4-烷基-4′-氰基联苯的提纯

4-烷基-4’-氰基联苯液晶为显示用混合液晶的主要成分,这类液晶的大多数在室温时呈乳白色液晶相;且具有优良的电气、电光性能,化学稳定性好及液晶相温度范围适中等优点。本文叙述了这类液晶在真空蒸馏基础上进一步采用低温重结晶进行提纯的方法,从而提高了产品质量,使各项指标均符合液晶显示器的要求。     

液晶及其在气相色谱中的应用

液晶是一类有机化合物,在液晶相它既具有液体又具有晶体的特性。其颜色或透明度可随外界条件(如温度、电场、磁场、吸附气体等)变化而变化。近年来,这类材料开始应用于显示、电视、无损探伤、检查癌症和核磁共振研究等方面。液晶又可作为气相色谱的固定液以分离芳香族异构体等。因此,液晶及其应用的研究在国防、医学、化工、电子工业上引起国内外广泛的重视。     

界面致稳型柔性胆甾相液晶显示器件的制备与性能

以镀有氧化锡铟的聚对苯二甲酸乙二酯（ITO-PET）薄膜为柔性电极,对电极导电表面进行处理,以间隔子控制器件厚度,采用灌注法制备了界面致稳型可挠性双稳态胆甾相液晶显示器件。利用接触角测试仪、显微镜和紫外-可见分光光度等分析胆甾相液晶显示器件的微观结构及光电特性。结果表明,表面处理涂层可与液晶分子作用并产生界面致稳效应;采用大小为6 μm的间隔子,当改性层溶液中间隔子质量分数为3%时,制备了有效面积为10×15 cm²的柔性双稳态液晶显示器件,测得饱和驱动电压为40 V,在550 nm的透过率为90%;最后通过刻蚀技术处理器件电极制备了字符显示器件。     

铁电液晶的分子结构和性能

响应速度快和双稳态是铁电液晶最大的优点，本文综述了各类铁电液晶的分子结构与其化学、物理性能之间的关系，为合成宽温程、高自发极化强度，负介电各向异性，长螺矩和低旋转粘度的室温铁电液晶作了理论准备。     

胆甾烯基油酰基碳酸酯的合成

<正> 一、前言液晶自1888年由奥地利植物学家莱尼择尔(F.Reinitzer)发现以来,至今已经一百周年,但它的应用却是近二十多年才由世界各国迅速发展起来的。除了向列相液晶被广泛应用于数字显示,图象显示及气相色谱固定液外,近几年来胆甾相液晶的应用也有了较大发展。利用胆甾相液晶的温度效应,可制作液晶温度计,以进行温度显示;制成各种液晶热敏元件,如液晶商标等,并在医学上用     

新型液晶光阀特性研究

<正> 一、原理外加电场可以改变液晶膜的透光性能,此特性称为液晶的电光效应。目前普遍用于显示技术上的液晶电光效应有扭曲效应、动态散射效应等。此类效应由于对外电场的响应速度过慢(如扭曲效应),或由于对比度不佳(如动态散射效应),因此在许多情况下往往不能满足显示技术的要求。为此,我们利用了“电场诱导下的胆甾-向列相液晶的相转变效应”,制成快速、高对比度的液晶光阀,它能满意地达到快速、高对比度、低功耗的显示技术的要求。如众所知,向列相液晶分子具有平行排列的趋向,我们常用方向矢n_0表示这种取向(图1-a)。而在胆甾相液晶中,分子呈螺旋状分布(图1-b),其螺距p_0在     

纤维素衍生物/二氯乙酸液晶溶液的织态结构[摘]

纤维素衍生物,如乙基纤维素,甲基纤维素,乙基氰乙基纤维素,乙基醋酸纤维素等与二氯乙酸所形成的溶液在浓度达到临界值以上后,出现胆甾型液晶相。在这类溶液中,液晶相的织态结构具有多重性,即胆甾型液晶相的织构随溶液浓度和温度而变化。在不同的浓度范围内,溶致性液晶可呈现出圆盘织构,条纹织构,假各向同性织构和具有鲜艳色彩的平面织构。这些织构均具有胆甾型液晶的特征。在液晶相刚形成,溶液处于     

