OPTICAL ANISOTROPY AND FOUR POSSIBLE ORIENTATIONS OF A NEMATIC LIQUID CRYSTAL ON THE SAME FILM OF A PHOTOCHROMIC CHIRAL SMECTIC POLYMER

2000 ◽  
Vol 09 (01) ◽  
pp. 1-10 ◽  
Author(s):  
LEV M. BLINOV ◽  
RICCARDO BARBERI ◽  
MIKHAIL V. KOZLOVSKY ◽  
VLADIMIR V. LAZAREV ◽  
MARIA P. DE SANTO
Keyword(s):  
Liquid Crystal ◽  
Visible Light ◽  
Nematic Liquid Crystal ◽  
Optical Anisotropy ◽  
Liquid Crystalline ◽  
Uv Light ◽  
Glassy State ◽  
Electric Vector ◽  
Exciting Light ◽  
Linearly Polarized

Spin coated films of a chiral comb-like liquid crystalline copolymer containing azobenzene chromophores in its side chains are optically isotropic in their twisted smectic-like glassy state. In contact with a nematic liquid crystal (5CB, E7, MBBA) they provide a degenerate planar orientation. When irradiated by unpolarized UV light, they orient the same nematics homeotropically. Treated with linearly polarized UV light they orient nematics homogeneously with the director along the electric vector of the exciting light. After a combined irradiation first with unpolarized UV light and then with linearly polarized visible light, the films again provide a homogeneous liquid crystal orientation, this time with the director perpendicular to the visible light electric vector. The phenomena observed are related to the light induced optical anisotropy. Two main processes are responsible for the anisotropy (1) a UV light depletion of trans-isomers of the azobenzene chromophores from the chosen direction and (2) a reorientation of the chromophores by polarized visible light.

Liquid Crystal Alignment on Photoreactive Side-Chain Liquid-Crystalline Polymer Generated by Linearly Polarized UV Light

1997 ◽  
Vol 30 (21) ◽  
pp. 6680-6682 ◽  
Author(s):  
Nobuhiro Kawatsuki ◽  
Hiroshi Ono ◽  
Hirohumi Takatsuka ◽  
Tohei Yamamoto ◽  
Osamu Sangen
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystalline Polymer ◽  
Liquid Crystalline ◽  
Uv Light ◽  
Crystalline Polymer ◽  
Side Chain ◽  
Liquid Crystal Alignment ◽  
Linearly Polarized ◽  
Crystal Alignment

P-Cyanoazobenzene as a command molecule for azimuthal anisotropy regulation of a nematic liquid crystal upon exposure to linearly polarized visible light

Langmuir ◽  
1993 ◽  
Vol 9 (3) ◽  
pp. 857-860 ◽  
Author(s):  
Kunihiro Ichimura ◽  
Yuko Hayashi ◽  
Yuji Kawanishi ◽  
Takahiro Seki ◽  
Takashi Tamaki ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Visible Light ◽  
Nematic Liquid Crystal ◽  
Azimuthal Anisotropy ◽  
Linearly Polarized

Electro-optical property of polymerized liquid crystal devices using linearly polarized UV irradiation

2021 ◽  
Author(s):  
Masahiro Ito ◽  
Kazuma Kajiwara ◽  
Kohki Takatoh
Keyword(s):  
Liquid Crystal ◽  
Uv Light ◽  
Strong Dependence ◽  
Fast Response ◽  
Alignment Layer ◽  
Liquid Crystal Devices ◽  
Decay Times ◽  
Linearly Polarized ◽  
Reactive Mesogens ◽  
Strong Anchoring

Abstract Display characteristics have a fairly strong dependence on the configuration of the liquid crystal (LC) molecules and interactions between the LC molecules and the alignment layer surface. To obtain LC devices with a fast response, the usage of reactive mesogens (RMs) have been studied. RMs polymerize in the vicinity of the alignment layer. We assessed the effectiveness of linearly polarized UV light for polymer formation. Three kinds of UV light, namely (i)non-polarized (ii)parallel to, and (iii)perpendicular to the rubbing direction, were used to irradiate LC cells with RM concentrations of 5wt% and 10wt%. For both RM concentrations, LC devices using LPUV parallel to the rubbing direction yielded the shortest decay times. SEM observation revealed that the fibrils polymerized linearly in the same direction on using LPUV parallel to the rubbing direction. The decay time was presumably shortened by the strong anchoring force and high alignment ability of the linear fibrils.

scholarly journals Engineering Achiral Liquid Crystalline Polymers for Chiral Self-Recovery

