Smart beam via electrically addressing the dye-doped and polymer-stabilized cholesteric liquid crystals

Smart beams play a vital role in modern intelligent vehicles and have recently attracted significant attention.A spatial light modulator with high optical efficiency,low cost,and compact size is crucial for designing smart beams.Here,we mix cholesteric liquid crystals with dichroic black dye and a monomer.After UV polymerization,the sample exhibits a low driving voltage of 26 V,a high transmittance of over 70%,and an On-off ratio over 280,thanks to the joint contribution of both the absorption and the scattering effect.A smart beam device is demonstrated by electrically addressing the dye-doped and polymer-stabilized cholesteric liquid crystal with pixelated electrodes.Light patterns with arbitrary designs are projected dynamically.The switching time reaches several tens of milliseconds.This strategy brings new designs to intelligent vehicles and may also inspire applications in public information displays,advertising,and even AR/VR displays.

Enhanced circularly polarized luminescence emission promoted by achiral dichroic oligomers of F8BT in cholesteric liquid crystal

In the exploration of circularly polarized luminescence(CPL)materials,doping cholesteric liquid crystals(CLCs)with achiral dyes is a common strategy.Conjugated polymers are favored as achiral dyes for their superior luminescent properties.In this study,a series of oligomers(M1-M3)and the conjugated polymer F8BT were synthesized to systematically assess the impact of the length of the conjugated backbone on CPL signals of CLCs doped with conjugated polymers.As the length rose from M1 to M3,CPL intensity concurrently increased(|g_(lum)|increased from 0.35 to 0.84),attributable to enhanced dichroism(order parameter,SFincreased from 0.20 to 0.56).In contrast,F8BT polymer resulted in diminished CPL intensity(|g_(lum)|=0.64)due to the reduced compatibility.Achieving a balance between dichroism and compatibility is crucial for optimizing CPL in conjugated polymer-doped CLCs.The guiding principle established here may have broad applicability in other CPL assemblies,offering a strategic avenue to engineer highperformance CPL materials with conjugated polymer.

Electro-optical properties cholesteric liquid of polymer stabilized crystal film＊

Liquid crystals （LCs） and polymers are extensively used in various electro-optical applications. In this paper, normal mode polymer stabilized cholesteric LC film is prepared and studied. The effects of chiral dopant and monomer concentrations on the electro-optical properties, such as contrast ratio, driving voltage, hysteresis width and response time, are investigated. The reasons of electro-optical properties influenced by the concentrations of the materials are discussed. Through the proper material recipe, the electro-optical properties of polymer stabilized cholesteric LC film can be optimized.

Fixation for the helical structure of a glassy cholesteric liquid crystal reflective film

The planar texture of glassy cholesteric siloxane cyclic side-chain liquid crystals was fixed by quenching initially. Then the polymer network formed by the optically active polymerizable monomers imposed additional constraints on the motion of chain segments of the glassy liquid crystal and then further stabilized the molecule arrangement. A cholesteric liquid crystal film with stable optical properties was developed by this method.

Research progress of cholesteric liquid crystals with broadband reflection characteristics in application of intelligent optical modulation materials

Cholesteric liquid crystals（CLCs） have recently sparked an enormous amount of interest in the development of soft matter materials due to their unique ability to self-organize into a helical supra-molecular architecture and their excellent selective reflection of light based on the Bragg relationship.Nowadays,by the virtue of building the self-organized nanostructures with pitch gradient or non-uniform pitch distribution,extensive work has already been performed to obtain CLC films with a broad reflection band.Based on authors＇ many years＇ research experience,this critical review systematically summarizes the physical and optical background of the CLCs with broadband reflection characteristics,methods to obtain broadband reflection of CLCs,as well as the application in the field of intelligent optical modulation materials.Combined with the research status and the advantages in the field,the important basic and applied scientific problems in the research direction are also introduced.

SYNTHESIS OF AZA-CROWN-ETHER CHOLESTERIC LIQUID CRYSTALS

Five aza-crown-ethers were synthesized and four of them shown to have cholesteric liquid crystalline properties. Their properties relevant to cholesteric liquid crystal were determined by DSC and the textures. The type of cholesteric mesomorphic azacrown ether have not been reported so far.

Tunable Optical Filters Based on Different Configurations with Cholesteric Liquid Crystals

Optical filters with different configurations based on cholesteric liquid crystals （CLCs） are designed. The central wavelength from CLCs can be tuned by the electric field or temperature. For the electric field tuning, the ITO is designed with circular patterns, which can make the tunable range 18 nm. For the temperature tuning, two-layer- CLC configurations are used. The experimental results indicate that a deepened or broadened bandgap from the CLC can be achieved by different handedness or concentrations of chiral dopants. The spectrum study is carried out.