含乙烯基末端的液晶二聚体的合成与液晶行为研究

合成了一种新型的末端含不饱和双键的席夫碱类液晶化合物,分子结构中含有刚性酯类液晶基元及亚胺间隔基结构,并通过扫描量热(DSC)和偏光显微镜(POM)对其介晶相转变行为进行了表征。结果表明该二聚体与单体表现出不同的液晶行为,二聚体不仅具有向列相(N)液晶结构(120~139℃),且在低温区间显示出层状的近晶C型(SmC)液晶结构(91~120℃),液晶稳定性明显高于单体(单体液晶相温度范围为45~64℃)。实验结果为合成稳定的液晶化合物提供了实验依据。     

含氟盘状液晶研究进展

近年来，在分子中引入氟原子进行改性成为材料研究的热点之一。分子中引入氟原子后，可以影响其热性能、电荷输运性能以及液晶的相行为等，最终改善材料的热、光、电和磁等性质。含氟盘状液晶由于具有较高的载流子迁移率，其合成方法和性质得到了广泛的关注。在含氟盘状液晶分子的平面核上、外围侧链或桥体上取代的氟原子均能显著改变液晶的相变性质，如提升液晶相的热稳定性和柱状相的有序度等。该文综述了近十年来具有代表性的利用氟原子改性盘状液晶的研究进展，进一步证实了氟化有利于改善液晶性质，并进一步归纳了含氟盘状分子在其他领域的应用。盘状液晶氟化后所表现出的优异性能，有助于启发科研工作者在药物合成、无机材料等领域引入含氟材料。     

基于光控二芳基乙烯的手性向列相液晶体系研究进展

光控手性分子开关结合到液晶材料体系中,可以有效利用其光诱导的手性变化,实现远程光刺激液晶材料的自组装螺旋超结构。二芳基乙烯（DAE）是一类新型的、有前景的光致变色分子,作为智能光响应开关,在手性向列相液晶材料体系中表现出优异的性能。本文重点围绕结构设计,总结了一系列具备不同螺旋扭曲力（HTP）的手性DAE分子及其在液晶自组装螺旋结构中所产生的特定性能,如光可逆宽范围调控和光控手性反转。该类光控DAE手性向列相液晶体系在手性调控、光学显示、可调谐激光等领域具有巨大的应用潜力。最后讨论了该领域面临的挑战和机遇,并指出了未来可能的发展方向。     

Nematic–isotropic transition in polymer‐confined and polymer‐free liquid crystal mixtures

Depending on the processing conditions in liquid crystal (LC) display manufacturing, LC/polymer composite films may exhibit unusual properties with respect to the compositional and phase behavior of the LC constituents. In particular, we have observed extraordinary large shifts of phase transition temperatures in LC/polymer composites, which can not be explained by preferential solvation or adsorption. Therefore, the influence of real manufacturing conditions such as thermal stress, storage in vacuum, and UV irradiation on the nematic–isotropic (n–i) transition temperatures of commercial nematic mixtures was investigated. Shifts of the clearing temperature of up to 88 K, presumably due to partial evaporation or UV degradation, were observed. Furthermore, we found that annealing may lead to the replacement of the nematic phase by the smectic A phase at room temperature in both LC/polymer composites and pure LC samples. Among the tested commercial LC blends, the mixtures E7, MLC‐6650, and L101 showed the smallest stress effects. Practical consequences of our results are discussed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Display forming polymer/liquid crystal composite layers and their stability against external mechanical distortions

The liquid crystal display (LCD) technology is confronted with the task to substitute rigid glass plates enclosing the electro‐optically active liquid crystal (LC) material by plastic substrates. In particular, the commercialization of flexible displays requires a sufficient stabilization against external mechanical distortions. To achieve LC layer stabilization, several procedures have been suggested. In this work, the thermal‐induced phase separation (TIPS) technique has been applied to generate composite films consisting of LC compartments which are encased by coherent polymer walls after binodal phase separation. Composite films were prepared from a series of poly(methacrylates) and various commercial nematic LC mixtures. Furthermore, the use of copolymers as well as binary blends from “hard” and “soft” poly(methacrylates) broadens the possibilities to control the film morphology. To compare different polymer/LC composite films regarding their stability under compression load, the samples were investigated by indentation tests using an inverse reflected‐light microscope combined with a digital image acquisition technique. The deformation of the composite layers was evaluated by the uniDAC image analysis which relies on the more general method of Digital Image Correlation (DIC). Some of the fabricated composites show a remarkably high indentation resistance, especially such prepared from poly(1‐tetralyl methacrylate) and poly(4‐tert‐butylcyclohexyl methacrylate). The results facilitate the selection of suitable composite systems for the fabrication of mechanically stabilized flexible LC displays. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Morphological studies of LC polymer networks prepared by photopolymerization of (LC monomer/LC) blends

