Types Of Liquid Crystals Research Articles

ChemInform Abstract: Synthesis and Mesomorphic Properties of a Series of Phenyl 6‐(4‐Alkoxyphenyl)nicotinates.

Abstract5 New liquid crystals of type (III) are prepared with the ortho‐regioselective addition of Grignard reagents as the key step.

Highly efficient full-color display based on blue LED backlight and electrochromic light-valve coupled with front-emitting phosphors

We report a novel full-color display based on the generation of full-color by blue light approach, so called color-by-blue display. This newly proposed color-by-blue light-valve display combines a blue backlight excitation source, a blue light-valve shutter, and front-emitting phosphor pixels. Careful evaluation shows that the detailed display characteristics as well as excellent cycling durability under a low operation voltage of 3 V easily satisfy the requirements for the current display application. Also, we would like to emphasize that the proposed method shows a conversion efficiency of 20%, surpassing the value (≈5%) seen in the typical liquid crystal displays. Although the switching response reported here is slower than in a commercial display module due to the solution-phase electrochromic nature of the shutter used, a response time close to that of a liquid crystal display is highly feasible, as we suggest.

Synthesis of New Liquid Crystals with 2,3,4,9-Tetrahydro-1H-Fluorene Moiety

A new range of liquid crystals containing the 2,3,4,9-tetrahydro-1H-fluorene system have been prepared and its thermal properties were examined. The mesomorphic properties are compared with those of the fluorene and trans-cyclohexane derivatives. Introduction of 2,3,4,9-tetrahydro-1H-fluorene in typical liquid crystal structure leads to decrease of melting point and the clearing point values. The chemical structures and mesogenic properties for the reported novel compounds are discussed.

Analyzing small suprathreshold differences of LCD-generated colors

Small suprathreshold color differences around five CIE color centers were investigated on a typical liquid crystal display (LCD) with fluorescent backlight using the method of constant stimuli. The results were evaluated using probit analysis and compared with surface-color differences of the RIT-DuPont dataset. We focused especially on the relationship between T50 distances obtained from LCD and surface-color stimuli and on the influence of the display's narrowband primaries and its relatively low luminance level on interobserver uncertainty. The low luminance level of the LCD decreases the perceived color differences. However, considering the visual uncertainty of the experimental data, we could not reject the hypothesis that T50 distances from the RIT-DuPont and our experiment agree up to a constant scaling factor. In addition, we found significantly higher interobserver variability in the estimation of small color differences if the colors are viewed on an LCD. There are some indications that color-difference perception might be influenced by individual color-matching functions and, thus, by the spectral power distribution of the stimuli. We provide the experimental data, including all spectral stimuli shown to the observers, on our website.

Tunable photoluminescence of porous silicon by liquid crystal infiltration

The photoluminescence (PL) of porous silicon films has been investigated as a function of the amount of liquid crystal molecules that are infiltrated into the constricted geometry of the porous silicon films. A typical nematic liquid crystal 4-pentyl-4′-cyanobiphenyl was employed in our experiment as the filler to modify the PL of porous silicon. It is found that the originally red PL of porous silicon films can be tuned to blue by simply adjusting the amount of liquid crystal molecules in the microchannels of the porous films. The chromaticity coordinates are calculated for the recorded PL spectra. The mechanism of the tunable PL is discussed. Our results have demonstrated that the luminescent properties of porous silicon films can be efficiently tuned by liquid crystal infiltration.

NMR study of a phasmid-like liquid crystal

Carbon-13 NMR measurements of the chemical shifts are reported as a function of temperature for a semi-phasmidic molecule 4-(2,3,4-tridecyloxy-phenylazo)-benzoic acid (TDPABA). The data indicate a dimer structure in the solution and suggest a similar structure also in the nematic phase, which is consistent with it being a phasmid-like liquid crystal. The orientational order parameters are derived in the nematic phase based on the carbon shielding tensors calculated by Density Functional Theory. The nematic order parameter S zz is found to be (relatively) higher for TDPABA than that found in a typical calamitic liquid crystal, likely due to its underlying columnar phase.

반사형 쌍안정 카이랄 스플레이 네마틱 액정표시소자

Bistable chiral splay nematic liquid crystal display (BCSN LCD) is a memory type liquid crystal display using splay and twist states as two stable states. When the cell thickness to pitch (d/p) ratio is 0.25, splay and twist states have permanent memory time. However, when the transition from twist state to splay state is caused by a fringe field, pixel regions show that the splay state is not perfect, but rather includes a contribution from the twist state. In this paper, we propose a reflective BCSN LCD using twist state in which the two stable states do not coexist. The fabricated reflective BCSN LC cell shows a high contrast ratio of over 30:1 and response times of 950 ms and 450 ms in vertical and fringe field switching, respectively. The proposed cell also shows wide viewing angle characteristics of in left- and right directions.

