Papers by Keyword: Liquid Crystal

Abstract: In order to obtain an important azobenzene liquid crystal intermediate with phenylacetylene group, Sonogashira coupling reaction was used to preparation the compound. In this paper, the intermediate was synthesized by (4-Iodo-phenyl)-(4-trifluoromethyl-phenyl)-diazene and trimethyl silyl acetylene (TMSA) as raw materials, and then the trimethyl silyl group was removaled under the action of K₂CO₃. During the synthesis, the optimum reaction conditions were obtained, that the mol ratio of (4-Iodo-phenyl)-(4-trifluoromethyl-phenyl)-diazene and trimethyl silyl acetylene was 1:2, the reaction temperature was 80 oC. Fourier transform infrared spectroscopy (FT-IR) was used to measure the molecular structure of the target compound.

Abstract: An novel intermediate of (4-Iodo-phenyl)-(4-trifluoromethyl-phenyl)-diazene for azobenzene liquid crystal was synthesized. 4-Trifluoromethyl-phenylamine as raw material was oxidized by Oxone (Potassium peroxymonosulfate) in CH₂Cl₂/H₂O solvent to synthesize 1-Nitro-4-trifluoromethyl-benzene (m1). The effect of Oxone amount on the conversion degree of raw material was discussed in ditail. Then m1 was coupled with 4-Iodo-phenylamine to obtain the important intermediate, yellow solid, the yield was 52%. The chemical structures of synthetic intermediate was confirmed by FT-IR and 1H-NMR.

Abstract: Liquid crystals (LCs) are compounds that have properties between isotropic liquids and solid crystal materials. Although there is not a parameter to predict this behavior, the liquid crystals reported until now have common characteristics, for example rigid groups such as columns or rods within its structures, and long hydrocarbon chains that give flexibility. In this work we report the synthesis and characterization of LC N,N'-(1,4-phenylene bis (methanylylidene)) bis (4-(hexyloxy) aniline). The compound was characterized by infrared (IR), raman and ¹H-nuclear magnetic resonance (¹H-NMR) spectroscopies. The mesomorphic properties were determined by Differential Scanning Calorimetry (DSC) and Polarized Optical Microscopy (POM). The compound N,N'-(1,4-phenylene bis (methanylylidene)) bis (4-(hexyloxy) aniline) was obtained with a yield of 87 % and purity of 99.9 % determined by elementary analysis. The POM study revealed that this compound have a typical low molecular weight liquid crystal behavior. At temperatures of 157 and 174 °C typical mesophases of liquid crystals were observed; the phase transitions were analyzed by DSC. The POM images reveal the typical birefringence of liquid crystal behavior and different anisotropic textures of smectic and nematic mesophases, these textures are characteristic of the benzylideneanilines or Schiff bases.

Abstract: Cholesteryl ester liquid crystal was found to be non-toxic and it was recently applied as a cell traction force sensor. The reason for the affinity of the cells to this liquid crystal is unclear and required further investigation. This paper focused on determining the surface energy of the liquid crystals. A custom built contact angle measurement system and Fox-Zisman theory was applied to determine the critical surface tension of the cholesteryl ester liquid crystal. Eight different polar probe liquids were selected to determine the contact angle of the glass slides coated with cholesteryl ester liquid crystals. We found that the critical surface tension of the liquid crystal at 37.5 mN/m characterized the surface of the liquid crystal to be moderately hydrophobic. However, as reported in our previous work that the interaction of the liquid crystal and the cell culture media could re-orientate the amphiphilic molecules of the liquid crystals leading to the formation of lyotropic layers on the bulk cholesteric phase, therefore, making the surface to be hydrophilic. This then supported the formation of the hydrophilic layers that favors cell adhesion.

Abstract: High-Birefringence Nematic Liquid Crystals Mixtures (HBNLCM) recently developed in the Military University of Technology (Poland) are presented in this paper. Dielectric, refractometric, viscosimetric and elastomeric characteristic were determined. The properties are discussed in terms of their applicability to electro-optical devices. Applying HBNLCM of LCM to space mission (Phobos Ground) applications for a space-borne laser rangefinder was developed, manufactured and tested under cooperation between Military University of Technology (MUT) in Poland and Vavilov State Optical Institute (Vavilov SOI) in Russia. Transmission T of Liquid Crystal Cell (LCC) at λ=1.064 μm was not smaller than 95% at the aperture diameter not less than 15 mm. Switching on and switching off times in 2.5 μm thick LCC driven by voltage 10 V were not larger than 0.7 ms. Applying HBNLCM of LCM3 to refractive index matched twisted Nematic Liquid Crystal Cell of type LCNP4 for Thomson diagnostics of dense plasma was developed, manufactured and tested under cooperation between MUT in Poland and the National Research University of Information Technologies, Mechanics and Optics in Russia. Transmission T of LCNP4 at λ=1.064 μm was not smaller than 97% at the aperture diameter not less than 30 mm. Switching on time in 2.5 μm thick LCNP4 driven by voltage 200 V was not larger than 3 μs. LCNP4 can easily tolerate 0.42 J/cm².

