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?     

A Brief Review of Carbazole-Based Photorefractive Liquid Crystalline Materials

Liquid crystals are commonplace in technological devices, such as watch and computer displays and temperature and pressure monitors. Such materials are central to our technological lifestyles. Classically, liquid crystalline materials are based on a structural motif which could be classed as rod-like (e.g. biphenyl derivatives) and in more recent times as disc-like (e.g. triphenylene derivatives). The rod-like materials are very attractive in terms of their chemical stability and their response to electric fields, both of which are a prerequisite for display devices, whereas disc-like materials show promise as one-dimensional conducting materials. Increasing scientific and technological requirements mean that new materials are continually sought to surpass the liquid crystalline materials which are presently known. Carbazole derivatives are well-known interesting natural products. Several methods have been developed and reported in the literature for the synthesis of carbazole derivatives. There are several review articles published on the photorefractive properties of carbazole-based materials. Chemical modification of the carbazole moiety to create a new class of discotic, calamitic and banana-shaped liquid crystalline materials, which will have novel and enhanced photorefractive properties over the amorphous carbazole derivatives, will be discussed in this mini review.     

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.     

分子间自组装盘状液晶材料研究进展

综述了近十年来国内外报道的分子间自组装盘状液晶的研究进展;重点阐述了通过分子间氢键或金属离子配位键自组装的盘状液晶小分子和超分子液晶的液晶性能、掺杂了无机纳米粒子的通过氢键形成的液晶材料的光电性能及其在有机光伏器件中的应用;最后总结了不同类分子间自组装盘状液晶的性能优势。综合文献报道可知,引入分子间氢键或配位键可以更好地实现盘状液晶在特定功能材料中的应用,并且自组装的盘状液晶还可与纳米粒子形成复合物,得到具有特定功能的纳米复合材料。     

五种新型高分子液晶研究进展及应用前景

阐述了高分子液晶的形成条件,综述了纤维素液晶、甲壳素液晶、铁电液晶、盘状液晶、卤代液晶等五种新型高分子液晶材料的结构、性能及其应用前景,并对高分子液晶的发展方向进行了展望。     

1,3,4-噻二唑类液晶化合物的研究进展

综述了近年来1,3,4-噻二唑类液晶化合物的研究进展,该类化合物形成棒状液晶、楔形液晶、弓形液晶、Polycatenar液晶、盘状液晶的分子结构及其自组装形成的液晶相结构。介绍了分子中末端基团、烷基链数目、刚性核长度等结构常数对液晶自组装结构的的影响。与含氧的杂环类似物1,3,4-噁二唑液晶化合物相比,1,3,4-噻二唑类液晶化合物的液晶性、光电性等更加优越。液晶方面类比表明,它具有更好的液晶性质。     

Ionic electroactive polymer actuators based on nano‐carbon electrodes

This review paper focuses on the recent studies of electroactive polymer actuators that have a triple‐layered configuration composed of an ionic‐gel electrolyte layer sandwiched by nano‐carbon dispersed ionic‐liquid gel electrode layers (bucky‐gel actuator) for the purpose of development of practical devices. The review covers recent studies of the developments of the materials of the bucky‐gel actuators and their electromechanical modeling. In the final section, the application to an ultra‐thin and ultra‐light Braille display based on the bucky‐gel actuator is described. © 2013 Society of Chemical Industry     

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。     

Versatility of photoalignment techniques: From nematics to a wide range of functional materials

Alignment methods of nematic liquid crystals (LCs) by surface photoreactions on substrate surfaces were initially proposed around 1990, and the photoalignment technology of nematic LCs has recently been integrated into the LC device fabrication industry due to its profitable features. Accumulated efforts in this field have revealed that applications of photoalignment processes are not limited to conventional nematic LCs but that a variety of functional materials can also be manipulated according to this principle. Target materials have now been extended to thermotropic smectic LCs, discotic LCs, LC polymers, block copolymers, gel networks, conjugated polymers, and organic semiconductors and lyotropic systems including chromonic LCs and inorganic–organic mesostructured hybrids. Through these photochemical approaches, many types of photopatterning for both topographical and orientational modulations have become feasible. This article reviews photoalignment processes applied to a wide range of materials, surveying relatively recent work. Some important related alignment and patterning processes are also introduced to clarify the significance of these photoalignment techniques.     