Unique liquid crystal behavior in water of anionic fluorocarbon–hydrocarbon hybrid surfactants containing oxyethylene units

This study reports the unique aqueous lyotropic liquid crystal behavior of an anionic hybrid surfactant, 8F-B2ES, which has 2-[2-(butyloxy)ethyloxy]ethyl and 1H,1H,2H,2H-perfluorodecyl tails. An 8F-B2ES-analog hybrid surfactant with no oxyethylene units (8F-DeS) and a symmetric fluorinated double-tail surfactant with two 2-(1H,1H,2H,2H-perfluorohexyloxy)ethyl tails (4FEOS) were used as control surfactants in examining the effects of the oxyethylene units and of the hybrid structure on the liquid crystal behavior. Polarized microscopic observations showed the formation of a lamellar liquid crystal phase for each surfactant/water mixture at surfactant concentrations higher than 10wt.%. In the case of the 30wt.% 8F-B2ES/water mixture, two types of spherical aggregates were observed at temperatures higher than 40°C: one was a typical lamella liquid crystal with a maltese cross-texture, and the other was optically isotropic. Interestingly, when the 8F-B2ES lamellar phase was cooled to below 40°C, the lamellar aggregates were distorted and the isotropic droplets became anisotropic. As this unique liquid crystal behavior was not observed for aqueous mixtures of the control surfactants, the oxyethylene units in the hybridized hydrocarbon tail play an important role in the behavior. This study also examined the effect of the oxyethylene units on microenvironmental polarity in the hybrid surfactant bilayer via fluorescence spectral measurements of pyrene solubilized in each lamellar phase. The polarity of the 8F-B2ES bilayer at 70°C was found to be that of a hydrocarbon surfactant lamellar phase, and increased gradually with decreasing temperature. The polarity became the same as that of hydrophilic spherical micelles below 40°C, despite the presence of the lamellar aggregates. Since the polarity in the 8F-DeS bilayer was independent of temperature, and as low as that of a typical hydrocarbon surfactant bilayer, hydration of the 8F-B2ES oxyethylene units would increase the polarity, and then loosen the 8F-B2ES packing within the bilayer. This probably led to distortion of the lamellar aggregates.

Comparison of eye fatigue among readings on conventional book and two typical electronic books equipped with electrophoretic display and LC display

We have measured eye fatigue after each 90 minutes of reading on a paper (book), electronic paper (book reader using electrophoretic reflective display), and LCD (backlight type liquid crystal display). Increase of Near Point Distance was measured in each subject as an objective index. Subjective impression of eye fatigue was answered by subjects using fatigue scale of 5 ranks. As a result, the biggest fatigue was indicated by LCD while the smallest fatigue was indicated by a conventional paper book.

位相変調型液晶ディスプレイを用いた電子ホログラフィ

There are two types of hologram, an amplitude modulation and a phase modulation ones. Recently, not only amplitude modulation ones but also phase modulation ones have been used in liquid crystal displays. We constructed an electro-holography system with a phase modulation type liquid crystal display and compared it to a system using current amplitude electro-holography. In the amplitude hologram, the reconstructed image darkens because the contrast of the hologram is low when the gray level is increased. It lightens most when binary. However, the phase hologram with high diffraction efficiency has produced an excellent result. The reconstructed image is bright even if the gray level is increased, and all the information of the liquid crystal display can be used at 256 gray levels.

Photoluminescence of Liquid Crystal Infiltrated Porous Silicon Film

We have investigated the photoluminescence (PL) of a porous silicon film in which a typical nematic liquid crystal 4-pentyl-4’-cyanobiphenyl infiltrated. Before the liquid crystal filtration, the PL spectrum of the porous silicon film is comprised of two luminescent bands, one of which is located at about 600 nm whereas the other of which is located at about 450 nm. After the liquid crystal filtration, the porous silicon film gives off intense deep-blue PL with its peak located at about 400 nm at the cost of the complete quenching of the PL from the original porous silicon film. Our results have demonstrated that the luminescent properties of porous silicon films can be dramatically modified by liquid crystal infiltration.

