Synthesis and Liquid Crystal Behavior of a Novel Ester Homologous Series

A novel ester homologous series of 4-[4’-n-alkoxy cinnamoyloxy] benzyl benzoates has been synthesized. The series consists of 12 homologues. Liquid crystal properties commence from the sixth member to the last member of the series with the exhibition of an enantiotropic nematic phase without the exhibition of any smectogenic mesophase. The remaining homologues do not exhibit liquid crystal behavior. The texture of the nematic phase is of the threaded or Schlieren type. The solid-nematic or isotropic transition curve adopts a zigzag path and the nematic-isotropic transition curve steeply rises and then falls in the phase diagram and behaves in normal manner. An odd–even effect is absent in the nematic-isotropic transition curve with an alteration of transition temperatures. The average thermal stability for the nematic mesophase is 153.1°C, and the nematogenic temperature ranges vary from 12°C to 50°C. Analytical data confirm the molecular structures of the homologues. The Liquid Crystal properties and transition temperatures were observed through an optical polarizing microscope, equipped with a heating stage. The mesomorphic characteristics of the novel ester series are compared with other, known and structurally similar series. The novel series is predominantly nematogenic with the absence of any smectogenic character, with relatively short mesophase temperature ranges and of the middle ordered melting type.     

Photo Alignment and Patterning of Liquid Crystal Polymer Films and Optical Devices by Side-Chain Photopolymers

Prerequisite for virtually all nematic field-effects on which liquid crystal displays (LCDs) are based is stable, uniaxial surface alignment with defined bias tilt angle between the long liquid crystal (LC) axes and their display boundaries. Since the invention of the TN-LCD [1 Schadt, M., & Helfrich, W. (1972). Mol. Cryst. Liq. Cryst., 17, 355.[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]] in 1970 until recently this was achieved by confining liquid crystals between mechanically brushed surfaces [2 Cognard, J. (1982). J. Mol. Cryst. Liq. Cryst. Suppl. Ser., 1, 1–74. [Google Scholar]–4 Aoyama, H., Yamazaki, Y., Matsuura, N., Mada, H., & Kobayashi, S. (1981). Mol. Cryst. Liq. Cryst. Lett., 72, 127.[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]]. We have first shown in the 1990s that, non-mechanical, uniaxial, tilted and patterned LC-alignment is possible by anisotropic Van der Waals surface interactions [5 Schadt, M., Seiberle, H., & Schuster, A. (1996). Nature, 381, 212. US Patent (1995) US-6, 215, 539.[Crossref], [Web of Science ®] , [Google Scholar]], namely by directional polymerization of photo-sensitive side-chain polymers films [5 Schadt, M., Seiberle, H., & Schuster, A. (1996). Nature, 381, 212. US Patent (1995) US-6, 215, 539.[Crossref], [Web of Science ®] , [Google Scholar], 6 Schadt, M., Schmitt, K., Kozinkov, V. & Chigrinov, V.G. (1992). Jpn. J. Appl. Phys., 31, 2155. US patent (1991) US 5,389,698.[Crossref], [Web of Science ®] , [Google Scholar]] by linear polarized UV light. The LPP model is reviewed and its applications enabling high resolution multi-domain liquid crystal displays operated in transmission and reflection are discussed. Examples are given for optical retarders integrated into LCDs, anisotropic liquid crystal polymer (LCP)-films for 3D imaging, interference color filters, wide-view films and anisotropic polymer surface topologies.     

Influence of a.c. Electric Field on Infrared Absorption Spectra of Liquid Crystals and Determination of Orientational Order Parameter by Infrared Dichroism. II. Molecules with Weak Negative Dielectric Anisotropy

The influence of a.c. electric field (10 kHz) on the IR spectra of the nematic phase of six p-alkoxybenzylidene-p,n-butylanilines with weak negative dielectric anisotropy was studied and the temperature dependence of the orientational order parameter and threshold voltage have been investigated. The values of band elastic constants K₃₃ were calculated for MBBA and EBBA.     