四苯基乙烯室温液晶发光材料的制备与表征

发光液晶兼具发光性能和液晶的有序性,作为一种具有重要应用前景的功能材料而受到研究人员的广泛关注。本工作采用离子自组装法制备了一种兼具聚集诱导发光和液晶性质的四苯基乙烯衍生物(TPE-Chol)。通过吸收光谱、荧光光谱和X射线衍射等实验对TPE-Chol的光物理性质和液晶结构进行了详细研究。实验结果表明,TPE-Chol在室温状态下具有液晶结构,并且表现出典型的聚集诱导发光行为,是一种新型室温液晶发光材料,在液晶显示等领域具有潜在的应用价值。     

Anisotropic films photopolymerized from aligned cross-linkable gemini ammonium liquid crystals for ion conduction

Cross-linkable gemini ionic liquid crystals are prepared by jacketing the diammonium moiety between two biphenyl benzoate mesogens. Anisotropic films are obtained by photopolymerization of the macroscopically aligned gemini ionic liquid crystals for ion conduction. Small angle X-ray scattering (SAXS) measurements indicate that the monolayer nanostructure is formed in the films and scanning electron microscope (SEM) observations reveal that the smectic layers are perpendicular to the film surface. Electrochemical impedance spectroscopy (EIS) characterization shows that the films exhibit strong anisotropy in ion conduction. The ion conduction across the film is enhanced while that within the plane of the film is impeded. The ionic conductivity in vertical direction of the film reaches up to 10⁻³ cm S⁻¹ at 180 °C and the measured anisotropy (ratio of the measured conductivities in vertical direction of the film versus in parallel to the film) is 100–350. The photopolymerization of the cross-linkable gemini ammonium liquid crystals offers excellent potential for the development of solid electrolytes for electrochemical devices. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47349.     

普通离子液体和功能化离子液体的合成研究进展

离子液体是在室温下为液体、具有离子特性的新型绿色溶剂,作为一类环境友好型的反应介质,在诸多领域有其独特的性质.综述了普通离子液体和功能化离子液体的合成研究进展,并对其前景进行了展望.     

Nano‐structured materials with low surface energies formed by polyelectrolytes and fluorinated amphiphiles (PEFA)

Polymer complexes formed by polyelectrolytes and fluorinated amphiphiles (PEFA) represent a new class of materials which can be prepared easily as nano‐structured coatings on a large number of chemically different substrates. The surface energies of PEFA coatings are remarkably low and can be adjusted in the range 6–18 m Jm⁻². Many of their physical properties, such as elastic modulus and mechanical strength, are determined by the nature of the polymer structure. By adjusting charge densities, molecular weights and the content of nonionic comonomers, a great variety of optimizations for a number of applications are possible. The amphiphiles have a decisive influence on the nano‐structure and on the surface energy of these materials. They act as building blocks, which vary in their number of fluorinated chains, their chain lengths and in the ionic head‐groups. Carboxylate, phosphate and sulfonate groups are preferred for the preparation of PEFAs. The scope of this review is to present a discussion of the mesomorphous structures (from columnar discotic to perforated lamellar), the low surface energies and attractive applications of these PEFA materials. Applications are found predominantly in low‐friction and anti‐soiling coatings. © 2000 Society of Chemical Industry     

黏土及类黏土液晶材料的研究进展

黏土矿物(clay minerals)是组成黏土岩和土壤的主要矿物,它是一种含镁、铝为主的水合硅酸盐矿物.研究发现黏土矿物液晶与有机液晶材料相比,具有光、电、磁性能强,热稳定性好,价格低廉等优点.简要介绍了黏土矿物液晶材料的形成机理,概述了片层状黏土液晶材料、纤维型黏土液晶材料、类黏土矿物液晶材料的制备方法和研究现状,同时介绍了不同条件(浓度、离子强度、外电场作用、分散介质、重力作用)对黏土及类黏土分散体系相变的影响,并对黏土矿物液晶材料的应用发展前景进行了概述.     

