新的手性Schiff碱液晶的合成及变温红外光谱研究(Ⅰ)

合成了1个新的手性Schiff碱类液晶并以DSC、偏光显微镜及变温红外光谱等手段对其热致相变过程进行了研究。     

两个新的氢键诱导液晶化合物的合成

通过４－丁氧基苯甲酸（４ＢＡ０与两个手性取代的苯乙烯基吡啶（ＶＳＺ及ＬＳＺ）间的氢键作用合成了２个新的液晶化合物，用ＤＳＣ、偏光显微镜研究了其液晶行为，并由红外光谱证实了分子间氢键的存在，形成的复合物４ＢＡ－ＶＳＺ具有手性近晶Ｃ相。     

碳纳米管掺杂液晶复合材料的研究进展

近年来,许多研究者试图将液晶高分子和纳米材料二者通过物理掺杂或化学接枝的方法混合,构建有序的有机/无机杂合体,该类杂合体系除表现出各组分自身的性质外,更由于它们间的相互作用而展现出新的特性。目前,研究的主要方向是通过掺杂纳米材料来提高液晶材料性能。本文论述了 CNT掺杂液晶复合材料的研究进展,按照液晶类型不同可以分为铁电液晶、向列型液晶、盘状液晶以及液晶高分子,考察了 CNT在液晶分子中的排列,CNT对液晶的相转变温度的影响,以及对复合材料光电性能和导电性能的影响。     

聚合物分散液晶(PDLC)材料的光聚合反应

以Ar⁺激光器为光源, 采用虎红、N-苯基甘氨酸、二季戊四醇羟基五丙烯酸酯和乙烯基吡咯烷酮分别作为光引发剂、共引发剂、预聚物和稀释剂, 与液晶材料TEB30A结合, 通过光聚合反应, 制备了聚合物分散液晶(PDLC), 用紫外光谱和荧光光谱对其反应机理进行了分析. 实验结果表明, PDLC是通过光引发剂吸收光子能量后与共引发剂相互作用, 形成自由基中间体并引发聚合反应, 使预聚物与液晶产生相分离形成的.     

Reduction of Entrained Hydroxy Species in Ormosil Films for Integrated Optics

Organically modified silicates (ormosils) have been viewed as possible materials for optical signal processing devices for communications networks. One significant problem obstructing their use in this application is the absorption of infrared light by hydroxy species (present for example in silanol groups (SiOH) and water) around the communications wavelengths (1310 and 1550 nm). We have investigated several ormosil compositions, synthesised via an aqueous sol-gel method, to determine if residual hydroxy groups can be removed more effectively via reducing the connectivity of the material by increasing the number of organic groups (such as Si—CH₃). Furthermore, we have investigated the effect of different inert atmospheres on the drying process. It was found that reducing the connectivity does promote the removal of hydroxy absorption, mainly via the condensation of residual silanol groups, but also by removal of residual water, depending on the other precursors in the system. It was also found that the drying atmosphere used (nitrogen or helium) had no effect on the drying process.     

液晶基元直接横挂于主链上的液晶共聚物研究

以含有液晶基元的单体,２,５－双（４－甲氧基苯甲酰氧基）苯乙烯与丙烯醇,通过自由基共聚合反应,首次合成了一系列含液晶性单体和非液晶性单体两种结构的共聚物．采用ＤＳＣ、偏光显微镜和Ｘ－衍射方法研究了共聚物的液晶行为,发现单体和所有的共聚物均有明显的热致液晶性及较宽的液晶态温度范围;随共聚物中液晶性单体含量增加,共聚物玻璃化转变温度Ｔｇ和热分解温度Ｔｄ有所上升,但Ｔｇ的变化较小．     

Optical measurement of flexoelectric polarisation change in liquid crystals doped with bent-core molecules using hybrid-aligned structure

We proposed an optical measurement method for determination of flexoelectric polarisation change in liquid crystals (LCs), which can be induced in highly distorted LC geometries. A hybrid-aligned nematic LC (NLC) mode was introduced to evaluate the direction and magnitude of the flexoelectric polarisation. We measured the DC offset amounts for equivalent brightness levels between forward and reverse bias vertical electric fields to estimate the sign and magnitude of e_s?e_b of flexoelectric coefficients. Additionally, the optical incident angle (α_max) for the maximum effective birefringence was investigated to predict the depth distribution of the LC director affecting the magnitude of the flexoelectric polarisation. The relationship between the variations of the DC offset and α_max by the flexoelectric polarisation changes was examined using the NLC mixtures doped with three selected bent-core LCs.     