The morphology of LC polymer networks prepared by photopolymerization of (LC monomer/LC) blends containing photoinitiator and crosslinker was investigated. For the blends of 4-acryloyloxyhexyloxy-4′-cyanobiphenyl and 4-hexyloxy-4′-cyanobiphenyl, which had the same mesogen, orientation order of LC textures was memorized by photopolymerization, while any structure of LC polymer networks was not observed under an optical microscope because the networks did not phase separate from the low molecular weight LC. However, specific anisotropic phase-separated structures of LC polymer networks were observed for the blends of 4-acryloxloxyhexyloxy-4′-cyanobiphenyl and 4-hexyloxybenzoic acid, which had dissimilar mesogens, on condition that photopolymerization was carried out under the LC phase. If photopolymerization was performed under the isotropic phase conditions, polygonal or continuous phase-separated structures of LC polymer networks were observed for the dissimilar mesogenic blend. These morphologies were strongly dependent on the phase diagrams of (LC monomer/LC) blends and (the corresponding LC polymer/LC) blends. It has been found that the ordering field of LC molecules can give LC polymer networks anisotropic morphologies, which have the long range as the same length scale of LC textures.     

Morphology of a hydrogen-bonded LC polymer prepared by photopolymerization-induced phase separation under an isotropic phase

A hydrogen-bonded LC polymer was prepared by photopolymerization of an LC blend composed of 4-(6-acryloyloxyhexyloxy)benzoic acid (A6OBA) and 4-hexyloxy-4′-cyanobiphenyl (6OCB), containing small amounts of an inhibitor and photoinitiator, at two different temperatures in an isotropic phase. To elucidate the factors determining the morphology of the obtained polymer (poly(A6OBA)), we chose two irradiation temperatures: one in the LC temperature range of the polymer, the other in the isotropic range. We investigated structures of the polymers by optical microscopy and scanning electron microscopy. SEM images showed that the film obtained at the lower temperature consisted of randomly extended fibers having a diameter of ca. 1.0 μm and some branches, whereas the film prepared at the higher temperature was composed of polymer particles with a diameter ca. 1.5 μm. By comparing these results with those of an earlier experiment in which we obtained macroscopically oriented LC fibers by photopolymerization under the LC phase of the blend, we infer the following; (i) the presence of an LC phase in the resulting polymer itself during photopolymerization is necessary for it to form fibrous morphology and (ii) the LC ordering field present prior to photopolymerization is not indispensable for the fibrous morphology but it is for the macroscopic orientation and reduction of the branches in the fibers.     

Morphological self-control of a phase-separated polymer during photopolymerization in a liquid-crystalline medium

An acrylate monomer having a cyanobiphenyl mesogen (1) was photopolymerized in a liquid-crystalline (LC) ordering field of 4-hexyloxybenzoic acid (2). A blend of (1) and (2) (molar ratio: 1:4), containing a photoinitiator, an inhibitor and a crosslinker, was irradiated with UV light at 120 and 137 °C in order to investigate the effect of an LC phase on the resulting polymer. Here, both temperatures are in the nematic temperature range of the blend, however, the former is in the LC temperature range of the polymer, whereas the latter is in the isotropic temperature range. Scanning electron microscopy of the obtained polymers revealed that the polymer prepared at 120 °C consisted of oriented fine fibers, measuring ca. 400 nm in diameter, while that obtained at 137 °C had a fused bead-like morphology. In addition, we investigated the effect of crosslinking on the morphology by comparing the results from the blends with and without a crosslinker. We found that the LC phase of the phase-separated polymer is one of the necessary conditions for the formation of the fine fiber structures.     

