基于多重氢键的超分子液晶研究

基于氢键的超分子液晶体系的研究是一个方兴未艾的充满活力的前沿研究领域,它在化学和生物体系中占据非常重要的位置。本文主要介绍了目前文献报道的基于二重以上氢键的超分子液晶体系的研究进展。     

Chemistry and Applications of Liquid Crystals

Approximately 5% of all organic compounds are transformed at their melting point into liquid crystals—thermodynamically stable, anisotropic liquids which in contrast to isotropic melts appear turbid and are also known as mesophases. Such melts are classed as smectic, nematic, and cholesteric liquid crystalline phases, depending upon the arrangement of the constituent molecules. The discovery of numerous potential applications during the past ten years has awakened the study of liquid crystals from its former slumber as a physical curiosity and placed it in the limelight of the scientific stage. Uses in display systems for measured values and for computer and process data, as well as for remote controlled timetables, for windows of variable light-transmission, etc., appear particularly promising. Not only black-and-white contrasts are now possible but also color production.     

Liquid Crystals: A Tool for Studies on Chirality

Nematic liquid crystals are extremely sensitive to optically active molecules, which, at very low concentration, convert them into cholesteric liquid crystals. The purpose of this report is to review recent applications of liquid crystals to chirality studies. A brief discussion of the structure and properties of liquid crystals is followed by a survey of the methods currently being employed for the determination of the pitch and handedness of cholesteric liquid crystals. Of special interest in the formation of induced-cholestric phases are the twisting powers of optically active compounds and the structural relationships between dopants and nematics. Liquid crystals can be used, inter alia, for the detection of small optical activities and for the determination of thermal racemization barriers and absolute configurations.     

Breaking the Mold of Discotic Liquid Crystals

Small molecules of the indene and pseudoazulene type like 1 and 2 form columnar mesophases! These compounds do not possess peripheral flexible chains like conventional columnar liquid crystals. Instead, polarizable chlorine and sulfur atoms, as well as the polar cyano group, function as unusual soft regions between the rigid columns.     

几类非常规液晶材料的研究进展

本文综述了液晶二聚体、多爪型液晶及香蕉形液晶等几类非常规液晶材料的研究进展。结合笔者近几年的研究积累,着重介绍:(1)液晶二聚体的分子结构与液晶态结构及液晶二聚体所特有的奇偶效应与近晶多形性;(2)多爪型液晶的分子结构与液晶态结构的特点及由于兼有棒状分子与盘状分子的结构特点而具备的特殊的相变性质;(3)香蕉形液晶的分子结构与液晶态结构及香蕉形液晶所特有的手性与极化序。在介绍各类液晶材料的特点及研究热点的同时,围绕分子结构与液晶态结构的关系这一主题,深入讨论了各种液晶材料形成特殊分子排列及表现出特殊物理性质的机理。     

纤维素及其衍生物液晶研究新进展

本文全面地综述了纤维素及其衍生物溶致性液晶和热致性液晶的形成, 液晶性与大分子链结构, 以及具有胆甾型液晶相结构的纤维素衍生物复合材料等方面的最新研究进展。     

液晶光取向技术

光取向技术是一种非接触式液晶取向方法,它具有无污染,不产生静电、易实现分区取向等优点,因而引起广大科技工作者的关注。本文综述了液晶光取向的最新研究进展,包括液晶光取向研究所选用的,各种材料有一定的光照条件下发生的分子结构的变化以及对液 取向方式的影响等。     

液晶CPBOB吸附的STM研究

利用STM对吸附在导电基底上的液晶进行研究，能提供近原子分辨的液晶分子图象，这一创新不仅拓宽了STM的研究领域，也使STM成为研究液晶吸附的重要手段之一．根据液晶相变特征不同，样品的制备方法大致分四种情况：直接法，加热法，气相沉积法和溶剂法．无论采用以上哪种方法，     

A Novel Type of Liquid Crystals Based on Axially Fluorinated Cyclohexane Units

Decidedly higher clearing temperatures and often also broader mesophases are exhibited by axially fluorinated cyclohexane derivatives 1 and 2 relative to their nonfluorinated analogues. A convenient method for the multigram synthesis of 1 and 2 , which represent a promising new type of liquid crystals with positive or negative dielectric anisotropy, is presented.     