Mesomorphism dependence on molecular rigidity and substitution of same functional group on lateral or terminal position of tailed phenyl ring

Novel liquid crystal materials (LCs) of low temperature range (53°C to 75°C) have been synthesized through a series of chalconyl derivatives consisting of two phenyl rings bonded through a –CH?CH?CO? central bridge to study the effect of molecular structure on LC properties in general and with a focus on molecular rigidity. The novel homologues series (C₁ to C₁₈) consists of thirteen homologues with general formula RO?C₆H₄?CH?CH?CO?C₆H₄?OC₁₀H₂₁(n) (meta). The C₁, C₂, C₃ homologues are nonliquid crystals (NLC) and the rest of the homologues (C₄ to C₁₈) are either monotropic or enantiotropic liquid crystals. C₄ to C₆ homologues are enantiotropicnematic and the rest of the mesomorphic homologues are (C₇ to C₁₈) monotropicsmectic in addition to monotropicnematic character. Transition and melting temperatures including textures of homologues were determined by an optical polarizing (POM) microscopy equipped with a heating stage. Textures of a nematic phase are threaded or Schlieren, and that of the smectic phase are of the type Smectic A or C as judged directly from the heating top of the microscope. Thermal stability for smectic is very poor and of the nematic is (N-I) 69.3°C whose, total mesophase length ranges between 07.0 to 14.0°C at C₈ and C₄ homologues respectively.     

Color Gamut of Liquid Crystal Polysiloxanest

Polysiloxanes with suitable side-chains form a cholesteric liquid crystal phase that can be applied to a substrate to produce a durable coating which exhibits strong colours below the glass transition temperature. The peak reflectance is almost 0.5 and a nearly 1.0 peak reflectance can be obtained using a half-wave retardation plate coated on both sides with the material and viewed from one direction against a black background. Values below 0.5 and between 0.5 and 1.0 have been also obtained using suitable solvents and alignment techniques. Many desired spectral reflectance distributions can be then obtained because of the additive color properties of such cholesteric coatings. As a result it is possible to produce a larger colour gamut than with real surface colours such as pigments and dyes. Employing commercially available material experimental work was carried out demonstrating a greatly expanded colour gamut on the chro-maticity diagram. Also it is possible to modify the spectral reflectance distribution of coloured substrates by coating them with a material having a reflectance peak at the desired band of wavelength.     

Study of a new homologous series of liquid crystals: Isopropyl-p-(p/-n-alkoxy cinnamoyloxy) cinnamates

A new homologous series: isopropyl-p-[p^/-n-alkoxy cinnamoyloxy] cinnamates was synthesized and studied with a view to understanding and establishing the relation between liquid crystal property and molecular structure. Twelve homologues were synthesized. Methyl to butyl homologues are not liquid crystals, while pentyl, hexyl, heptyl, octyl, decyl, dodecyl, tetradecyl, and hexadecyl derivatives are enantiotropic liquid crystal in nature with nematogenic character. Smectogenic character is totally absent. A phase diagram is obtained by plotting a graph of transition temperatures versus number of carbon atoms is n-alkyl chain of left n-alkoxy terminal end group. Solid-isotropic or solid-nematic transition curve rises steeply from methyl to propyl derivatives and falls to pentyl homologue through butyl homologue, and follows a zigzag path of rising and falling values as the series is ascended. Nematic–isotropic transition curve shows descending tendency as series is ascended in a normal manner with exhibition of odd-even effect. Smectic mesophase does not appear even in the monotropic condition. Phase transition temperatures are determined by hot stage polarizing microscope. Analytical data support the structure of molecules. Texture of nematic mesophase is of threaded type. Mesomorphic properties are compared with structurally similar homologous series.     

Nonlocal Continuum Theory of Liquid Crystals

A nonlocal continuum theory of liquid crystals is constructed to explain and predict the physical behavior of liquid crystals under long range intermolecular forces Balance laws consist of conservation of mass and mocroinertia, balance of momenta and energy. Constitutive equations are given for the equibilibirium and non-equilibirium parts of the stress, couple strees, free energy, entropy an nonlocal body force and couple. Thermodynamic restrinctions and material frame-indifference are studied. The theory is valid for liquid crystals having arbitrary shapes (inertia), Passage is made to the thread-like molecuels and to local theory. Applications are considered to two-dimensional problmes, steady, plane shear flows and disperison of twist waves.     

Mesomorphism Dependence of Molecular Flexibility with Reference to Bromo Tail Group

Halogenated chalconyl derivatives of novel homologues of esters are synthesized and studied with a view to evaluate their liquid crystal (LC) properties and their dependence on molecular structure with reference to molecular rigidity and flexibility. Novel homologous series of chalconyl esters comprises 12 homologues. All the members of a series are enantiotropically smectogenic. Nematogenic mesophase is missing throughout the series. Textures of smectic phase are of type A or C, as judged either by observing directly the sample homologue through polarizing microscopy or some selected members of the series by miscibility method. Transition temperatures were observed through an optical polarizing microscope equipped with a heating stage. The Cr-Sm transition curve adopts zigzag path and behaves in a normal manner. Sm-I transition curve exhibits an odd-even effect and behaves in a usual established manner. The average thermal stability for smectic is 154.79°C, and the mesogenic phase length range is from 5.1 to 24.4°C. The LC properties of the novel series are compared with structurally similar other known series. Thus, present novel series is fully smectogenic with middle ordered melting type and short range of liquid crystallinity.     

