Synthesis and helical twisting property of polymerizable chiral dopant with temperature-dependent solubility in liquid crystal

In this study, right-handed dicinnamate isosorbide was synthesized via the esterification reaction betweefi optically active isosorbide and cinnamate. The chiral dopant was characterized by FT-IR, ^1H NMR, elemental analysis, SEM, UV absorption spectrum. After dissolving in a nematic liquid crystal mixture, the chiral dopant exhibited a temperature-dependent solubility in the chiral nematic liquid crystal mixture. Meanwhile, a relatively high value of helical twisting power of the polymerizable chiral dopant was determined. The results show that the chiral dopant has great potential in achieving a polymer stabilized chiral nematic liquid crystal film with a broad-band selective reflection. C 2009 Huai Yang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Controllable CPL response driven by achiral UV-photosensitive dichroic dye through cholesteric liquid crystals

Versatile stimuli-responsive circularly polarized luminescent(CPL)materials have potential applications in information storage,security encryption,and intelligent displays.In this study,the Z/E isomerization of ultraviolet(UV)-photosensitive achiralα-cyanostilbene derivative was used as an achiral dichroic dye(Switch)to drive the controllable CPL-active response in cholesteric liquid crystals(CLCs).Under irradiation by 365 nm UV light,the resulting CLCs-Z-Switch underwent a Z-to-E configuration isomerization as CLCs-E-Switch,accompanied by a decrease in its dichroic order parameter(SFvalue)from 0.15to 0.07.Although the quantum yield(QY)of CLCs-E-Switch increased from 8.1%(CLCs-Z-Switch)to 16.8%,the corresponding glumvalues of CPL emission decreased from+0.55/-0.57 to+0.37/-0.39 due to a decrease in the order of helical arrangement of E-Switch in E7 media.This study enables photosensitive CLCs-Switch to be applied for optical information storage devices.

Optical properties of stacked liquid crystal superstructures with opposite chirality [Invited]

Cholesteric liquid crystal (CLC) has been widely used in flat optical elements due to the Pancharatnam–Berry(PB) phase modulation. In order to achieve PB phase modulation for both circular polarizations, it is natural to come up with stacking CLCs with opposite chirality. Here, various optical properties of diverse CLC stacking structures are systematically investigated by numerical calculations. With the thickness of the CLC sublayers becoming smaller, the reflection bandgap splits into three main parts, and the rotatory dispersion gradually becomes negligible. Vector beams provide a more intuitive verification. These results provide theoretical guidance for future studies on stacked chiral anisotropic media.

Dynamic Control of Multiple Optical Patterns of Cholesteric Liquid Crystal Microdroplets by Light-Driven Molecular Motors

The key to high-level encryption and anti-counterfeiting techniques is the storage of multiple levels of distinct information that can be individually and precisely addressed by certain stimuli.This continues to be a formidable challenge as the concealed images or codes must be read with fast response and high resolution without cross-talk to the first layer of information.Here,we report a non-fluorescencebased strategy to establish responsive encryption labels taking advantage of solely tuning multiple optical patterns of cholesteric liquid crystal(CLC)microdroplets doped with light-driven molecular motors.The photo-triggered unidirectional rotation of the motor induced not only changes in the helical twist power value but the opposite helical orientation of the superstructure in CLCs as well,resulting in changes in both the structural color and the selective reflection of circularly polar light.The designed labels,which featured highly selective addressability of dual-level distinct information,good reversibility,and viewing angle-independence,were applied to build devices for daily practical use,demonstrating great potential in anti-counterfeiting technology and provide a versatile platform for enhanced data protection and encryption of authentic information.

胆甾相液晶色彩调制的研究性实验设计

胆甾相液晶的螺距能随材料配比、温度、外加电场等发生改变,进而对外界光进行调制。针对胆甾相液晶温致变色等现象,设计了研究性实验“胆甾相液晶色彩调制的研究性实验设计”,探究了胆甾相液晶材料的清亮点、织构、螺距和选择性反射随手性剂浓度和温度的变化规律。该实验流程完整,涉及材料配制、光学测量和性能检测,并将理论与实际应用相结合,有助于激发学生对温致变色材料的研究兴趣,培养学生创新性实验方案设计能力。

Smart chiral liquid crystal elastomers:Design,properties and application

Smart chiral liquid crystal elastomers are a class of soft photonic crystals with periodic nanostructures.There are two kinds of chiral liquid crystal elastomers with structural colors:cholesteric liquid crystal elastomers with a one-dimensional helical nanostructure and blue-phase liquid crystal elastomers with a three-dimensional photonic crystal nanostructure.The self-assembled nanostructure of chiral liquid crystal elastomers can be dynamically controlled under external stimulation,and the reflected color can be adjusted throughout the visible light range.Along with the development of innovative material systems and cutting-edge manufacturing technologies,researchers have proposed diverse strategies to design and synthesize chiral liquid crystal elastomers and have thoroughly investigated their properties and potential applications.Here,we provide a systematic review of the progress in the design and fabrication of smart chiral liquid crystal elastomers,focusing on the cholesteric liquid crystal elastomers via surface-enforced alignment,bar coating,3D printing,anisotropic deswelling methods as well as the three-dimensional selfassembly of blue-phase liquid crystal elastomers without additional alignment.Smart chiral liquid crystal elastomers are able to respond quickly to external stimuli and have a wide range of applications in areas such as adaptive optics,color-changing camouflage,soft robotics,and information encryption.This review concludes with a perspective on the opportunities and challenges for the future development of smart chiral liquid crystal elastomers.