Density Measurements and Thermodynamic Parameters of 4,4′-Dibutoxyazoxybenzene

Thermodynamic functions using the coefficient of volume expansion (α) of a system, a number of thermoacoustic and anharmonic parameters such as the isochoric temperature coefficient of internal pressure (X), isochoric temperature coefficient of volume expansivity (X′), reduced compressibility (β∼), reduced volume (V ∼), isothermal microscopic Gruneisen parameter (Γ), fractional free volume (f), and Sharma parameter (So) can be investigated. The temperature dependence of these parameters gives a basic understanding about the intermolecular interactions in general. These studies also can applied to a solute in dilute solutions. In the present study these different parameters have been determined using volumetric measurements in the case of a liquid crystal, namely, 4,4′-dibutoxy azoxy benzene (HPOAB), which is a typical liquid crystal with a nearly linear structure, in dilute solutions at different temperatures. Variations in various parameters with respect to temperature are discussed in the light of the results obtained. The variation of the properties is analyzed and discussed in this article.

Self-phase modulation and ring pattern observation by applying electrical field on dye-doped nematic liquid crystal

In this work, we report the experimental results of two typical liquid crystals (6CHBT and w1680) in the nematic phase while they have been doped with Sudan dyes compared with pure state. We investigate the AC-applied voltage effect on the nonlinear behavior of dye doped liquid crystal (DDLC). The novel effects on the far-field diffraction patterns of a Gaussian beam depend on the external applied field. The measurements were performed using CW He:Ne laser and Nd:Yag laser at 632.8 nm and 532 nm, respectively. The z-scan technique is used to measure the amplitude and the sign of the nonlinear refractive indices DDLC. The nonlinear refractive indices were in order of 10 − 5 cm 2/W. Also the nonlinear absorption coefficient β was measured using open aperture z-scan technique.

Piezoelectricity of phospholipids: Are cell membranes also piezoelectric?

Recently it was foundi that mechanical deformation of films of L-α-phosphatidylcholine in the La phase induces an electric polarization. It was suggested that this effect is due to the chiral smectic A (SmA∗) type liquid crystal structure of the bilayers, which under molecular tilt becomes a ferroelectric (SmC∗) phase, where the electric polarization is normal to the tilt plane. However no control measurement on the racemic material has been presented to prove this suggestion. Here we demonstrate that indeed the chirality of phospholipids makes fluid lipid bilayers piezoelectric. By periodically shearing and compressing nonaqueous lamellar phases of synthetic right enantiomer 2,3-Dihexadecanoyl-sn-glycero-1-phosphocholine (D-DPPC) the synthetic left enantiomer 1,2-Dihexadecanoyl-sn-glycero-3-phosphocholine (L-DPPC) lipids and their racemic mixture (DL-DPPC) ,we induced a tilt of the molecules with respect to the bilayer normal and produced electric current perpendicular to the tilt plane, with the chiral lipids only. Because most of the living cell membranes contain chiral lipids, we hypothesize that piezoelectricity may have a role in the function of cell membranes. For example, this coupling allows for a wide variety of sensory possibilities of cell membranes such as mechano-reception, magneto-sensitivity, and proton membrane transport. Preliminary results on electromechanical couplings in Saccharomyces cerevisiae (Baker's yeast) and their protoplasts will be also reported and discussed.Endnotesi A. Jakli, J. Harden, C. Notz and C. Bailey, Liquid Crystals, 35 (4), 395-400 (2008).

Depolarization of light in microstructured fibers filled with liquid crystals

AbstractIn the paper we analyze microstructured optical fibers filled with typical nematic liquid crystals, i.e., 5CB and 6CHBT under influence of external electric field or temperature. We use the modified Mueller matrix method with an additional depolarization matrix to calculate degree of polarization changes of the light propagating in the liquid-crystal infiltrated microstructured optical fibers. Preliminary experimental results of light depolarization measurements during propagation in these microstructured fibers are also presented.

Effect of polarization and coherence of low-intensity optical radiation on fish embryos

