Liquid Crystalline Inorganic Nanosheet Colloids Derived From Layered Materials

Inorganic layered crystals such as clay minerals, layered niobates, and graphite are exfoliated in solvents to form colloidal dispersions of extremely thin inorganic nanosheets. Recently, the liquid crystal phases of these “nanosheet colloids” have been rediscovered and are attracting interest as new types of inorganic liquid crystals. The huge anisotropy of the mesogenic nanosheets compared to other liquid crystal systems is an important feature of the nanosheet liquid crystals for fundamental studies in the fields of colloid science and soft matter physics. In addition, the rich functionalities intrinsic to inorganic materials open a variety of applications such as smart colloids and composite materials with structural regularity. In this article, the recent progress of the emerging new materials of inorganic nanosheet liquid crystals is reviewed with a focus on the behaviors of each system, alignment by external field, and theoretical aspects.     

Ionic Discotic Liquid Crystals

Ionic discotic liquid crystals are salts of discotic liquid crystals that may display lyotropic and thermotropic mesomorphism. Columnar structures of π-π stacking ionic discotic liquid crystals function not only as anisotropic organic semiconductors, similar to their neutral analogues, but they may also efficiently conduct ions. This combination of electronic and ionic conduction is only one of several unique properties that these materials may display, but their systematic investigation has been limited because of their often complex synthesis, purification, and characterization. However, a comprehensive account of existing reports on ionic discotic liquid crystals is not straightforward, despite their relatively small number, because publications are scattered across different areas of research, such as liquid crystals, ionic liquids, and ionic self-assembly. This review intends to provide a concise but comprehensive overview of the published work on ionic discotic liquid crystals and related compounds and is expected to stimulate further exploration. Highlighted in this review is the mesomorphism of ionic discotic liquid crystals and its dependence on structural changes, which is also the focus of most reported studies. Particular attention was given to the dependence of mesomorphism on the location and types of the charged groups as these are parameters unique to these compounds. Also described are electronic, optical, and other properties of these materials if reported.     

Dielectric and Electro-Optical Properties of Antiferroelectric Liquid Crystalline Materials

Antiferroelectric liquid crystals (AFLCs) are a recent class of materials in the family of liquid crystals which have high prospect of application in displays with better results as compared to conventional nematic displays. Beside technological applications, AFLCs are very interesting from the point of view of basic studies in soft condensed matter systems as these materials are showing various new sub-phases, viz. SmC_α^*, SmC_β^*, SmC_γ^* and many others with distinct macroscopic properties in a narrow temperature region in addition to the most common wide-range low-temperature SmC_a^* phase. In the present article, we report the structure of various sub-phases of AFLCs, their dielectric behaviour and the electro-optical response of some of the materials studied by our group.     

含有二氟亚甲氧基连接基团液晶化合物合成方法进展

含有二氟亚甲氧基连接基团的液晶化合物由于其本身特别的结构而具有低的旋转粘度(γ1)、高的介电各向异性(Δε)、低温下与其他液晶良好的互溶性、适当的光学各向异性(Δn),是快速响应TN、IPS、FFS-TFT等多种显示类型液晶混合物的必备成分,但是其合成难度较大、成本较高。叙述了文献公开的多种合成方法,以关键原材料分类,可分为酯、酸、酮、易形成碳负离子的芳基衍生物4类方法,分析了各类方法的优缺点以及适用范围,详述了部分方法不同取代基对结果的影响。     

The Effect of Liquid Crystalline Structures on Antiseizure Properties of Aqueous Solutions of Ethoxylated Alcohols

Aqueous solutions of ethoxylated alcohols which form lyotropic liquid crystals at high concentrations (40–80%) were selected as model lubricating substances. Microscopic studies under polarized light and viscosity measurements were carried out in order to confirm the presence of liquid crystalline structures in the case of alcohol solutions with ethoxylation degrees of 3, 5, 7 and 10. Microscopic images and viscosity coefficient values characteristic of various mesophases were obtained. As expected, the viscosity of LLCs decreases considerably with an increase in shearing rate which is characteristic of liquid crystals being non-Newtonian liquids. Antiseizure properties were determined by means of a four-ball machine (T-02 Tester) and characterized by scuffing load (P_t), seizure load (P_oz) and limiting pressure of seizure (p_oz). Alcohol ethoxylates forming mesophases in aqueous solutions have the strongest effect on the P_t values which are several times higher than those measured in the presence of water. Ethoxylates with higher degrees of ethoxylation exhibit higher values of scuffing load. Those changes have been interpreted as a result of higher cloud points at which those compounds lose their amphiphilic properties. In general, the presence of mesophases in the bulk phase and particularly in the surface phase may lead to the formation of a lubricant film which separates the frictionally cooperating elements of a friction pair. The antiseizure efficiency of alcohol solutions is highest up to the load value which does not exceed the scuffing load value.     