Effect of Ferroelectric Nanopowder on Electrical and Acoustical Properties of Cholesteric Liquid Crystal

The composite materials based on nanopowder dispersed liquid crystals are important both from fundamental research and device applications due to their unique properties such as improvement in various properties like electrical,optical,thermal,energy storage and spontaneous polarization etc.The proper selection of nanoparticle and its size which to be dispersed in particular liquid crystals is very important for a particular application.In the present study,a ferroelectric nanopowder of Barium Titanate(BaTiO3)was dispersed in cholesteric liquid crystal and the same was confirmed by Fourier Transform Infrared(FTIR)Spectroscopy.The various acoustical properties like ultrasonic velocity,density,Adiabatic Compressibility,Rao Constant,Wada Constant and Acoustic Impedance were investigated by ultrasonic interferometer at room temperature at fixed frequency.The dielectric constant was determined by Precision Impedance Analyzer.In addition to these investigations,particle size and surface area were also measured.Our investigation shows enhanced in dielectric and acoustical properties which may be useful for device applications extensively in microelectronics,low cost-photovoltaic devices,and custom-shaped containers possibly applied as a coating.

Thermo-Chromic Response of Polymer Stabilized Cholesteric Liquid Crystal for Thermal Imaging

Cholesteric liquid crystal(Ch-LC)exhibits many remarkable optical properties due to formation of a macroscopic helical structure.A low amount of monomer(5wt.%)is dispersed into cholesteric liquid crystal and get polymerized under UV radiations to form polymer stabilized cholesteric texture(PSCT).The thermo-chromic response made this device suitable for the developing applications in thermal imaging.Temperature based measurements of PSCT exploits the key property of some polymer stabilized cholesteric liquid crystals(PSCLC)to reflect definite colors at specific temperatures.The selective color of PSCT texture shifts with raise in temperature from 30oC to 85oC,which can be utilized in thermal imaging applications.

Light-triggered fluorochromic cholesteric liquid crystal elastomer with hydrogen-bonded fluorescent switch: dualmodal-switchable circularly polarized luminescence

Solid materials with dynamically tunable circularly polarized luminescence(CPL) feature higher security levels and devicefriendly characteristics, showing great superiority in the field of information technology and anti-counterfeiting. To address the limited photoisomerization of fluorescent photoswitch in CPL-active solid materials, here a cholesteric liquid crystal elastomer(CLCE) containing a hydrogen-bonded(H-bonded) polymerizable fluorescent switch AHBA-PSD is prepared. Owing to the good flexibility and low glass-transition temperature of CLCE, AHBA-PSD shows a fast and fully reversible photocyclization/cycloreversion with fluorochromic behavior in CLCE. Further, by controlling the spectral overlapping area between the emission and reflection bands, the CLCE exhibits a strong CPL with a g_(lum) value of up to 0.76 accompanied by a reversible phototunable CPL signal. Meanwhile, the H-bond helps to stabilize the mechanical property, and the force-induced switching-off of CPL signal could be achieved due to the destroyed helical structures by external force. Finally, an automatically-recognized identification card with abundant chiroptical information is demonstrated.

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.

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.

Reinvestigation of liquid crystalline property of dimesogenic compound consisting of cholesterol and cyanobiphenyl

The dimesogenic compound consisting of cholesterol and cyanobiphenyl mesogens interlinked by ω-oxyalkanoyl spacer was synthesized. The mesomorphic properties were investigated by differential scanning calorimetry （DSC）, polarizing optical microscopy （POM）, and X-ray diffraction （XRD）. The experimental results indicated that this compound exhibited mesophase over a much wider temperature range and a new mesophase blue phase （BP）. Focal conic domains （FCDs） and droplets texture to the smectic A phase （SA）, oily streaks typical to the chiral nematic （N＊） phase were found in the liquid crystalline state, respectively. Besides, it exhibited a smectic layer spacing about 1.0 time to the length of the molecule, which indicated a monolayer type of SA ordering. 2009 Hal Quan Zhang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Synthesis and Characterization of a Novel Liquid Crystalline Chitin Quaternary Ammonium Chitosan Salt

N -Butyl chitosan(NBCS) derivatives were prepared by introducing butyl groups into the amine groups of chitosan via Schiff base intermediates. The quaternization of NBCS was carried out by using ethyl iodide to produce water-soluble cationic polyelectrolytes. The degree of the substitution of the products was measured by means of the electron spectroscopy for a successful chemical analysis. The quaternary ammonium chitosan salt(QACS) was proved to be a novel cholesteric liquid crystalline chitin, by means of the polarized optical microscopy and the circular dichroism spectropolarimetry. The critical mass fraction of the QACS/formic acid solution forming a lyotropic liquid crystal phase was 50%, which was almost the same as that of the NBCS/formic acid solution, but much higher than that of the chitosan in the same solvent.