We have shown that brief exposure of sturgeon embryos (fertilized roe) in the organogenesis stage to low-intensity radiation in the visible region of the spectrum can have a long-term effect on embryonic and post-embryonic development of the fish, detectable 50 days after the irradiation procedure. The biological effects (size-weight characteristics and hardiness parameters of the fish relative to unfavorable habitat conditions) induced by linearly polarized emission from a monochromatic laser source (helium-neon laser, λ = 632.8 nm, Δλ ≈ 0.02 nm) and a quasi-monochromatic light-emitting diode (LED) source (maximum in emission spectrum λ = 631 nm, Δ λ = 15 nm) are practically the same. Going to broadband linearly polarized radiation (λ = 420–800 nm) is accompanied by a decrease in the biological effect. From the results of studies of the effect on embryos from linearly polarized and unpolarized radiation from an LED source and also the effect of linearly polarized, circularly polarized, and unpolarized radiation from a helium-neon laser, we concluded that the type of polarization is of critical importance in realization of the biological effect of radiation. In this case, the maximum stimulating effect (on the size×weight characteristics and the hardiness parameters for juvenile fish) is observed on exposure to linearly polarized radiation; the photobiological effect induced in the same dose range by light with natural polarization (i.e., unpolarized) is significantly less pronounced; the stimulating effect of circularly polarized radiation occupies an intermediate position. Based on the presented data and also on data obtained previously, we conclude that among the resonant and nonresonant photophysical processes (orientational effect of light, effect of gradient forces, dipole-dipole interactions, thermooptic processes) capable of inducing photobiological effects dependent on such laser-specific characteristics as polarization and coherence, the determining influence in the processes studied in this work comes from the orientational effect of light and dipole×dipole interactions. And the orientational effect can appear for anisotropic media with liquid-crystal type ordering (especially domains in membranes and multiple-enzyme complexes) both under conditions when there is no resonant absorption and for weakly absorbing structures, and can initiate a change in their conformations and accordingly their functional characteristics.

Dendritic physical gel: A liquid crystalline gel for application in light scattering displays

Dendrimers are fascinating nano-objects which have predictable three-dimensional architecture, monodisperse molecular weight distribution, and various remarkable properties, e.g. encapsulation, catalysis, low viscosity, and unique optical properties. Functionalized dendrimers, i.e. dendrimers incorporating active or reactive functionalities either in the core or at the periphery, are considered new materials with high potential for modern technology applications. The possibility of molecular design of organized supramolecular assemblies constructed from dendritic macromolecules has generated enthusiastic investigations at the frontiers of chemistry, physics, biology, and materials sciences. Along this line, we have reported dipeptide core poly(benzyl ether) dendrimers as a new class of functional dendrimers that form a physical gel in organic solvent with a significantly high gelation ability. Liquid crystals (LCs) play very important roles in modern life, and various types of LC displays have been proposed and put into practical use. A typical LC display has a twist nematic liquid crystal element which is composed of a pair of polarizing plates and a twisted LC layer. The presence of the polarizing plates results in decreased brightness, therefore, recently, several types of display media that do not contain polarizing plates have been proposed. LC gels have great potential for use as an element in the display medium and would not require polarizing plates. In this context, we report the first example of the application of dendritic physical LC gel in light scattering display materials.

Carbon nanotubes in liquid crystals

We review the research on carbon nanotube (CNT) dispersion in liquid crystals (LCs), focusing mainly on the approaches where the aim is to align CNTs along the LC director field, but also covering briefly the proposed possibility to enhance thermotropic LCs by CNT doping. All relevant LC types are considered: thermotropic LC hosts allowing dynamic CNT realignment, lyotropic LC hosts allowing very high concentration of CNTs uniformly aligned over macroscopic areas and consequent removal of the LC, and LC phases formed by CNTs themselves, used in spinning high-quality carbon nanotube fibres. We also discuss the issue of CNT dispersion in some detail, since successful nanotube separation is imperative for success in this field regardless of the type of LC that is considered. We end by defining a few major challenges for the development of the field over the next few years, critical for reaching the stage where industrially viable protocols for LC-based CNT alignment can be defined.

WITHDRAWN: Thermo-electro-optical studies on E7 and E8 nematic type liquid crystals dispersed in PMMA polymer matrix

This article has been withdrawn consistent with Elsevier Policy on Article Withdrawal ( http://www.elsevier.com/locate/withdrawalpolicy ). The Publisher apologizes for any inconvenience this may cause.

Electronic interactions of typical liquid crystal molecules with typical contacted species generated from the surface of different materials

This research tries to explicate the interaction of a typical contacted metal atom or ion with a typical liquid crystal phase, when the liquid crystal is in contact with some surface material. Since high polarizable liquid crystal molecules such as cyano-biphenyls contain considerable π-electrons in the aromatic (biphenyl) core, –C ≡ N groups and lone pairs on different atoms such as halogens, they can attract neutral or ionic metal particles from the substrate or the coated surface. It has been shown by ab-initio calculations that a typical liquid crystal molecule can make strong back bonding or strong electrostatic bonding to transition metals such as Ni or to metal ions such as Na +, respectively. The interaction of transition metals with aliphatic triple (or double) bonds in the liquid crystal via back bonding causes the deviation of molecular linearity, which may alter the properties of the liquid crystal. The results show that the liquid crystal is also able to form specific interaction such as hydrogen bonding with a hydrophilic polymer such as polyvinyl alcohol (PVA). The dipole moment, the moment of inertia and the polarizability will usually increase altering the alignment properties of the liquid crystal.