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Director configurations of nematic liquid crystalline droplets and corresponding configuration transitions

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Science China Chemistry 1996年第2期39卷 203-210页

作者：陆建明张红东丁建东杨玉良 Department of Macromolecular Scienoe Laboratory of Molecular Engineering of Polymers Fudan University Shanghai 200433 China

The director configurations of nematic liquid crystalline droplets and their corresponding configuration transitions were studied with Monte Carlo simulation in cubic lattices. The Lebwohl-Lasher (LL) nematogen potential was employed as the prototype of the nematic interaction between nearest-neighbor rodlike molecules. It has been found that the director configurations of nematic droplets change with the mode and strength of the interfacial interaction as well as temperature. Further description is given of the restructuring processes of spheric and elliptic nematic droplets subjected to different strengths of external fields. These results are, hence, helpful for understanding the display mechanism of polymer dispersed liquid crystal materials. The studies also demonstrate that Monte Carlo simulation based on LL model is an effective method for investigating the physics in the small systems of liquid crystal under confined geometries.

关键词： polymer dispersed liquid crystal PDLC material nematic droplet director configuration.

Existence and blow-up of the solutions to the viscous quantum magnetohydrodynamic nematic liquid crystal model

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Science China Mathematics 2019年第3期62卷 469-508页

作者： Guangwu Wang Boling Guo School of Mathematics and Information Science Guangzhou University Graduate School of China Academy of Engineering Physics Institute of Applied Physics and Computational Mathematics China Academy of Engineering Physics

In this paper, we investigate the coupled viscous quantum magnetohydrodynamic equations and nematic liquid crystal equations which describe the motion of the nematic liquid crystals under the magnetic field and the quantum effects in the two-dimensional case. We prove the existence of the global finite energy weak solutions by use of a singular pressure close to vacuum. Then we obtain the local-in-time existence of the smooth solution. In the final, the blow-up of the smooth solutions is studied. The main techniques are Faedo-Galerkin method, compactness theory, Arzela-Ascoli theorem and construction of the functional differential inequality.

关键词： viscous quantum magnetohydrodynamic equations nematic liquid crystal global weak solution singular pressure smooth solution blow-up

Magnetic-Field-Induced Weak Order in nematic Liquid Crystals Formed by Biaxial Molecules

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Chinese Physics Letters 2000年第10期17卷 749-751页

作者： ZHANG Zhi-Dong ZHANG De-Xian SUN Yu-Bao Department of Physics Hebei University of TechnologyTianjin 300130

nematic liquid crystal system of interacting biaxial particles via dispersion forces is *** molecular orienting potential form in a magnetic field is given for the first *** ordered isotropic phase is treated in the two-particle cluster *** account of the molecular biaxiality,it is found that the ratio of the lowest supercooling temperature T^(*)to the nematic-isotropic phase transition temperature TC approaches the observed value,and the validity of the mean field theory is clarified.

关键词： nematic isotropic clarified

Disclination and molecular director studies on bowlic columnar nematic phase using mosaic-like morphologydecoration method

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Science China Chemistry 2009年第7期52卷 986-999页

作者： DONG YanMing CHEN DanMei ZENG ErMan HU XiaoLan ZENG ZhiQun Department of Materials Science and Engineering College of MaterialsXiamen UniversityXiamen 361005China

Two bowlic cyclotriveratrylene CTV-1 and CTV-2, with different peripheral groups of -OCH3 and -OCH2CH3 for CTV-1 and -OCH3 and -OCH2COOCH3 for CTV-2, respectively, were synthesized by typical trimerization via a multistep sequence from vanillin. Both bowlic CTV molecules were thermotropic liquid crystals, and presented typical grainy textures of the nematic phase and homogeneous texture of the single domain nematic phase. It is of interest to observe the regular and beautiful mosaic-like morphologies after cooling from liquid crystalline phases, which appeared and vanished repeatedly in several circles of cooling and heating. The size of each mosaic was several dozens of micron. In nature, the mosaic-like morphologies are the optical pattern of cracks formed by the shrinking, due to the crystallization of frozen texture of nematic phases. By means of scanning electron microscopy, the mosaic-like morphologies were observed to consist of lamellae, and each mosaic is a rectangular multi-layer lamella, which is composed of packed single-layered lamellae. The fibrils in the diameter of about 1 μm were observed, which are the structural units of lamellae and would be the bundles of the bowlic molecular columns. The mosaic-like morphologies decorate the bowlic molecular columnar nematic phase, therefore, a novel mosaic-like morphologies decoration method was applied to reveal the director distribution of several kinds of point disclinations, such as s = +1(δ =0°and δ =90°) and s = ±1/2, and Nèel domain walls. It was shown that the bowlic molecular columnar nematic phase behaved as normal nematic phases; however, the basic structural units ordered were the bowlic molecular column or the bundles of bowlic molecular column (i.e. fibrils), but not the bowlic molecules themselves. The bowlic molecular columns acted as the rod-like molecules in a normal nematic phase. Therefore, a new term BCN (bowlic columnar nematic phase) is used to describe the anomalous nematic phase in thi

关键词： CTV bowlic molecules thermotropic liquid crystals bowlic columnar nematic phase BCN mosaic-like morphologies disclination