液晶性芳香酰胺化合物的合成

合成了一系列炖粹以酰胺基为中心桥键的刚性芳香酰胺小分子化合物，并对其作了表征，发现其中有些化合物具有液晶性。酰胺键之间能形成很强的分子间氢键，使芳香酰胺小分子化合物的熔点很高，难于形成液成液晶态。研究发现，如果在这类化合物的中心苯环上引入合适的取代基以减弱分子间氢键，同时引入合适的末端基时，则可使芳香酰胺化合物生成液晶相的能力增强。     

Hybrid Strip-Loaded Waveguides on Silicon Substrates

In this contribution we report on the preliminary results of synthesis and characterization of both planar and strip-loaded waveguides on silicon substrates. All the layers (buffer, guiding and cladding) have been grown by one step spin-coating process using hybrid organic/inorganic sol-gel route. Their thickness ranges from less than 1 m, for the cladding layer, up to 4 m, for the buffer one. The refractive index of the different planar waveguides were measured by means of m-line technique. Layer interfaces have been investigated with secondary ion mass spectroscopy (SIMS). Photolithography and reactive ion etching (RIE) technique have been employed to pattern the strip-loaded structures. Optical and scanning electron microscopy analysis was performed to evaluate their shape. Preliminary longitudinal transmission measurements for strip-loaded waveguides are also reported.     

Synthesis and characterisation of biodegradable liquid crystal elastomer with the property of shape recovery

Novel shape recovery biodegradable liquid crystal (LC) elastomer is reported here for the first time. The method of synthesis of the shape memory biodegradable LC elastomer has been explored. During the reaction, the LC molecules are added to form LC polymers, and then cross-linking agent is added to form a cross-linked LC elastomer. The LC elastomer in this work is hydrophilic. In vitro degradation of the LC elastomer films in a buffer of pH 7.4 at 37°C shows that the LC elastomer has good degradability. The biodegradable LC elastomer exhibits liquid crystalline behaviour and has shape memory ability. Its shape memory and actuating properties also have been studied. The reversible transition from liquid crystalline phase to isotropic phase is utilised as the switching mechanism for these stimuli-responsive materials. When reheating the LC elastomer to 120°C, the shape will recover.     

Electrically controllable smart window with greyscale based on polymer-stabilised cholesteric texture films

The study reports a novel liquid crystal (LC) film that can be applied on the transmissive substrates or stuck on existing casement window to upgrade the shield. The shadow area and transmittance can be adjusted according to the condition of the outer sunshine. The window is energy saving for which maintains the transmittance after a once-off operation of pulse amplitude modulation (PAM) electric driving. Such a film can be applied in smart curtain, display frame edge and other transmissive electro-optical devices.     

The effect of voltage controlled orientation order of liquid crystals in non-acrylic polymer dispersed liquid crystals films

The nematic liquid crystals (LCs) are randomly dispersed material with random orientation order in polymer dispersed liquid crystal (PDLC) films. The LCs change their orientation from random to vertical as electric field is applied. This transformation of orientation order of nematic liquid crystals in the PDLC films is controlled by many factors operating simultaneously. For instance, some factors like the internal forces of attractions among the neighboring LC molecules, anchoring with polymeric matrix, ITO glass boundaries, and chemical structures of the materials are less studied. The learning of extent of vertical orientation of liquid crystal droplets in an electric field is essential to attain optimum electro optical properties of PDLCs. In this finding, bipolar and radial LCs droplets with random orientation have been observed in non-acrylic polymeric media. It is learned that with small increase of contents of external material, the extent of vertical orientation has been varied intensely. The extent of vertical orientation of LCs molecules increases as the contents of external non-acrylic polymeric material decreased. For this study, the orientations of LCs with respect to material type/contents, external applied force, and restoration of electric filed as hysteresis have been studied in details.     

Advanced electro-optical smart window based on PSLC using a photoconductive TiOPc electrode

This study demonstrates an electro-optical controllable smart window based on a liquid crystal device. The device integrates a photoconductive electrode based on TiOPc films into a liquid crystal shutter based on polymer-stabilised homeotropic aligned nematic liquid crystals (PSLC) connecting in series. The PSLC light shutter is transparent in electric field-off state; it scatters light as it switches to multi-domain structures in electric field-on states. The TiOPc film has an optically controllable impedance that manipulates the electric field on the PSLC film. The window transits into multi-transmission states according to the intensities of exposure light with an extra applied bias voltage.     

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。     

Transitions of bipolar to radial orientation of liquid crystal droplets in amphiphilic system of PDLC film

The orientation order of nanoscale droplets of thermotropic liquid crystals (LCs) suspended in polymer dispersed liquid crystal (PDLC) solutions prepared with different medias (e.g., polymers, surfactants, nonpolar materials like dyes) respond sensitively and differently via molecular interactions. Such a valuable knowledge provides basis for understanding the properties of PDLC devices. Previously, many studies have explored the droplets size, electro-optical property variations in PDLC films by varying the materials types and its compositions. However, the variations in droplet orientation order with respect to material type and composition provide a new class of study in this particular field. The current study explored the transition in droplet orientation from bipolar to radial on varying the amphiphilic block copolymer concentrations. Further, the variations in surface energies of LCs in different series of block copolymer medias were investigated by contact angle measurements.