Influence of terminal alkyl chain length on helical twisting property of chiral 1,2-propanediol derivatives

In this study, a novel series of chiral 1,2-propanediol derivatives with different terminal alkyl chain length were synthesized and characterized by FT-IR, ^1H NMR and DSC. After doped into a nematic liquid crystal host, all the chiral dopants induced chiral nematic liquid crystals exhibiting a helix inversion with temperature variation. The results indicate that terminal alkyl chain length has a prominent influence on helical twisting property of the chiral dopants. With increasing the terminal alkyl chain length, the molecular twisting power increases, the helix inversion temperatures varies slightly while the phase transition temperature decreases. An odd-even effect may exist in the molecular twisting power of the chirai dopants.

柱筒中掺杂手性剂向列相液晶的介电及挠曲电性能

在电场作用下,同心圆柱筒中的介电作用及挠曲电作用具有与平面液晶盒中不同的性质。本文在轴向强锚定边界条件下,对柱筒内添加手性剂的向列相液晶5CB施加径向电场,分别研究了介电效应和挠曲电效应对指向矢分布的影响。基于液晶连续体弹性理论和有限差分迭代方法,计算了体平衡态方程。通过数值计算发现,挠曲电系数e1、e3具有不同的取向作用。本文的模拟结果为电场作用下柱筒内手性向列相液晶指向矢结构的预测提供了更全面的理论分析,对液晶挠曲电系数的测量也具有一定的指导意义。

A New Chirality Invertible Photoswitch:Light-Driven Axially Chiral Hydrazone Enabling Dynamic Handedness Inversion of Self-Organized Helical Superstructure

Inspired by nature,dynamic self-organized helical superstructures are becoming attractive as building blocks in soft photonic crystals and advanced chiroptical devices.Herein,a chirality invertible hydrazone photoswitch,possessing high helical twisting power(HTP)was judiciously designed and synthesized.Due to the photoinduced configuration changes of the hydrazone photoswitch,it displayed superior thermal stability and strikingly reversible HTP changes.By incorporating a novel chiral hydrazone(CH)into the liquid crystal(LC)host,a handedness invertible cholesteric liquid crystal(CLC)helical superstructure with high thermal stability and light-modulated photonic bandgap was prepared.We inferred that the mechanism of chirality inversion of the novel CH photoswitch derived from changes in the dihedral angle between the two naphthalene rings induced by hydrazone isomerization.Therefore,the influence of chemical structures on its photoresponsiveness was explored.Finally,the potential applications of this advanced light-driven CLC in soft photonic crystals,showing erasable and rewritable colorful patterns and chiroptical templates to induce handedness invertible circularly polarized luminescence were illustrated.

显示用胆甾相液晶材料发展现状

介绍了胆甾相液晶显示性能和对液晶材料的要求,分析了近几年高双折射率液晶化合物和手性掺加剂及其胆甾相液晶材料的应用与发展情况,初步阐明了分子结构与液晶性能及其手性掺加剂的HTP值之间的依存关系,为开发新型液晶化合物、手性化合物和胆甾相液晶材料提供了线索。

一种手征向列相液晶的螺旋行为研究

以1,2-丙二醇为不对称中心制备了一系列手性掺杂物,与4-烷基联苯氰类向列相液晶混合配制成手征向列相液晶。通过对手征向列相液晶螺距及螺距温度依赖性的研究,发现手性掺杂物分子的末端烷基链的增长对其螺旋扭曲力有一定的影响;而手性碳原子上取代基的改变,对手性分子的螺旋扭曲力和温度依赖性有强烈的影响。

具有宽波反射特性的手征向列相液晶的研究进展

简要说明了手征向列相液晶的形成方式、分子排列特点和光学性质,详细介绍了具有宽波反射特性的手征向列相液晶在国内外的研究进展情况,概括了特殊的多螺距分布结构的形成机理,并展望了其应用前景及发展方向。

纳米粒网络对于手性液晶反射光谱的展宽效应

依据分子呈螺旋型排列的介质的电磁场解计算了给定厚度的手性液晶的光谱反射率与其双折射的关系,依据布拉格反射的干涉条件计算了斜入射光的布拉格反射光谱的蓝移。从中发现:(1)若液晶的双折射大于0.2,液晶层的厚度达到3μm就可使反射率高于90%;(2)若要以液晶的平面态实现整个光谱范围的布拉格反射,液晶的双折射应当达到0.6以上;(3)入射角达到60°时手性液晶的反射光谱蓝移可达到100nm。然而,商品手性液晶的双折射只有0.2左右,为了将这样的手性液晶用于在整个可见光谱反射的显示器件,就需要在液晶中引入聚合物网络,并在玻璃基片表面实现聚合物的凹凸结构。网络的作用是要在液晶层中建立随机分布的分子锚定机制,使手性液晶的螺距随位置而变化,从而展宽其布拉格反射谱。基片表面的凹凸结构用于诱导液晶螺旋轴的斜向随机分布,以利用倾斜螺旋结构布拉格反射的蓝移现象,进一步展宽布拉格反射谱。实验证明,在液晶中引入聚合物网络和表面的凹凸结构以后,手性液晶的布拉格反射区间由原来的80nm增加到120nm以上,对比度达到4∶1左右。