Diamagnetic Anisotropy Measurements of Nematic Liquid Crystals

Electro-optic effect of liquid crystals in the presence of a magnetic field was investigated. Two independent techniques: magnetic field dependent threshold voltage and magnetic field-assisted relaxation time, were used to evaluate the diamagnetic anisotropy for three nematic liquid crystals: BDH-E7, RO-TN-103 and ZLI-1132. Correlation between the diamagnetic anisotropy and the molecular structures was obtained. This information is particularly important for synthesizing liquid crystal components with desired diamagnetic anisotropy.     

Application of Infrared ATR Spectroscopy to Liquid Crystals. III

Infrared absorption measurements of nematic N-(p-ethoxybenzylidene)-p'-cyanoaniline (EBCA) under a DC electric field were performed by means of our previously reported ATR method. DC voltages up to 15V were applied to the nematic liquid crystal 15 μm thick between a silicon ATR prism (probing electrode) and an In₂O₃-coated glass electrode (opposite electrode). By using this method the orientational behavior of molecules in boundary layers about 1 μm thick at the Si electrode was investigated.

The threshold voltage for the dielectric orientation varied from 2 to 6 V depending upon the boundary conditions at the opposite electrode, and the maximum degree of order of homeotropic orientation was found to be 0.6–0.7. A storage effect, in which a homeotropic texture induced by the electric field remains unaltered even if the field is removed or reversed, was observed.     

Dielectric Spectroscopy of Side Chain Siloxane Liquid Crystal Copolymers

Side chain siloxane liquid crystal polymers (LCPs) are being investigated as potential optical storage media. Dielectric relaxation spectroscopy has been used to examine the real and imaginary components of permittivity as a function of frequency and temperature. The spectra obtained are discussed from the standpoint of both their molecular significance and their device implications. Spectra of liquid crystal homopolymers and a particular class of copolymers have been found to exhibit different features due to the larger free volume available to the mesogenic moieties in the copolymers. The relaxation behaviour of five LC copolymers is discussed and then two equivalent pairs of homopolymer and copolymer LCPs are considered in more detail. One pair shows anomalous relaxation behaviour and extra relaxation processes are attributed to internal reorientations.     

微波法快速制备碱式硫酸镁晶须

以七水硫酸镁为原料、氢氧化钠为沉淀剂,采用微波法制备出纤维状的碱式硫酸镁晶须.考察了反应温度、反应时间、物料摩尔比、硫酸镁浓度及晶种添加量等因素对晶须形貌的影响.研究结果表明:在硫酸镁浓度1.6 mol/L、硫酸镁和氢氧化钠摩尔比1∶1、晶种添加量(质量分数)1;、微波反应温度160～ 180℃、反应时间30～ 60 min的条件下,可以制备出纤维状的152型碱式硫酸镁晶须.以微波法制备碱式硫酸镁晶须大大缩短了反应时间.     

Vibrational Spectra of Liquid Crystals. XII

Abstract

Recent papers by Gray et al.¹ have discussed the synthesis, structure, and properties of the mesomorphic 4-cyano, 4′-alkyl (or alkoxy) biphenyls. The reports on these materials have made mention of the existence of solid state dimorphism for certain homologs. This paper discusses this dimorphism as it manifests itself in the Raman spectrum of the octyloxy homolog (hereinafter referred to as 80CB) in the CN stretching region.

The approach used involves direct measurement of the Raman spectrum as a function of temperature, as well as computation of a correlation function obtained from the Raman band envelope by means of Fourier transformation. The application of this correlation function technique to this system has been discussed by us recently in detail.^2,3

Gray and Mosley,⁴ in a recent study of the Raman spectrum of 4-cyano, 4′-pentylbiphenyl note that the CN stretch of this compound is a doublet in the solid phase (2224 and 2233 cm^?1), but only the 2224 cm^?1 band appears in the nematic phase. They further report that only a single band appears in the CN stretching spectrum of solid 4'-heptyl-, -hexyl-, and -butyl-derivative. They speculate that the doublet might appear in the spectrum of the metastable solid phase of the heptyl homolog.

In this work, we show that for 80CB this is not the case. Rather, a doublet is observed for the stable solid but not for the metastable. The origin of this doublet is discussed, and all of the CN stretches for stable solid, metastable solid, and smectic liquid crystal are analyzed from the viewpoint of the vibrational relaxation correlation function.     