单臂冠醚结构与液晶性质

设计并合成了4个单臂冠醚液晶,考察了冠醚环与亲酯性结构单元之间的桥键与液晶性质的关系,中心桥键对单臂冠醚液晶的熔点影响不大,而对液晶热稳定性有较大的影响.     

Thermotropic Liquid Crystals Formed by Intermolecular Hydrogen Bonding Interactions

The role of hydrogen bonding in the formation or stabilization of liquid crystalline phases has only recently been appreciated. Following the first, wellestablished examples of liquid crystal formation from the dimerization of aromatic carboxylic acids, through hydrogen bonding, several classes of compounds have recently been synthesized, the liquid crystalline behavior of which is also dependent on intermolecular hydrogen bonds between similar or dissimilar molecules. In this review the main classes of compounds exhibiting liquid crystallinity due to hydrogen bonding are presented to show the diversity of organic compounds that can be used as building elements in liquid crystals. The molecules are either of the rigid-rod anisotropic or amphiphilic types such as molecules appropriately functionalized with pyridyl and carboxyl groups, whose interaction leads to the formation of liquid crystals; amphiphilic carbohydrates and amphiphilic and bolaamphiphilic compounds with multiple hydroxyl groups whose dimerization or association is indispensable for the formation of liquid crystals; and certain amphiphilic carboxylic acids with monomeric or polymeric mesogens and amphiphilic-type compounds bearing different moieties, whose interaction may lead to the formation of mesomorphic compounds. Associated with the macroscopic display of liquid crystalline phases is the supramolecular structure, and therefore rather extended discussion of these structures are included in this review.     

液晶型化学传感器检测甲基膦酸二甲酯的研究

液晶型化学传感器是利用传感器检测目标化合物前后,液晶分子在敏感膜表面的取向发生变化,改变液晶折射光线的能力,导致传感器的颜色和光亮度发生变化,实现对生物分子、有害化学物质的检测。本实验报道了一种以μm级沟槽状金膜为基底的液晶型化学传感器,通过在具有μm级沟槽(一个沟槽周期5μm)的玻璃基底上进行平面镀金,制备了具有相同沟槽周期的金膜,并在金膜上制备Cu2 修饰的巯基十一酸自组装敏感膜。通过检测甲基膦酸二甲酯时液晶织构的变化,阐明了液晶型化学传感器的作用机理,并证实微米级沟槽状金膜为基底制作的液晶型化学传感器可以用于检测目标化合物。传感器对甲基膦酸二甲酯检测的线性范围0.03~1.00g/m3;线性方程Y=0.14X 0.0035,相关系数r=0.9957。     

A Comparative Analytical Study of Two New Liquid Crystals Used as Stationary Phases in GC

The investigation of the analytical properties of two new nematic sulphur-containing liquid crystals 5-(4-methoxyphenyl)-azophenyl)-2-butylthio-1,3,4-oxadiazole (Phase I) and 5-(4-(propoxyphenyl)-azophenyl)-2-butyl thio-1,3,4-oxadiazole (Phase II) and which comprise units of 1,3,4-oxadiazole instead of the aromatic cycles, was carried out by gas chromatography using glass capillary columns. For this purpose, many solutes belonging to various families and having different polarities and volatilities were injected. Comparison of the retention data of the studied components has shown that Phase II allowed a better separation than the other phase. The two liquid crystalline materials show a good separation of the studied isomers except for xylene.     

