Liquid Crystal In Nematic Phase Research Articles

Polarization characteristics of single-crystalline dichroic azo dye grown in nematic-phase liquid crystal

In this paper, we demonstrated the formation of single-crystalline dichroic dye which is grown in the nematic-phase liquid crystal as the solvent for molecular ordering control of dichroic dye molecules. The deposited microcrystals in parallel-aligned liquid crystal exhibited needle-like morphology and extinction position along the alignment direction of liquid crystal. We confirmed the deposited microcrystals were composed of only dichroic dye molecules. Structural evaluation by synchrotron X-ray diffraction indicated that dichroic dye molecules have a tilted angle on the substrate. We discuss the relation between the oriented structure of azo-based dichroic dye and their optical polarization characteristics for coatable polarizers utilizing crystalline-phase.

Dynamic Capacitance Changes by Flow Effect of Nematic-phase Liquid Crystals with Compressive Force

Dynamic Capacitance Changes by Flow Effect of Nematic-phase Liquid Crystals with Compressive Force

Paper] Systematic Investigation of Molecular Structure of Nematic-phase Liquid Crystals for Reduction of Dielectric Loss in Microwave Control Applications

Paper] Systematic Investigation of Molecular Structure of Nematic-phase Liquid Crystals for Reduction of Dielectric Loss in Microwave Control Applications

Structural analysis of benzothienobenzothiophene-based soluble organic semiconducting crystals grown by liquid crystal solvent

In this study, we analyzed organic semiconducting single crystals composed of benzothienobenzothiophene derivatives (2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene, C8-BTBT) grown by nematic-phase liquid crystal (LC) solvent. As a result, we clarified that the crystal b-axis direction of the C8-BTBT single crystals was consistent with the LC alignment direction. By optical evaluation and simulation based on density functional theory, we found that the C8-BTBT single crystals in LC solvent exhibited a novel molecular conformation having alkyl chains oriented toward the b-axis.

The inherent dynamics of isotropic- and nematic-phase liquid crystals.

The geodesic (shortest) pathways through the potential energy landscape of a liquid can be thought of as defining what its dynamics would be if thermal noise were removed, revealing what we have called the "inherent dynamics" of the liquid. We show how these inherent paths can be located for a model liquid crystal former, showing, in the process, how the molecular mechanisms of translation and reorientation compare in the isotropic and nematic phases of these systems. These mechanisms turn out to favor the preservation of local orientational order even under macroscopically isotropic conditions (a finding consistent with the experimental observation of pseudonematic domains in these cases), but disfavor the maintenance of macroscopic orientational order, even in the nematic phase. While the most efficient nematic pathways that maintain nematic order are indeed shorter than those that do not, it is apparently difficult for the system to locate these paths, suggesting that molecular motion in liquid-crystal formers is dynamically frustrated, and reinforcing the sense that there are strong analogies between liquid crystals and supercooled liquids.

固体的特性を有するスメクティック液晶のエレクトロレオロジー(<小特集>非ニュートン性,機能性を示す複雑流体の流動と応用)

The ER characteristics of a liquid crystal (8 CB) in smectic-A phase were investigated utilizing a parallel-plate rheometer under a stress control mode. The steady flow properties and solid like behavior of the liquid crystal under DC or AC electric fields were examined. Although the liquid crystal in nematic phase under steady shear flow showed the normal ER effect, i.e. increase in apparent viscosity under electric field, the viscosity in smectic phase exhibited an opposite effect in low shear rate region. Moreover, Bingham-like properties were observed in smectic phase and the yield stress obtained was affected by the electric field. When the electric field strength was low, the yield stress was almost the same as that obtained under no electric field. Above a threshold of DC electric field, the yield stress increased and then became constant. An opposite tendency was observed under AC electric fields. It appears that the smectic poly-domain structure is maintained under lower electric field conditions and has become more orderly and stronger under higher DC electric fields. By contrast, the AC electric field would generate more slippery layered structure because of the alternating electrical current on the molecules.

Optical aberration correction by real-time holography in liquid crystals

We present results of experiments that use nematic-phase liquid crystal as a real-time holographic recording medium. Plane-wave gratings were written with as little as 10 mJ/cm(2) of incident write-beam energy from a pulsed Nd:YAG laser, and diffraction efficiencies greater than 25% were measured at 633 nm. Grating decay times were observed to fall within two distinct time regimes: a rapid-decay time of 60 to 100 microsec and a slower-decay time of 6 to 30 msec. The rapid-decay regime was used to demonstrate real-time correction of severely aberrated images by degenerate four-wave mixing.

Refractive Indices and Orientational Order Parameter of Five Liquid Crystals in Nematic Phase

Abstract Refractive indices of bis-(4′-n-alkyloxy benzal)-2-chloro-1,4 phenylene diamine (alkyl = hexyl, octyl and decyl), RO-TN-101 and RO-CE-154 have been measured over the whole nematic ranges for different wave lengths. A prism method has been employed for these measurements. The samples were aligned by surface rubbing and by the application of magnetic field. For all the samples, the refractive index for the extra-ordinary ray (ne ) decreases and that for the ordinary ray (no) increases with increasing temperature. At the nematic isotropic transition there is a discontinuity in the refractive indices values. The principal molecular polarizabilities (αe and αo) for the samples have been calculated using Neugebauer's relation. The necessary density measurements have been made by us. The anisotropy of the molecular polarizabilities was calculated using Haller's extrapolation method. The orientational order parameters were calculated at different temperatures for the samples using principal polarizability and the molecular polarizability anisotropy values. The agreement with Maier-Saupe theory is quite good for all substances except RO-TN-101 which is a mixture.

Free-induction nuclear-magnetic-resonance line shapes of various liquid-sample configurations and the diffusion constant of a liquid crystal by spin echo

Expressions are derived which describe the line shape of magnetization due to the nuclear magnetic moments of a sample placed in a large homogeneous constant magnetic field (H0) with a small magnetic field gradient (G) superimposed on the constant field. The study of the diffusion constant by the spin-echo technique basically involves the superposition of a magnetic field gradient on the constant magnetic field. Therefore, the precise measurement of the magnitude of the magnetic field gradient is required in order to deduce the diffusion constant accurately. The line shape of the free-induction nuclear-resonance signal depends not only on the magnetic field gradient, but also on the shape of the sample holder. Line shapes for spherical, cylindrical, and cubic sample holders were derived and experimentally verified by the free-induction nuclear magnetic resonance of protons in water. Magnitudes of the magnetic field gradients were obtained precisely from the line shape of the free-induction signal. Using the spin-echo technique, the diffusion constant of p-methoxybenzylidene-p′-n-butylaniline (MBBA), a liquid crystal in nematic phase, was measured at room temperature.