SYNTHESIS OF DIACETYLENE-CONTAINING COPOLYESTERS AND THEIR DFFECT ON ELECTRO-OPTICAL PROPERTIES OF LIQUID CRYSTALS

Some diacetylene-containing copolyesters with different ratios of dipropargyl 1,10-decanate anddipropargyl terephthalate were synthesized. Properties of these copolymers were characterized by differentialscanning calorimetry and polarizing optical microscopy. The copolymer could be cross-linked easily by UVirradiation in a liquid crystal matrix without adding any photoinitiator. The preliminary studies showed thatthe diacetylene-containing polymer network can assist liquid crystal molecules to align with the externalelectric field, thus reducing the response time of display devices.

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。

胆甾相液晶微球光子禁带的动态调控及其应用

胆甾相液晶微球是空间结构高度对称的三维光子晶体,能够全方位地选择性反射特定波长的圆偏振光,具有无角度依赖性的光子禁带,作为一种新兴的光学材料在全向激光器、反射式显示和微传感器等领域展现出广阔的应用前景。近年来,毛细管微流控技术的蓬勃发展为连续、可控、高通量地制备结构复杂且分子规则取向的单分散胆甾相液晶微球提供了强有力的支持。本综述重点关注利用毛细管微流控技术制备胆甾相液晶微球的相关研究工作,首先分析了毛细管微流控装置在设计微球结构中的决定性作用,阐明了溶液体系的选择与液晶分子取向间的关系以及边界效应对微球尺寸的影响;随后,从胆甾相液晶微球的光学特性切入,介绍了利用温度、溶剂和光等外界刺激调控螺旋结构自组装的原理和策略以及微球之间独有的“光子交叉通讯”现象;最后,总结了现阶段胆甾相液晶微球的潜在应用方向并讨论了该材料体系未来面临的挑战。

胆甾相液晶图案的动态调控与应用

自然界光子晶体图案为生物的生存提供了独特的功能,例如变色龙使其皮肤图案颜色适应环境以进行伪装保护,头足类动物(鱿鱼、墨鱼、章鱼等)能够产生宽波长范围的结构颜色和光学图案以利于物种间的信息交流。受自然界光学图案的特殊功能启发,胆甾相液晶的图案得以开发,并在数据存贮、传感器、柔性智能器件等方面展示了潜在应用。本文综述了胆甾相液晶图案的外场刺激响应性、功能演变及其应用。首先,总结了胆甾相液晶图案的外场刺激响应性,包括光、电、热、机械力和溶剂。其次,介绍了胆甾相液晶图案的各种应用,如具有加密和解密功能的存贮器件、信息安全防伪设备、柔性可穿戴传感器和圆偏振发光系统等。最后,介绍了胆甾相液晶图案的前景和挑战。本文为构建基于胆甾相液晶图案的新型功能材料提供了基础。

密封沉积处理对纤维素纳米晶体薄膜光学特性的调控

纤维素纳米晶体(Cellulose nanocrystal,CNC)在特定浓度下可自组装排列,赋予体系独特的光学性能。为阐明CNC薄膜形成过程中CNC自组装行为机制,本文通过分析CNC薄膜在宏观颜色、紫外可见光谱、偏振光学、微观形貌以及晶体结构等方面的变化,探究了密封沉积时间和CNC浓度对自然蒸发干燥薄膜内部胆甾相液晶形成与排列的影响。结果表明,当密封沉积时间延长至48 h后,CNC薄膜的结构色显色范围、胆甾相结构的长程有序性均得到明显提升。随着浓度的升高,CNC颗粒间距减小,相邻颗粒间扭转角增大,螺距被压缩,从480 nm减小至344 nm。此外,密封沉积处理对高浓度CNC悬浮液形成长程有序性胆甾相结构具有明显优势。本研究结果表明,延长密封沉积时间和提高CNC浓度可以提高薄膜中长程有序性的提高,并促进胆甾相结构域的形成。这进一步完善了CNC基智能包装材料制备的科学基础,对于新型可视化食品包装和检测材料的开发具有积极作用。