高分子胆甾相液晶盘状聚集体的结构分析

利用偏光显微镜,对乙基纤维素/二氯乙酸(EC/DCA)胆甾相液晶的织构进行了研究。当EC/DCA液晶溶液处于两相共存状态时,可以观察到一种典型的胆甾相液晶织构形式——盘状聚集体。结合有效偶极矩模型,推断了分子链在盘状聚集体中的排列方式及盘状聚集体的二维等速生长性质。     

侧链胆甾液晶聚合物的合成及性能

合成了一种新型胆甾液晶单体(M1)和一种向列液晶单体(M2),通过与聚硅氧烷(PMHS)接枝共聚得到了系列侧链液晶聚合物P1~P6,通过傅立叶变换红外光谱(FT-IR)、差示扫描量热仪(DSC)、热失重分析(TGA)、偏光显微镜(POM)等手段对聚合物的结构、液晶性能及热性能进行了表征。随着胆甾液晶基元的减少,其玻璃化转变温度(Tg)、清亮点(Ti)逐渐降低。聚合物P1~P6均为胆甾型热致液晶,聚合物呈现出典型的胆甾液晶彩色Grand-jean织构、油丝及焦锥织构,并且颜色随温度升高发生变化。     

胆甾型液晶的热光效应及其在温度测量中的应用

前言液晶,由于其具有特殊的功能,在近二十年来得到了迅速的发展。六十年代以前,对液晶的研究只限于理论方面。目前,由于综合性学科的发展,具有各向异性的低分子液晶作为一种新型材料,获得了广泛的应用。液晶按光学织构可分为三种介晶相:(1)近晶相;(2)向列相;(3)胆甾相,具有这三种介晶相的液晶均属于热致型液晶。其中胆甾相液晶是最早开发的一种,由于它对温度变化反应的迅速,在不同温度下显现不同颜色,因此可用来制造热显示器,用以测量     

乙基纤维素液晶共混膜的结构与富氧性能

研究了乙基纤维素(EC)的二氯乙酸或冰乙酸溶液液晶结构及溶液浇铸EC/低分子液晶共混膜的结构与富氧性能。结果表明,EC的溶致液晶态呈现Maltese黑十字消光的球晶形态,而且球晶上带有同心圆环的规则指纹结构,有时也呈现无规指纹结构(胆甾液晶特征结构);电场的施加或低分子液晶含量的加大,可使氧气透过系数显著加大,而温度上升却使氧气透过系数和氧氮分离系数同时加大。     

几种热致液晶性纤维素衍生物的制备及性能的研究

以纤维素或羟乙基纤维素为原料，通过酯化反应制备了乙酰氧乙基纤维素（ＡＥＣ）、苯甲酰氧乙基纤维素（Ｂ２ＥＣ）和苯甲酰氧纤维素（Ｂ２Ｃ）。采用ＦＴ－ＩＲ和元素分析表征了产物结构，通过用ＤＳＣ、ＨＳＰＬＭ和ＷＡＸＤ研究了产物的致热液晶织构和性能。Ｂ２Ｃ的热致液晶性最强，其各向同性液态转变温度（ＴＬＩ＝８２℃）和转变热焓（ΔＨＬＩ＝１４．８８Ｊ／ｇ）是迄今报导的热致液晶纤维素衍生物中最高的。     

液晶多肽及其应用研究

基于国内外最新研究文献,系统论述了近年来液晶多肽的大分子链结构、液晶性能及应用前景等方面的研究进展。指出液晶多肽在一定条件下将出现各向同性态到各向异性态的可逆转变,伴随着大分子链从线圈状到螺旋状的可逆转变。聚[γ－苄基－L－谷氨酸酯]有序度参数可达0.875。二次谐波的产生证明了有些液晶多肽呈现奇异的胆甾相结构,其胆甾相由极性向列型片晶组成,且分子偶极矩和长轴方向平行。多肽既可显示溶致液晶性又可显示热致液晶性,其液晶相多为胆甾型,有时呈向列型。外加场如取向场及电场对多肽的液晶性也会产生强烈影响。液晶多肽可加工成液晶态水凝胶、纤维和薄膜等,可望用作全息照相材料、光学元件、彩色滤色器以及溶致液晶电池等。     