Laser light scattering technique for non-invasive in situ simultaneous measurements on elastic constants and viscosity coefficients of nematic liquid crystals

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Science China(Physics,Mechanics & Astronomy) 2004年第1期47卷 79-85页

作者： TU Mei HUANG Yaoxiong Institute of Biomedical Engineering Jinan University Guangzhou 510632 China Institute of Biomedical Engineering Jinan University Guangzhou 510632 China

The laser light scattering technique for non-invasivein situ simultaneous measurements on elastic constants and viscosity coefficients of nematic liquid crystals is introduced. By measuring the autocorrelation function of the scattered light from nematic liquid crystals at different scattering angles, the splay and twist elastic constantsK 11 andK 22 are obtained from the amplitudes of the autocorrelation function, and the viscosity coefficients ofη Splay andη Twist are determined using the viscoelastic ratiosK 11/η Splay andK 22 η Twist from the telaxation parameters of the two modes.

关键词： dynamic light scattering, nematic liquid crystal, elastic constants, viscosity coefficients.

Director Field in a Bipolar Configured nematic Droplet

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Journal of Electronic Science and Technology of China 2004年第2期2卷 10-14页

作者：黄子强杨文君周晓军 School of Optic-Electronic Information UESTC Chengdu 610054 China

Director field in a bipolar configured nematic droplet is analyzed numerically. Results of the calculation are expressed as the tilted angle of the director in the droplet, which balance between torque by elastic energy and the torque by external electrical field. The tilted angle is expressed as the function depending on latitude angle and relative radius r / R in the spherical droplet. The result shows that the maximum difference of the tilted angle happens at 0.87 R, where the tilted angle varies 12°C before applying external field (0 V/μm.) and after applying electrical field (0.62 V/μm). If nematic droplet would be applied as a micro lens, its focus would vary because the refractive index changes due to the change of tilted angle. According to the calculation, maximum modification of refractive index is 0.036, if E7 would be adapted as the nematic phase in the droplet.

关键词： PDLC liquid crystals nematic droplet

NONTRICRITICAL BEHAVIOR OF nematic-ISOTROPIC TRANSITION IN LIQUID CRYSTALS

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Chinese Science Bulletin 1980年第9期25卷 798-799页

作者：林磊 Institute of Physics Academia Sinica

Recently, Keyes has pointed out that oven though the nematic-isotropic (N-I) transition in liquid crystals is first order, the critical behavior of which is actually tricritical in nature. Moreover, some authors even ... 详细信息

关键词： nematic actually isotropic concluded pointed 朋曲 Cotton arrow 郝柏林王心

Molecular behaviors in thin film lubrication——Part two: Direct observation of the molecular orientation near the solid surface

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Friction 2019年第5期7卷 479-488页

作者： Ming GAO Haoyu LI Liran MA Yuan GAO Linwei MA Jianbin LUO State Key Laboratory of Tribology Tsinghua UniversityBeijing100084China School of Metallurgy Engineering Xi’an University of Architecture and TechnologyXi’an710055China School of Materials Science and Engineering Tsinghua UniversityBeijing100084China

Over the past twenty years, thin film lubrication(TFL) theory has been used to characterize the molecular behaviors in lubrication films thinner than 100 nm, effectively bridging the gap between elastohydrodynamic lubrication and boundary lubrication. Unfortunately, to date, the TFL molecular model proposed in 1996 has not been directly proven by experimental detection. Herein, a method based on surface-enhanced Raman spectroscopy was developed to show both the packing and orienting of liquid molecules in the TFL regime. By trapping liquid crystal molecules between a structured silver surface and a glass surface, molecular ordering states dominated by shear effect and surface effect were successfully distinguished. A nanosandwich structure consisting of an adsorbed layer, an ordered-molecule layer, and a fluid layer was demonstrated. Molecule imaging in TFL was achieved. Our results illustrate the molecular behaviors and lubrication mechanism in nanoconfined films and facilitate the lubrication design of nanoelectromechanical and microelectromechanical systems.

关键词： thin film lubrication molecular behaviors nematic liquid crystal surface-enhanced Raman spectroscopy lubrication theory nanosandwich structure

An investigation on a novel PDLC film's fabrication and its electro-optical properties

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Science China Chemistry 2007年第3期50卷 358-363页

作者： DING HongLiu, ZHAO Ting, CHENG YuXiao, PANG YueHong, XU He, SHI GuoYue & JIN LiTong Chemistry Department of East China Normal University, Shanghai 200062, China Chemistry Department of East China Normal University Shanghai 200062China

A polymer dispersed liquid crystal (PDLC) film that has good electro-optical properties is produced by the method of polymerized-induced phase separation. Based on the application foreground, its capability parameters, such as contrast ratio, work voltage, and visual angle, are characterized for the first time by a white light but not a fixed wavelength light. The results show the PDLC film has a low work-voltage of 20 V, more than 150° visual angle, high stability, and long lifetime. The differences between plastic and glass ITO-coated substrates of PDLC films are also studied in this paper. The plastic substrate has better property and will have a wider perspective especially in the portable, tender and folded display devices. Due to adjustable properties of film by electric field, PDLC has the potential application for display device, sensor, switch, grating, and new generation analytical apparatus.

关键词： polymer dispersed liquid crystal (PDLC) bisphenol-A epoxy resin nematic liquid crystal electro-optical properties