Synthesis and Electroluminescence of Side-chain Liquid Crystalline Polyacrylates and Polyoxiranes Containing Bistolane Side Groups

The synthesis and characterization of side-chain liquid crystalline (LC) polyacrylates and polyoxiranes containing bistolane side-groups are presented. The phase behavior of the prepared monomers and polymers was characterized by differential scanning calorimetry and optical polarizing microscopy. All of the obtained monomers and polymers reveal an enantiotropic nematic phase. The birefringences of the LC monomers are in the range from 0.35–0.6 depending on the measuring wavelength. The photoluminescence (PL) and electroluminescence (EL) properties of the obtained monomers and polymers are also reported.     

Preparation of composites of polymer liquid crystal/cholesteric liquid crystal and their photochemical switching and memory properties by photoisomerization of a chiral azobenzene molecule

A chiral azobenzene compound was synthesized, and mixing the chiral azobenzene compound in a host nematic liquid crystal (LC) induced a cholesteric phase. The twisting power of the trans‐form of the chiral azobenzene compound was larger than that of its cis‐form produced by ultraviolet irradiation. A low molecular weight compensated nematic LC was then prepared by mixing of the chiral azobenzene and a nonphotochromic chiral compound, thus giving mutual opposite helical sense in the host LC. Reversible optical switching between transparent and opaque was achieved by ultraviolet and visible light irradiation. However, the photochemically switched opaque state was not stable even in the dark. Stability of the opaque state was found to be improved by adding polymer LC to the low molecular weight compensated nematic LC. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2577–2580, 2004     

Analytical Methods for Determination of Polycyclic Aromatic Hydrocarbons (PAHs) — A Historical Perspective on the 16 U.S. EPA Priority Pollutant PAHs

The identification of 16 polycyclic aromatic hydrocarbons (PAHs) as priority pollutants by the U.S. Environmental Protection Agency (EPA) in 1976 has been a primary driver for analytical methods development for the determination of PAHs. In this article, the historical development of methods in liquid chromatography (LC) and gas chromatography (GC) to separate these 16 PAHs is discussed. In LC a significant effort was the search for and the fundamental understanding of the unique stationary phase capable of achieving the desired separation of the 16 EPA PAHs. For GC methods, the focus on stationary phase development has been the separation of critical isomers with a broader scope than the 16 EPA PAHs. The current routine LC and GC methods for the 16 EPA PAHs are well established; however, new advances in analytical techniques beyond LC and GC are discussed. Many analysts are now interested in more than just the 16 EPA PAHs (e.g., higher molecular mass PAHs and alkyl-substituted PAHs) and analytical methods have emerged to address these needs. Reference materials and their use in the determination of PAHs are discussed.     

70%嘧菌·霜脲氰水分散粒剂液相色谱定量分析

建立了在同一色谱条件下测定混剂中嘧菌酯和霜脲氰含量的方法。采用200 mm×4.60 mm(i.d.)SinoChrom ODS-BP柱分离,以乙腈-水(体积比为60:40)为流动相,在225 nm紫外检测波长下,经保留时间定性确证,峰面积外标法进行定量分析。嘧菌酯与霜脲氰的线性相关系数分别为1.000 0和1.0000;变异系数分别为0.39%和O.22%;平均回收率分别为99.78%和99.68%。该方法操作简便快捷,准确度和精密度高,线性相关性好。     

Antibody phage display libraries: contributions to oncology

Since the advent of phage display technology, dating back to 1985, antibody libraries displayed on filamentous phage surfaces have been used to identify specific binders for many different purposes, including the recognition of tumors. Phage display represents a high-throughput technique for screening billions of random fusion antibodies against virtually any target on the surface or inside cancer cells, or even soluble markers found in patient serum. Many phage display derived binders targeting important tumor markers have been identified. Selection directed to tumoral cells' surfaces lead to the identification of unknown tumoral markers. Also the improvement of methods that require smaller amounts of cells has opened the possibility to use this approach on patient samples. Robust techniques combining an antibody library displayed on the phage surface and protein microarray allowed the identification of auto antibodies recognized by patient sera. Many Ab molecules directly or indirectly targeting angiogenesis have been identified, and one of them, ramucirumab, has been tested in 27 phase I-III clinical trials in a broad array of cancers. Examples of such antibodies will be discussed here with emphasis on those used as probes for molecular imaging and other clinical trials.