Aromatic Heterocycles Used as Terminal Groups of Calamitic Liquid Crystals

Three series of compounds 1 ‐ 21 were prepared by using 2‐, 3‐, and 4‐pyridinemethanol as terminal group of calamitic liquid crystals. These compounds have some similarities in their phase behavior. They all exhibit SmA phase. A tilt smectic phase, SmC, will be formed when their flexible alkoxy chain is longer than hexoxy group. The profound difference between them is that the compounds 15 ‐ 17 possess a short temperature range of N phase. The compounds 3 and 6 have the widest SmA phase, up to 94 °C, and SmC phase, up to 46 °C, respectively.     

Enantiopure Trioxadecalin Derived Liquid Crystals: Influence of the Nature of the Phenyl Substituent on the Mesogenic Properties

Reaction of pseudo‐glucal 1 with Grignard reagents derived from 1‐bromo‐4‐(trimethylsilyloxy)benzene, 1‐bromo‐4‐methoxybenzene, 1‐bromo‐4‐methoxymethoxybenzene, 1‐bromo‐4‐dimethylaminobenzene, in the presence of a catalytic amount of NiCl₂(dppe), gives the corresponding unsaturated β‐C‐aryl glycosides 2. Desilylation and hydrogenation of 2 leads to β‐C‐aryl glycosides 4, which can be used as chiral precursor compounds in the synthesis of chiral liquid crystals. Combination of 4 with arylaldehydes leads to compounds 5–7, whereas reaction with p‐alkoxysubstituted phenylboronic acids gives the trioxaboradecalins 8–11. The mesogenic properties of these compounds are strongly influenced by the nature of the substituent on the phenyl ring in the molecule.     

P,N配位的环钯配合物催化Suzuki偶联合成含氟液晶化合物的研究

合成了P,N配位的环钯配合物1-2.它们不仅是在室温下高效催化对溴甲苯与对氟苯硼酸的交叉偶联反应而且也是合成含氟液晶化合物的高效催化剂.在最佳反应条件下,含氟液晶化合物的产率都超过90%.     

Fluctuating Interfaces in Liquid Crystals

Summary: We review and compare recent work on the properties of fluctuating interfaces between isotropic and nematic liquid-crystalline phases. Molecular dynamics and Monte Carlo simulations have been carried out for systems of ellipsoids and hard rods with aspect ratio 15:1, and the fluctuation spectrum of interface positions (the capillary wave spectrum) has been analyzed. In addition, the capillary wave spectrum has been calculated analytically within the Landau-de Gennes theory. The theory predicts that the interfacial fluctuations can be described in terms of a wave vector dependent interfacial tension, which is anisotropic at small wavelengths (stiff director regime) and becomes isotropic at large wavelengths (flexible director regime). After determining the elastic constants in the nematic phase, theory and simulation can be compared quantitatively. We obtain good agreement for the stiff director regime. The crossover to the flexible director regime is expected at wavelengths of the order of several thousand particle diameters, which was not accessible to our simulations.     

含氟液晶研究进展

本文简述了含氟液晶的研究进展。根据小分子含氟液晶中氟原子或含氟基团的位置不同,将其分为3类：末端是氟原子或含氟基团的液晶、苯环上氢原子被氟原子取代的液晶、中心桥键上的氢原子被氟原子取代的液晶。根据小分子含氟液晶特点,归纳了氟原子或含氟基团对液晶分子物理性质的影响。同时对高分子含氟液晶的研究进展也做了介绍。     

Halogen-Bonded Liquid Crystals

While the halogen bond has been recognised and studied for over a hundred years, it is only in more recent times that chemists have begun to apply it and see its possibilities as another supramolecular interaction that can be deployed in the preparation of materials. This review takes one of those areas, liquid crystals, and considers examples of motifs that have been deployed successfully to generate new mesogens. In particular, rather than attempting to be comprehensive, the article reviews critically data from well-characterised systems and seeks to first make some comparisons with analogous hydrogen-bonded materials, before considering how the lability and flexibility of the halogen bond expresses itself in liquid crystal behaviour.     

纤维素及其衍生物液晶研究近况

就纤维素及其衍生物溶性液晶和热致性液晶的液晶性及其影响因素,和流变性能等方面的研究作了较为详尽的综述。