微波法热处理制备CaO-MgO-Al2O3-SiO2系微晶玻璃的研究

以二氧化硅,三氧化二铝,氧化钙和氧化镁为主要原料,分别采用微波辐射和传统电加热制备了一系列CaO-MgO-Al2O3-SiO2 (CMAS)系微晶玻璃材料,对比两种方法的热处理制度对微晶玻璃结构与性能的影响,并进一步讨论了微波非热效应的影响.利用DTA、XRD、SEM和综合力学性能仪等手段,研究了两种对该系微晶玻璃显微结构及性能的影响.实验结果表明,两种方法制备的微晶玻璃主晶相均为辉石相,力学性能也基本相当.与传统热处理方法相比,微波法可在更短时间内制备出性能较好的微晶玻璃材料,微波非热效应有助于降低其晶化温度.     

A Theoretical Study of Molecular Ordering of Some Smectic Liquid Crystals

Abstract

A theoretical investigation of molecular ordering of smectic C liquuid crystals C₈H₁₇O-C₆H₄-C₆H ₄-COO-C₆H₄-OC₈H₁₇ { A }, C₉H₁₉O-C₆H₄-COO- C₆H₄-COO-C₆H₄-NO₂ { B } and its binary mixtures { A+B } has been carried out by the method based on the Rayleigth-Schrodinger perturbation theory. The mutual arrangement of two molecules corresponding to the minimum of the total interaction energy between them U_pair has been established. The curves of the dependence of U_pair and its various contributions on displacement of molecules from each other along the molecular long X-axis and angle θ between molecules' long axes has been also computed in the minimum point vicinity. The obtained results make it possible to determine the peculiarities of the structural organization of molecules, as well as to construct a model of the structure of A and B compounds in different phases taking into account the most probable packing of molecules.     

微波诱导制备纳米氧化锆及其机理研究

以ZrOCl2·8H2O和CO(NH2)2为原料,利用微波诱导均匀沉淀法制得了纳米ZrO2,考察了微波加热与常规加热的不同之处以及微波加热对粒径大小、均匀度、晶化温度的影响,采用日立H-600型透射电镜、Malvern粒度分布仪、差热分析仪和X射线衍射仪等对产品进行了表征,并得出结论:微波诱导制备纳米氧化锆,所得粒子粒度较小、均匀性好,并对微波加热的原理进行了探讨.     

微波均相沉淀法制备YAG透明陶瓷

以Al(NO3)3和Y(NO3)3为母盐,尿素为沉淀剂,添加适量(NH4)2SO4,采用微波均相沉淀法合成YAG前驱体,经1100℃煅烧得到活性高、分散性好的YAG纳米粉体,添加适量TEOS作烧结助剂,经干压成型,1700℃真空烧结,保温10min得到透明YAG陶瓷.显微观测表明,烧结体气孔含量极低,结构致密,其晶粒形状为规则的多边形,平均尺寸为2.5μm左右.该透明陶瓷在可见光区的最大透光率达到42;,在近红外光区的最大透光率达到74;.     

缓冲层ZnPc对有机电致发光器件特性的影响

本文研究了酞菁锌(ZnPc)薄膜的表面形貌及ZnPc薄膜作为缓冲层对有机电致发光器件(OLEDs)光电特性的影响.对比两组样品的AFM图像,ZnPc薄膜相比于ITO薄膜,其表面的岛面积较大,薄膜表面更连续平整,基本上覆盖了ITO膜表面针孔,减少了表面的缺陷.另外,ZnPc薄膜的岛分布均匀有序.使用ZnPc作为缓冲层的器件性能明显好于未使用ZnPc修饰的器件,在7.42V的驱动电压下的最大发光亮度达到1.428kcd/m2,在4.3V电压驱动下时,最大光功率效率为1.411m/W;而未使用缓冲层的器件在8V的驱动电压下达到最大发光亮度达到1.212kcd/m2,在5.5V电压驱动下时,最大光功率效率为0.931m/W.     

Fabrication of a fast-switching liquid crystal device using reactive self-assembled polyimide alignment layer

ABSTRACT

We proposed a new vertical alignment method for simultaneously improving the alignment force and electro-optical properties. The key point of the new method is the self-assembly of the reactive monomer via hydrogen bonding with the polyimide alignment layer and the formation of pre-tilt using the reactive monomer on an alignment layer. Through the self-assembly of the reactive monomer and the generation of the pre-tilt, it is possible to obtain a higher alignment force and a fast response time. As a result, through a simple additional step, we can fabricate a fast-switching liquid crystal device using a reactive self-assembled alignment layer.