo-isomerization. This shift is a result of (1) photo-induced change in anchoring energy on the nematic surface, and (2) change in the natural pitch length from the photo-isomerization of the azo dye.

Photo-alignment of liquid crystals in micro capillaries with point-by-point irradiation

2014 ◽  
Vol 22 (3) ◽  
Author(s):  
A. Siarkowska ◽  
M. Jóźwik ◽  
S. Ertman ◽  
T. Woliński ◽  
V. Chigrinov
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Azo Dye ◽  
Laser Light ◽  
Alignment Method ◽  
Uv Laser ◽  
Orientation Control ◽  
Photo Alignment

AbstractA photo-alignment method for micro capillaries based on the SD-1 azo-dye is demonstrated. In this work a liquid-crystal molecules aligning layer is created by point-by-point irradiation of the azo-dye film by using an UV laser light. The method opens up new possibilities for an improved molecules’ orientation control in both glass- and polymer-based photonic liquid crystal fibres.

scholarly journals Electrically Controlled Diffraction Grating in Azo Dye-Doped Liquid Crystals

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1051 ◽  
Author(s):  
Chuen-Lin Tien ◽  
Rong-Ji Lin ◽  
Chi-Chung Kang ◽  
Bing-Yau Huang ◽  
Chie-Tong Kuo ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Electric Fields ◽  
Azo Dye ◽  
Nematic Liquid Crystals ◽  
Polarized Light ◽  
Dielectric Anisotropy ◽  
Linear Effect ◽  
Periodic Distribution ◽  
The Difference

This research applies the non-linear effect of azo dye-doped liquid crystal materials to develop a small, simple, and adjustable beam-splitting component with grating-like electrodes. Due to the dielectric anisotropy and optical birefringence of nematic liquid crystals, the director of the liquid crystal molecules can be reoriented by applying external electric fields, causing a periodic distribution of refractive indices and resulting in a diffraction phenomenon when a linearly polarized light is introduced. The study also discusses the difference in the refractive index (Δn), the concentration of azo dye, and the rising constant depending on the diffraction signals. The experimental results show that first-order diffraction efficiency can reach ~18% with 0.5 wt % azo dye (DR-1) doped in the nematic liquid crystals.

Optical Responses of Azo Dye Doped Cholesteric Liquid Crystal-Polymer Composite System

2009 ◽  
Vol 511 (1) ◽  
pp. 85/[1555]-95/[1565]
Author(s):  
Vinita Dhulia ◽  
Gupta Sureshchandra J. ◽  
Pradnya Prabhu ◽  
Bhakti Yadav
Keyword(s):  
Liquid Crystal ◽  
Polymer Composite ◽  
Azo Dye ◽  
Composite System ◽  
Cholesteric Liquid Crystal ◽  
Liquid Crystal Polymer ◽  
Optical Responses ◽  
Crystal Polymer

Microsecond Time-Resolved Infrared Study of the Electric-Field-Induced Reorientation of Nematic Liquid Crystals. Part II: Dependence of the Motion of Liquid Crystals on the Applied Electric Field

1993 ◽  
Vol 47 (12) ◽  
pp. 2108-2113 ◽  
Author(s):  
Taeko I. Urano ◽  
Hiro-O Hamaguchi
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Electric Field ◽  
Applied Electric Field ◽  
Slow Component ◽  
Fast Component ◽  
Rigid Core ◽  
Time Resolved ◽  
Flexible Part ◽  
Reorientation Motion

The electric-field dependence of the reorientation motion of a nematic liquid crystal, 5CB (4- n-pentyl-4'-cyanobiphenyl), has been studied by microsecond time-resolved infrared spectroscopy. A rectangular pulsed electric field with a short pulse duration (2 ms) and a low repetition rate (5 Hz) was used to examine the liquid crystal (LC) response in a silicon cell. The motion of the rigid core part (the cyanobiphenyl group) of 5CB was monitored by the CN stretch band and that of the flexible part (the pentyl group) by the pentyl CH stretch band. The response of the LC to the pulsed electric field consists of two components, the slow component and the fast component. The slow component is common to the rigid core and the flexible parts of SCB. The voltage dependence of the slow component exhibits a clear threshold, indicating that this component corresponds to a cooperative motion of the 5CB molecules. The fast component is specific to the flexible part and shows exponential rise and decay behavior patterns. This observation suggests that the fast component corresponds to some noncooperative motions which are characteristic of the pentyl group. It is most likely that the internal rotation around the C(biphenyl)-C(pentyl) bond is responsible for the fast component. It is suggested that the LC molecules near the cell interface play a key role in the primary stage of the reorientation motion under an applied electric field.

NMR Characterization of Liquid Crystal—Polymer Interactions in Polymer-Dispersed Liquid Crystals

1997 ◽  
Vol 51 (11) ◽  
pp. 1639-1643 ◽  
Author(s):  
Peter A. Mirau ◽  
Mohan Srentvasarao
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Liquid Crystal Polymer ◽  
Butyl Methacrylate ◽  
Magic Angle ◽  
Crystal Polymer ◽  
Nmr Characterization ◽  
Polymer Dispersed Liquid Crystals ◽  
Polymer Dispersed ◽  
Polymer Interactions

Solid-state nuclear magnetic resonance (NMR) and optical microscopy have been used to study liquid crystal–polymer interactions in polymer-dispersed liquid crystals (PDLCs) composed of the E7 liquid crystal mixture and poly( n-butyl methacrylate) or poly(isobutyl methacrylate). As previously reported, the droplets adopt a bipolar configuration in the PDLCs using poly( n-butyl methacrylate) as the matrix material and a radial configuration in those using poly(isobutyl methacrylate). The NMR signals from the E7 cannot be detected in the bulk state by using magic angle spinning and cross-polarization because of its liquid-like properties. The E7 and the polymer signals are only weakly cross-polarized in 60:40 E7/poly( n-butyl methacrylate) PDLCs but are strongly cross-polarized in the PDLCs with poly(isobutyl methacrylate). We suggest that the differences are due to a change in the surface-anchoring conditions and that NMR spectroscopy may provide a molecular-level probe of the forces that control droplet configuration and the electro-optical properties of these materials.

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