乙基氰乙基纤维素/甲基丙烯酸酯液晶溶液的研究EI

乙基氰乙基纤维素/甲基丙烯酸酯在一定的浓度下可以形成溶致性液晶,从液晶相的双折射纹理结构和小角光散射的H_v散射花样可知这类液晶是胆甾型的。同时,在液晶相开始出现时及各向同性完全消失时的临界浓度C_1~*和C_2~*均随着甲基丙烯酸酯基的链的增长而减少。     

羟丙基纤维素液晶的肝素化及其抗凝血性能研究

羟丙基纤维素(HPC)经过辛酰化和丙烯酰化反应得到一种新型的辛酰化/丙烯酰化的羟丙基纤维素液晶材料(OPPC),然后利用Micheal加成机理在其表面接枝肝素。傅里叶变换红外光谱表明OPPC膜表面已实现肝素化改性,甲苯胺蓝法测得肝素接枝量为9.42μg/cm2;偏光显微镜观察证实肝素化后OPPC膜在室温下仍呈现胆甾型液晶织构;肝素化的OPPC膜亲水性得到改善,而溶血率和血小板粘附实验证明肝素功能化的液晶膜具有良好的血液相容性。     

聚硅氧烷类手性偶氮液晶高分子的制备

合成了一种含胆甾醇基元的手性液晶单体4-烯丙氧基苯甲酰氧基异丙酰氧基胆甾基酯(M)和一种含偶氮基元的液晶单体4-烯丙氧基苯甲酰氧基异丙酰氧基偶氮苯甲酸乙酯(N),将它们与含氢聚硅氧烷接枝共聚,得到侧链手性偶氮液晶聚合物PA1~PA6。通过红外、核磁共振、旋光仪、偏光显微镜、差示扫描量热和X射线衍射等手段对所合成单体及聚合物的结构和液晶相行为进行了表征。结果表明,单体M具有胆甾相的油丝织构,单体N具有向列相的纹影织构,聚合物PA1~PA6呈现胆甾相的Grandjean织构,它们的热稳定性好,液晶区间宽达171~180℃之间。     

胆甾型侧链液晶共聚砜热转变温度的调节

采用壬烯－１与胆甾型液晶烯类单体，二氧化太进行自由基共聚合的方法来调节胆甾型侧链液晶共聚砜的热转变温度。研究内容包括：胆甾型侧链液晶共聚砜的合成、表征及性能测试。研究结果表明，该共聚砜的两个液晶转变温度均随其中壬烯－１单体单元组份含量的增加而降低。     

Chiral photonic materials self-assembled by cellulose nanocrystals

Cellulose nanocrystals are natural nanomaterials with a high aspect ratio, high specific area, excellent stability, and favorable optical performances. Cellulose nanocrystals can form cholesteric liquid crystals through a left-handed spiral arrangement. The suspension liquid of cellulose nanocrystals can retain the chiral cholesteric structure in the solid film after being completely dried, leading to the appearance of Bragg reflection and bright structural color in the visible spectrum. By changing the conditions or mixing with polymers, the cellulose nanocrystals film will show different structural colors due to the change of pitch. The film can cover almost the entire visible spectrum, which can be applied to various aspects such as sensing, anti-counterfeiting, detection, and so on. In this review, we elaborated on the synthesis and properties of cellulose nanocrystals materials and introduced the mechanism of structural color formation, as well as the current research progress and applications. Cellulose nanocrystals have become a hot spot in the field of structural color, and provide more research value for providing a cheap, easy-to-obtain, green-friendly, and high-biocompatibility natural photonic material.     

Studies of the bistable mechanism in electro-thermal switching polymer-stabilized cholesteric texture light shutters

Our research studied the bistable mechanism in electro-thermal switching reverse polymer-stabilized cholesteric texture (ET-RPSCT) light shutters. The bistable mechanism in ET-RPSCT is a result of a polymer distortion effect induced by applying a high-voltage pulse. It was found that long-pitch cholesteric liquid crystals will maintain a focal conic texture by a distorted polymer network which exhibits a translucent state. An annealing treatment method was used to recover cholesteric liquid crystals back to the planar texture through alignment layers. We compared the ET-RPSCT cells in different polymer network structures, which were built from different UV curable diacrylate monomers and concentrations, resulting in different anchoring forces and polymer distortion effects. We found that when the polymer network structure is tight and fiber-like, the long-pitch cholesteric liquid crystals are more stable in the focal conic texture because of polymer distortion, and are resistant to switching states. On the other hand, the long-pitch cholesteric liquid crystals recover to the planar texture easily by thermal switching due to a loose and grain-like polymer network structure. Furthermore, the effects of polymer structure on the electro-optical performance of ET-RPSCT were also investigated.     

