Nematic Liquid Crystals (NLC) Alignment by the Oriented Nanopatterns of some Polymers Functionalized with Monochlorotriazinyl-β-Cyclodextrin

2012 ◽  
Vol 20 ◽  
pp. 117-128
Author(s):  
Ana Maria Grigoriu ◽  
Constantin Luca ◽  
Aurelia Grigoriu ◽  
Cristina Racu ◽  
Gabriela Hitruc ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Uv Light ◽  
Nematic Liquid Crystals ◽  
Polarized Light ◽  
Hydroxyl Groups ◽  
Nanostructured Surfaces ◽  
Dichroic Dye ◽  
Vis Spectroscopy ◽  
Linearly Polarized ◽  
Ft Ir

This paper presents the practical strategies of obtaining the oriented nanostructured surfaces of some polymers functionalized with monochlorotriazinyl-β-cyclodextrin (MCT-β-CD) by two techniques: uniaxial rubbing or linearly polarized UV light (LPUVL) irradiation. We have chosen for the present study polymers and copolymers with exotic behavior with hydroxyl groups allowing the grafting of the reactive product monochlorotriazinyl-β-cyclodextrin or whose pyridinic nuclei can be complexated with MCT-β-CD. The obtained oriented nanostructures align colourless nematic liquid crystals (NLC) or NLC coloured with a dichroic dye. The orientation of NLC has been studied by means of polarized light FT-IR spectroscopy (IR dichroism) and polarized light UV-VIS spectroscopy (VIS dichroism). The initial polymers as well as the chemically modified products have an exotic behavior with regard to the ability of orientating the NLC. The polymers functionalized with MCT-β-CD orientate the NLC perpendicularly to the rubbing direction (or, for photopolymers, perpendicularly to the electrical vector of LPUVL).

Orientational Behaviour of some Novel Fluoro-Substituted Liquid Crystals as Studied by Optical Spectroscopy Methods

2011 ◽  
Vol 66 (3-4) ◽  
pp. 251-258 ◽  
Author(s):  
Anna Modlínska ◽  
Danuta Bauman ◽  
Jan Jadżyn ◽  
Roman Dąbrowski
Keyword(s):  
Liquid Crystals ◽  
Optical Spectroscopy ◽  
Orientational Order ◽  
Polarized Light ◽  
Emission Spectra ◽  
Dielectric Anisotropy ◽  
Dichroic Dye ◽  
Linearly Polarized ◽  
Orientational Distribution ◽  
Orientational Distribution Function

The long-range orientational order of eight newly synthesized fluoro-substituted liquid crystals, two with a positive dielectric anisotropy and six with a negative dielectric anisotropy, was studied by means of the optical spectroscopy methods: electronic absorption and fluorescence. The liquid crystals were doped with small amount of the fluorescent dichroic dye. The absorption and emission spectra of linearly polarized light were recorded as a function of temperature in the whole range of the mesophase. The results obtained allow to determine the order parameters〈P2 and〈P4〉as well as the orientational distribution function. An importance of the molecular structure of the liquid crystal on the orientational order was ascertained and discussed.

scholarly journals Synthesis, Fabrication, and Characterization of Functionalized Polydiacetylene Containing Cellulose Nanofibrous Composites for Colorimetric Sensing of Organophosphate Compounds

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1869
Author(s):  
A K M Mashud Alam ◽  
Donovan Jenks ◽  
George A. Kraus ◽  
Chunhui Xiang
Keyword(s):  
Solid State ◽  
Hydroxyl Groups ◽  
Colorimetric Sensing ◽  
Electrospinning Technique ◽  
Hazardous Chemical ◽  
Tensile Tester ◽  
Vis Spectroscopy ◽  
Ft Ir ◽  
Landmark Study