Nano-Segregation and Directed Self-Assembly in the Formation of Functional Liquid Crystals

It is often a question that is asked: “How can you predict from the molecular architecture of a material the structure of the condensed phases it forms, and what properties would you expect the phase to exhibit?” For liquid crystals, knowing how to design materials for particular applications requires precision molecular engineering. In this article we examine how molecular topology and interactions influence phase formation and report on material design.     

A QCM‐D and SAXS Study of the Interaction of Functionalised Lyotropic Liquid Crystalline Lipid Nanoparticles with siRNA

Biophysical studies were undertaken to investigate the binding and release of short interfering ribonucleic acid (siRNA) from lyotropic liquid crystalline lipid nanoparticles (LNPs) by using a quartz crystal microbalance (QCM). These carriers are based on phytantriol (Phy) and the cationic lipid DOTAP (1,2‐dioleoyloxy‐3‐(trimethylammonium)propane). The nonlamellar phase LNPs were tethered to the surface of the QCM chip for analysis based on biotin–neutravidin binding, which enabled the controlled deposition of siRNA–LNP complexes with different lipid/siRNA charge ratios on a QCM‐D crystal sensor. The binding and release of biomolecules such as siRNA from LNPs was demonstrated to be reliably characterised by this technique. Essential physicochemical parameters of the cationic LNP/siRNA lipoplexes—such as particle size, lyotropic phase behaviour, cytotoxicity, gene silencing and uptake efficiency—were also assessed. The SAXS data show that when the pH was lowered to 5.5 the structure of the lipoplexes did not change, thus indicating that the acidic conditions of the endosome were not a significant factor in the release of siRNA from the cationic lipidic carriers.     

Liquid Crystalline Polymers

Abstract

In this article emphasis will be placed on selectively from 45 papers presented at the spring meeting and 33 papers also presented at the fall meeting.     

Some recent developments in polysilane chemistry

(I) Ordered and disordered polysilane copolymers: Condensation of ClSiMe₂Si(n-Hex)₂SiMe₂Cl with Na/K in toluene at 90°C produced a polymer with a strongly bimodal molecular weight distribution. The high-M _w and low-M _w portions were separated by fractional precipitation with 2-propanol, and the properties of the two fractions were investigated.²⁹Si-NMR spectra show that the low-M _w fraction is fully ordered but the high-M _w fraction is randomized. (II) Liquid crystalline polysilanes: Condensation ofn-Bu(n-Hex)SiCl₂ with Na in toluene led to a homopolymer which is a rubbery solid at 25°C. The polymer undergoes a second-order transition at –45°C and a first-order (melt) transition at –20°C. X-ray diffraction shows that the polymer has the same structure, a columnar hexagonal lattice, in all three phases; from –20 to >200°C, it exists in a columnar liquid crystalline mesophase. Similar hexagonal mesophases were observed at 25°C for the family of copolymers, (n-Hex₂Si) _n (Alk₂Si) _m , Alk =n-Pentyl,n-Bu,n-Pr, Et, Me.     

Ferrocene-containing Liquid Crystalline Polymers

This article is one of a number of reviews in a special issue to honor Prof. Dr. Ian Manners of the University of Bristol, UK, for his outstanding contributions in the field of organometallic polymers. The focus of this review is on the syntheses, properties, and characterization of ferrocene-containing liquid crystalline polymers in which ferrocene moieties are in or pendent to the backbone and also dendrimers and [60]fullerene-ferrocene liquid crystalline materials.     

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.     

功能液晶聚酯

综述了新型功能液日聚酯材料的大分子链结构、液晶相变温度与应用前景。这类功能液晶聚酯或者其主链含有大量碳碳双键,或者其侧链上含有大量氟碳链节或偶氮链节。功能液日聚酯的玻璃化转变温度和液日相变温度通常比传统高强度、高模量液日聚酯要低,尤其具有高强度、高模量液晶聚酯所不具备的特殊性能,如交联化、凝胶和感光作用,使其可以作为全息储存膜和其他功能材料。     

Functional Discotic Liquid Crystals

This review article provides a bird’s-eye view on discotic liquid crystals and their potential applications. Design principles, synthesis, modification of physical properties and potential applications of some common discotic liquid crystals have been briefly summarized.     