Dynamic Spirals of Nanoparticles in Light‐Responsive Polygonal Fields

Nanoparticles tend to aggregate once integrated into soft matter and consequently, self‐assembling nanoparticles into large‐scale, regular, well‐defined, and ultimately chiral patterns remains an ongoing challenge toward the design and realization of organized superstructures of nanoparticles. The patterns of nanoparticles that are reported in liquid crystals so far are all static, and this lack of responsiveness extends to assemblies of nanoparticles formed in topological singularities and other localized structures of anisotropic matter. Here, it is shown that gold nanoparticles form spiral superstructures in polygonal fields of cholesteric liquid crystals. Moreover, when the cholesteric liquid crystals incorporate molecular photoswitches in their composition, the pitch of the nanoparticulate spirals follows the light‐induced reorganization of the cholesteric liquid crystals. These experimental findings indicate that chiral liquid crystals can be used as chiral and dynamic templates for soft photonic nanomaterials. Controlling the geometry of these spirals of nanoparticles will ultimately allow modulating the plasmonic signature of hybrid and chiral systems.     

Cholesteric Liquid Crystals for Color Information Technology

Fixation of the molecular ordering of cholesteric liquid crystals is essential for use of these materials in color information technology. Methods to achieve this as well as thermal and photochemical control of the cholesteric pitch of the liquid crystals are addressed and applications in rewritable color recording are highlighted. The Figure shows a sample recorded using a laser.     

不同相态液晶添加剂的润滑性能及机理分析

为了研究液晶化合物作为润滑添加剂的摩擦学性能及其作用机理,考察了2种向列相液晶和2种胆笛相液晶在矿物基础油中的摩擦学性能,比较了不同结构添加剂抗磨减摩性能的差异并分析了原因,在此基础上简述了液晶化合物的不同相态对于润滑性能的作用机理。结果表明:加入1%的液晶添加剂均可明显改善基础油的润滑性能;向列相液晶添加剂由于分子结构刚性更强,利于增加油膜强度以避免干摩擦产生;而胆备相液晶添加剂分子呈片层、螺旋结构,柔性链易适应磨痕,在同等载荷下有着更好的抗磨效果。     

Defects in liquid crystals (II)

Defects in the disordered (uniaxial) liquid crystals, nematic, smecticA and cholesteric, and the use of topological analysis in classifying them, are discussed. While the latter is very successful in classifying defects in nematics, it fails to do so in the case of smecticA and cholesteric liquid crystals because of geometrical constraints. However, topological arguments have been partially successful in predicting some of the defects in cholesterics. The known features of the isotropic (cubic and amorphous) cholesteric blue phases are summarised and the various theoretical models picturing them as defect lattices, are also discussed briefly.     

Hydrodynamics of cholesteric liquid crystals in the coarse-grained limit

The hydrodynamical behaviour of cholesteric liquid crystals has been considered in the limit of low amplitude and low frequency distortions and motions. It is shown that there are interesting analogies with superfluid-hydrodynamics, such as the fountain effect, thermal superconductivity and temperature wave propagation. In certain situations, there is an unusual formation of a boundary layer at low velocities, and in certain others the properties resemble those of percolation in porous media. Results concerning some special phenomena peculiar to cholesteric liquid crystals are also presented. Finally it is pointed out that there should be two types of second sound in chiral smectic C.     

Anwendung Flüssiger Kristalle in der Materialprüfung

Application of Liquid Crystals for Materials Testing. Cholesteric liquid crystals are recently known to be suitable for temperature measurement which can be done by observation of colour variation created by the layers of the cholesteric liquid crystals. The main advantages of liquid crystals over conventional temperature measurement are their low thermal capacity and the possibility of showing large temperature maps. By the cinematographic method the variation of temperature maps as a function of time can be recorded. Until now those informations were received only by relativly costly equipment i. e. infrared cameras.     

Tunable lasing from a cholesteric liquid crystal film embedded with a liquid crystal nanopore network

Continuous tuning of lasing wavelength is achieved in cholesteric liquid crystal lasers by embedding a network of nanopores with an average size of 10 nm filled with liquid crystals inside a polymerized matrix with helical order. The device possesses both high transparency and a fast response time because the tuning is driven by local reorientation of the liquid crystal molecules in the nanopores.