Organophosphate (OP) compounds, a family of highly hazardous chemical compounds included in nerve agents and pesticides, have been linked to more than 250,000 annual deaths connected to various chronic diseases. However, a solid-state sensing system that is able to be integrated into a clothing system is rare in the literature. This study aims to develop a nanofiber-based solid-state polymeric material as a soft sensor to detect OP compounds present in the environment. Esters of polydiacetylene were synthesized and incorporated into a cellulose acetate nanocomposite fibrous assembly developed with an electrospinning technique, which was then hydrolyzed to generate more hydroxyl groups for OP binding. Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), Instron® tensile tester, contact angle analyzer, and UV–Vis spectroscopy were employed for characterizations. Upon hydrolysis, polydiacetylene esters in the cellulosic fiber matrix were found unaffected by hydrolysis treatment, which made the composites suitable for OP sensing. Furthermore, the nanofibrous (NF) composites exhibited tensile properties suitable to be used as a textile material. Finally, the NF composites exhibited colorimetric sensing of OP, which is visible to the naked eye. This research is a landmark study toward the development of OP sensing in a protective clothing system.

Studies Of Orientational Order Of Some Nematogens By Means Of Raman Scattering Spectroscopy

2004 ◽  
Vol 59 (7-8) ◽  
pp. 510-516 ◽  
Author(s):  
Ewa Chrzumnicka ◽  
Mirosław Szybowicz ◽  
Danuta Bauman
Keyword(s):  
Liquid Crystals ◽  
Raman Scattering ◽  
Orientational Order ◽  
Polarized Light ◽  
Molecular Structures ◽  
Raman Scattering Spectroscopy ◽  
Linearly Polarized ◽  
Scattering Spectra ◽  
Raman Scattering Spectra ◽  
Molecular Distribution Function

The orientational behaviour of some liquid crystals with various molecular structures was studied by means of the Raman scattering depolarization method. The Raman scattering spectra of linearly polarized light were recorded as a function of temperature in the nematic phase. On the basis of these spectra the order parameters 〈P2〉 and 〈P4〉 as well as the molecular distribution function were determined. The obtained data were compared with those estimated on the basis of polarized light absorption and emission measurements. The influence of the molecular structure on the orientational order of liquid crystals was discussed.

Synthesis, Photoisomerization and Thermo-Optic Property of Azo Optically Active Polymer

2010 ◽  
Vol 663-665 ◽  
pp. 41-44
Author(s):  
Chang Hong Ge ◽  
Feng Xian Qiu ◽  
Xiao Xian Gu ◽  
Dong Ya Yang
Keyword(s):  
Uv Light ◽  
Inorganic Materials ◽  
Optical Parameters ◽  
Chiral Reagent ◽  
Vis Spectroscopy ◽  
Optic Property ◽  
Order Of Magnitude ◽  
Ft Ir ◽  
Azo Chromophore ◽  
Thermal Volume Expansion

A novel azobenzene optically polymer (P-DA) was synthesized based on the azo chromophore molecule, chiral reagent L(-)-tartaric acid, acryloyl chloride and methacrylate. The P-DA was characterized by FT-IR, UV-Vis spectroscopy, 1H NMR, DSC and TGA. The P-DA had high thermal stability up to its glass-transition temperature (Tg) of 110 oC and 5 % heat weight loss temperature of 199 oC. The UV-induced trans/cis photoisomerization and reflex-isomerization behaviors were investigated. The results indicated that the P-DA solution could undergo photochromism after irradiated by 365 nm UV light. The optical parameters: refractive index (n), the dielectric constant (ε) and thermal volume expansion coefficient (β) of P-DA were obtained. The thermo-optic coefficients are one order of magnitude larger than those of the inorganic materials, such as SiO2 (1.1×10−5 oC -1 and LiNbO3 (4×10−5 oC -1) and was larger than the organic material such as polystyrene (-1.23×10-4 oC -1) and PMMA (-1.20×10-4 oC -1). The conclusion had a little significance to develop optical communication.

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.

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