Abstract: The electrically controlled birefringence of nematic liquid crystal BL-009 was measured by polarized interference method. The influence of LC absorption effect, the birefringence variation, is discussed in this paper. The experiments results showed the influence to birefringence is big in infrared region. Not only the birefringence value is greatly different with that of unconsidering absorption effect, but also the gradient changing of birefringence curves is obvious. Furthermore, the electrically controlled birefringences of two conditions are compared when the absorption coefficients of ordinary light and the extraordinary light are nearly same and greatly different. The analysis demonstrated the approximate method of absorption coefficient is feasible.

Abstract: In view of the extraction of liquid crystal from the wasted LCD panels, this paper aims to analyze the raw materials consumption, energy consumption and emissions to the environment in the extracting process based on the method of Life Cycle Assessment (LCA). The environmental impacts of the recycling procedure are assessed with the aid of LCIA（Life Cycle Inventory Assessment）method and CML2001 method provided by LCA analyzing software Gabi 4. Two ways of liquid crystal extraction mentioned in the paper are supercritical method and distilling method. The assessment results indicate: the supercritical method’s LCIA result is 3 times higher than the distilling method, but the liquid crystal extracting rate can reach 95% with a lower raw materials consumption; the environmental impacts of distilling method is lower than supercritical method, but its extracting rate of liquid crystal can only get to 50%. For industrial applications, supercritical method has greater advantages and there are more crafts to perfect for distilling method in improving the recovery rate of liquid crystal.

Abstract: Liquid crystals, contained in Liquid Crystal Display (LCD), would cause undesirable impacts on the environment and human health if not treated properly. Converting the waste liquid crystal into harmless product has aroused worldwide attention. In the present work, hydrothermal technology was applied to treat the liquid crystal of 4-octoxy-4'-cyanobiphenyl, which is one of the most common used liquid crystals in LCDs. The experiment was carried out in a 5.7 mL stainless tube reactor and heated by an oven. The effect of reaction temperature and reaction time on degradation rate was evaluated and the analysis was conducted with High Performance Liquid Chromatography (HPLC). The degradation products in liquid phase were analyzed with Gas Chromatography/Mass Spectrometer (GC/MS). Results indicate that the degradation rate improved along with the increase of reaction temperature and reaction time. At 300 C and with the reaction time of 90 min, 99.8% of 4-octoxy-4'-cyanobiphenyl could be degraded into simple and environmental innocuous products and its environmental risks were finally eliminated.

Abstract: Nonlinear light propagation in a dye-doped liquid crystal (LC) was investigated experimentally. A laser beam with wavelength far from the absorption peak of the material was coupled into an LC cell with homogeneous alignment, and the propagation in the cell was observed. When the polarization azimuth of the incident light was orthogonal to the orientation direction of the LC, soliton-like propagation was obtained for milliwatts of light power in spite of the low absorption. We clarified that the observed nonlinearity is due principally to the photothermal effect enhanced by the dye.

Abstract: The ability of a cell to adhere and transmit traction forces to a surface reveals the cytoskeleton integrity of a cell. Shear sensitive liquid crystals were discovered with new function in sensing cell traction force recently. This liquid crystal has been previously shown to be non-toxic, linear viscoelastic and sensitive to localized exerted forces. This paper reports the possibility of extending the application of the proposed liquid crystal based cell force sensor in sensing traction forces of osteoblast-like (MG-63) and human keratinocyte (HaCaT) cell lines exerted to the liquid crystal sensor. Incorporated with cell force measurement software, force distributions of both cell types were represented in force maps. For these lowly contractile cells, chondrocytes expressed regular forces (10 – 90 nN, N = 200) around the circular cell body whereas HaCaT projected forces (0 – 200 nN, N = 200) around the perimeter of poly-hedral shaped body. These forces are associated with the organisation of the focal adhesion expressions and stiffness of the LC substrate. From the results, liquid crystal based cell force sensor system is shown to be feasible in detecting forces of both MG63 and HaCaT.