含葡萄糖基元的胆甾型液晶聚合物的合成与表征

把手性单体1-O-（十一烯）-β-D-四乙酰葡萄糖苷（M1）和液晶单体4-烯丙氧基苯甲酸胆甾醇酯（M2）接枝到聚甲基含氢硅氧烷上，手性单体的摩尔分数从0至30％，得到系列液晶聚合物．通过红外光谱（IR）、核磁共振谱（^1HNMR）、旋光分析、差示扫描量热法（DSC）、偏光显微分析法（POM）、热失重分析法（TGA）、X射线分析等手段研究了手性单体对侧链胆甾型液晶聚合物性能的影响．结果表明P1～P7都有液晶性且为胆甾型液晶聚合物，系列液晶聚合物的tg和ti随手性单体含量的增加而降低，P1～P7具有较宽的液晶相范围，热稳定性较高，质量损失5％时的热失重温度均在300℃左右．

苯基嘧啶类铁电液晶及手性掺杂剂的研究进展

自从Clark和Lagerwall提出表面双稳铁电液晶显示原理后,铁电液晶材料在显示领域中的应用一直是国内外研究的热点课题。本文介绍了近年来新型苯基嘧啶类铁电液晶及手性掺杂剂的研究进展,重点讨论了不同结构的手性中心和末端链对其自发极化率、响应时间和相变温度的影响。

含供吸电子的手性液晶聚合物的合成与性能

将有供电子基团的手性单体M1和含吸电子基团的单体M2接枝到聚甲基含氢硅氧烷上,得到系列手性液晶聚合物,其中,手性单体的摩尔分数为0～50%.通过红外光谱(IR)、核磁共振谱(1HNMR)、差示扫描量热法(DSC)、偏光显微分析法(POM)、热失重分析法(TGA)、X射线分析等手段研究了手性单体的含量及供吸基团对侧链胆甾型液晶聚合物性能的影响.结果表明P1～P8都有液晶性且为胆甾型液晶聚合物,系列液晶聚合物的tg随手性单体含量的增加而增加,ti随手性单体含量的增加而降低,P1～P8具有较宽的液晶相范围,热稳定性较高,质量损失5%时的热失重温度均在300℃左右.

手征性向列相液晶复合体系的研究

以(+)-2-甲基丁醇为不对称中心制备了单手性中心与双手性中心两个系列的液晶用手性掺杂物,分别将其与4-烷基联苯氰类向列相液晶混合。通过对单手性中心掺杂物/向列相液晶复合体系的研究,发现了手性中心的旋转自由度对其螺旋扭曲力的影响规律;进一步制备了双手性中心掺杂物,并对双手性中心掺杂物/向列相液晶复合体系的螺旋扭曲力及其螺距的温度依赖性进行研究,发现两个手性中心之间的链接方式对其螺旋扭曲力的温度依赖性有强烈的影响。

平板显示中的双稳态技术:现状与进展(一)

介绍双稳态显示器件的原理、开展双稳态显示技术的意义和基本思路。在此基础上简要介绍现有比较成熟的几种双稳态显示器件的基本原理、基本特性、研究进展和存在的问题,包括以液晶材料为核心的双稳态器件、基于光干涉与机械双稳态机构的iMod显示器件、基于电泳现象的零电场双稳态E-ink显示器件。由于双稳态发展历史已经很久,本篇综述的宗旨不在于介绍最新的发展状况,而在于为提供双稳态显示器件较为完整的创造思想和方法。在液晶显示单元双稳态化的基础上,作者提出OLED阵列、FED阵列的双稳态结构的原理与技术途径。提出通过现有技术的组合,实现显示器件双稳态化的大屏幕显示器件的发展思路。

平板显示中的双稳态技术:现状与进展(二)

介绍双稳态显示器件的原理,推广双稳态显示技术的意义和基本思路。在此基础上简要介绍现有比较成熟的几种双稳态显示器件的基本原理、基本特性、研究进展和存在的问题,包括以液晶材料为核心的双稳态器件、基于光干涉与机械双稳态机构的iMod显示器件、基于电泳现象的零电场双稳态E-ink显示器件。由于双稳态发展历史已经很长,本篇综述的宗旨不在于介绍最新的发展状况,而在于为双稳态显示器件提供较为完整的创造思想和方法。在液晶显示单元双稳态化的基础上,作者提出OLED阵列、FED阵列的双稳态结构的原理与技术途径。提出通过现有技术的组合,实现显示器件双稳态化的大屏幕显示器件的发展思路。