2021 ◽  
Vol 22 (21) ◽  
pp. 11980
Author(s):  
Tengfei Miao ◽  
Xiaoxiao Cheng ◽  
Yilin Qian ◽  
Yaling Zhuang ◽  
Wei Zhang
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystalline ◽  
Uv Light ◽  
Helical Structure ◽  
Side Chain ◽  
Liquid Crystal Polymers ◽  
Polymeric Liquid ◽  
Crystalline Polymers ◽  
Liquid Crystal System ◽  
And Storage

Flexible construction of permanently stored supramolecular chirality with stimulus-responsiveness remains a big challenge. Herein, we describe an efficient method to realize the transfer and storage of chirality in intrinsically achiral films of a side-chain polymeric liquid crystal system by combining chiral doping and cross-linking strategy. Even the helical structure was destroyed by UV light irradiation, the memorized chiral information in the covalent network enabled complete self-recovery of the original chiral superstructure. These results allowed the building of a novel chiroptical switch without any additional chiral source in multiple types of liquid crystal polymers, which may be one of the competitive candidates for use in stimulus-responsive chiro-optical devices.

scholarly journals Mechanisms of Chiral Transfer in Optically Active Dopant – Nematic Liquid Crystal Systems

2020 ◽  
Vol 20 (4) ◽  
pp. 6-26
Author(s):  
V. A. Burmistrov ◽  
V. V. Aleksandriiskii ◽  
I. V. Novikov ◽  
O. I. Koifman
Keyword(s):  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Self Assembly ◽  
Liquid Crystalline ◽  
High Efficiency ◽  
Stationary Phases ◽  
Theoretical Description ◽  
Optically Active ◽  
Axial Coordination ◽  
Chiral Dopants

Induction of helical mesophases by incorporating chiral dopants into the nematics matrix is the promising modern trends in the chemistry of liquid crystals. This process is associated with a unique phenomenon - an amplification of chirality in liquid-crystalline phases, which ensures the detection of enantiomers by their chiral induction, much more sensitive than other methods. The relevance of this approach is due to the need to create perspective electro-optical devices operating with ultra-low control voltages based on twist effects, chromatographic stationary phases with high chiral selectivity, flexible magnets, photo-sensitive nanostructures, and other smart LC materials. The successful solution of these problems is impossible without experimental research and theoretical comprehension of the mechanisms of third level chiral transfer optically active dopant – nematic liquid crystal. In the last decade, a large number of works have appeared on the solution of these problems. This review is devoted to a generalization of the experimental results and a theoretical description of the transfer of molecular chirality to orientationally ordered systems with the participation of both chiral molecular substituents with an asymmetric carbon atom and planar or quasi-planar fragments chirally distorted relative to each other. The stereochemical aspects of induction associated with the structural correspondences of the dopant and nematic liquid crystal, as well as the main classes of optically active additives, are discussed. Application of metal complexes, both Werner and macroheterocyclic, are presented. Special attention is paid to the results of the mechanisms study of chiral transfer due to various intermolecular interactions: hydrogen bonding, axial coordination, and the formation of inclusion compounds. The high efficiency of induction of spiral mesophases has been demonstrated with a combination of different self-assembly mechanisms in liquid crystal - chiral additive systems.

Application of Dynamic Masking on Rapid Prototyping

2008 ◽  
Vol 594 ◽  
pp. 261-272
Author(s):  
Chien Nan Chen ◽  
Sheng Jye Hwang ◽  
Huei Huang Lee ◽  
Durn Yuan Huang
Keyword(s):  
Material Processing ◽  
Liquid Crystal ◽  
Rapid Prototyping ◽  
Visible Light ◽  
Laser Scanning ◽  
Uv Light ◽  
Liquid Crystal Display ◽  
Digital Light Processing ◽  
Uv Curable ◽  
Main Components

In rapid prototyping (RP) technologies, curing of UV-curable photopolymers is mainly achieved by the application of laser scanning with limited fabrication speed. The dynamic masking approach can improve the fabrication speed; however, current researches and available systems cure photopolymers with visible light rather than UV light. In this research, we have attempted to develop a UV dynamic masking RP system by implementing digital micro-mirror device (DMD) from digital light processing (DLP) technology and TFT liquid crystal display (LCD) panel. A DLP projector was disassembled and the main components were then recombined to form a dynamic mask generator. Thus, this study has shown the feasibility of obtaining a UV dynamic masking RP system that may be integrated for a UV-curable material processing.

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