基于苯并噻二唑液晶化合物的研究进展

2,1,3-苯并噻二唑(BTD)类化合物具有优异的光电性能,被广泛应用于有机光电领域。合成具有液晶性的苯并噻二唑类衍生物可以达到改善这类化合物的光电性能的目的。综述了近年来苯并噻二唑类液晶化合物的研究进展,包括含单个苯并噻二唑单元的非对称和对称液晶及含两个苯并噻二唑单元的液晶。介绍了该类化合物的分子结构、液晶自组装行为以及光电性能之间的关系。最后,对苯并噻二唑类液晶化合物研究现状进行了总结,指出当前研究所存在的局限性,并对未来该类液晶化合物的分子设计和发展前景进行了展望。     

Liquid Crystals in Tribology

Two decades ago, the literature dealing with the possible applications of low molar mass liquid crystals, also called monomer liquid crystals (MLCs), only included about 50 references. Today, thousands of papers, conference reports, books or book chapters and patents refer to the study and applications of MLCs as lubricants and lubricant additives and efforts are made to develop new commercial applications. The development of more efficient lubricants is of paramount technological and economic relevance as it is estimated that half the energy consumption is dissipated as friction. MLCs have shown their ability to form ordered boundary layers with good load-carrying capacity and to lower the friction coefficients, wear rates and contact temperature of sliding surfaces, thus contributing to increase the components service life and to save energy. This review includes the use of MLCs in lubrication, and dispersions of MLCs in conventional polymers (PDMLCs). Finally, new lubricating system composed of MLC blends with surfactants, ionic liquids or nanophases are considered.     

偶氮液晶化合物的研究进展

偶氮液晶化合物是一类非常重要的功能材料。在光和热的作用下,偶氮液晶化合物会出现顺反异构现象。该类化合物既有光色效应,又有光致双折射效应,因此,偶氮液晶化合物不仅在信息材料领域具有潜在的应用前景,而且还是制备分子开关器件的首选对象。综述了近年来常见偶氮液晶化合物的发展概况,并概述了该类化合物的分类。     

四氟硼酸盐类离子液体对典型柴油的萃取脱硫研究

The extractive removal of sulfur compounds （S-compounds） from Dongying and Liaohe diesel fuels with [BF4]^--based ionic liquids were systematically investigated. The results show that the absorption capacity of an ionic liquid for the S-compounds in diesel fuels relies on its structure and its size. In the case of the two examined diesel fuels, both elongating the cation tail length and increasing the mass ratio of ionic liquid/diesel fuel promote the desulfurization ability of the examined ionic liquids. The results also show that imidazolium-based ionic liquids display higher extraction efficiencies than pyridinium-based ionic liquids, presumably owing to the fact that the rings of the S-compounds are similar to the imidazolium head ring. With the 1 ： 1 mass ratio of ionic liquid/diesel fuel, the rates of the first desulfurization of Dongying and Liaohe diesel fuels using [C8mim][BF4] amount to 29.96% and 39.76%, suggesting that [C8mim][BF4] is a promising extractant for desulfurization of these diesel fuels.     

氧化石墨烯液晶相结构的调控及应用进展

氧化石墨烯液晶（GOLCs）是氧化石墨烯薄片分散在水或极性有机溶剂中形成的宏观介晶有序、微观各向异性的液晶相,在自组装膜、储能、液晶显示器和超强纤维等领域展现良好的应用前景。本文首先介绍了氧化石墨烯液晶具有向列相、层状相和手性相等结构特征;具体综述了氧化石墨烯液晶相变的影响因素、调控途径及其原理,包括氧化石墨烯的尺寸及其分布、氧化石墨烯的氧化程度、氧化石墨烯在溶液中的质量/体积分数、溶剂的极性、溶液的pH以及添加盐的种类、浓度,外界施加的电场或磁场;最后简单介绍了氧化石墨烯液晶在电化学及其他方面的潜在应用。本文为调控氧化石墨烯液晶的相结构、开发多功能氧化石墨烯液晶及拓宽氧化石墨烯液晶的应用领域提供了理论指导。