液晶的织构与表征

液晶具有晶体分子排列的有序性和光学各向异性,液晶独特性在于它对外界因素如热、磁、光等都非常敏感,使其结构发生变化,其功能也发生相应的变化。在当今科技中有着非常广泛的应用。本文对液晶的分类,液晶的织构和液晶的表征方法及手段等方面进了具体的阐述。     

Key Developments in Ionic Liquid Crystals

Ionic liquid crystals are materials that combine the classes of liquid crystals and ionic liquids. The first one is based on the multi-billion-dollar flat panel display industry, whilst the latter quickly developed in the past decades into a family of highly-tunable non-volatile solvents. The combination yields materials with a unique set of properties, but also with many challenges ahead. In this review, we provide an overview of the key concepts in ionic liquid crystals, particularly from a molecular perspective. What are the important molecular parameters that determine the phase behavior? How should they be introduced into the molecules? Finally, which other tools does one have to realize specific properties in the material?     

新型液晶离聚物研究进展

液晶离聚物是一种具有液晶聚合物和离子聚合物双重特性的一类高聚物.液晶离聚物不仅显示溶致和/或热致液晶性,而且具有一些特殊的功能性.本文基于国内外最新研究文献,论述近年来合成的五类液晶离聚物的液晶行为及应用前景.     

纤维素在多聚磷酸中的液晶性

讨论了纤维素在多聚磷酸溶液中的溶解情况和液晶性。采用适当的配比,纤维素能够溶解于多聚磷酸并形成各向异性溶液,在偏振光显微镜下可观察到彩色图片。溶液温度、纤维素聚合度、纤维素浓度对液晶性均有影响。溶液受热后,彩色图像会消失。     

Oxidative Desulfurization‐Fluorination: A Facile Entry to a Wide Variety of Organofluorine Compounds Leading to Novel Liquid‐Crystalline Materials

The oxidative desulfurization‐fluorination reaction of organosulfur compounds using an N‐haloimide and a fluoride source is demonstrated to be an effective and mild fluorinaton method that allows us to synthesize in high yields with high chemoselectivity various types of gem‐difluoro compounds, trifluoromethyl‐substituted (hetero)aromatics, trifluoromethyl ethers, and N‐trifluoromethylanilines. Herein briefly summarized are the synthetic procedures as well as the scope and limitations of the reaction. The applicability of the reaction is demonstrated by the synthesis of a difluorinated glutamic acid and novel liquid‐crystalline materials having an N‐trifluoromethylamino, trifluoromethoxy, or 1,2‐difluoroethylene group. The fluorine‐containing liquid‐crystalline materials are compared with the corresponding non‐fluorinated materials in respect to phase transition behaviors and electro‐optical properties and shown to be suitable for not only super twisted nematic (STN) but also for thin film transistor (TFT)‐addressed liquid crystals displays. 1. Introduction 2. Fluorination Reactions 2.1 Fluorination of Sulfides and Thiols 2.2 Fluorination of Dithioacetals 2.3 Oxidative Desulfurization‐Fluorination of Dithioester and Orthothioester 2.4 Synthesis of Trifluoromethyl Ethers from Dithiocarbonates 2.5 Oxidative Desulfurization‐Fluorination of Thionesters and Thioncarbonates 2.6 Synthesis of Trifluoromethylamines from Dithiocarbamates 3. Synthesis and Electro‐Optical Properties of Novel Fluorine‐Containing Liquid Crystals 3.1 Synthesis and Electro‐Optical Properties of N‐Trifluoromethylamino‐Substituted Liquid Crystals 3.2 Syntheses and Electro‐Optical Properties of Liquid Crystals having Trifluoromethoxy Polar Functional Group 3.3 Synthesis and Properties of 3‐Substituted Phenyl Trifluoromethyl Ethers 3.4 Synthesis and Electro‐Optical Properties of Liquid Crystals with a vic‐Difluoro‐Olefinic Moiety     

热致液晶聚合物的热增强及应用

基于各种正式发表的文献 ,澄清了热致液晶聚合物发展过程中的一些问题 ,并对各种形式热致液晶聚合物的热增强属性作一系统阐述。     

胆甾醇乙酸酯液晶的合成

采用胆甾醇与乙酸酐直接酯化法合成胆甾醇乙酸酯，优化后的工艺条件为：n(乙酸酐)：n(胆甾醇)＝1．9-2．0：1，反应温度80℃，反应时间3h，在此条件下，产率可达95％以上；经无水乙醇重结晶，纯度达99％以上。产品的熔点为97．5℃，清亮点为113℃，IR谱图分析和元素分析结果表明，产物纯度较高。