共查询到20条相似文献,搜索用时 15 毫秒
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Corrie T. Imrie 《Liquid Crystals Today》2013,22(1):12-13
Abstract A key issue in the area of side chain liquid crystal polymers concerns the conformation of the backbone within the mesophase. In order to resolve this matter, Noirez and co-workers (Liquid Crystals, 1995, 18 129) have studied a wide range of polymers exhibiting both nematic and smectic behaviour using small angle neutron scattering. Their results combined with a survey of those in the literature reveal that if the polymer is solely nematogenic, then the backbone adopts a prolate conformation in which on average it lies along the director. By contrast, in a smectic phase the backbone adopts an oblate shape and on average lies perpendicularly with respect to the director. This arises from a microphase separation in which the backbones are distributed between the mesogenic layers. However, the backbones can cross the mesogenic layers although their ability t o do so depends on, amongst other factors, the degree of polymerization. If the polymer exhibits both nematic and smectic behaviour, then in the nematic phase the backbone adopts a slightly oblate shape resulting from smectic fluctuations. 相似文献
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Results are presented which show how defects in a nematic liquid crystal can be used to investigate material flow when external electric fields are applied. These results include measurements of the size of flow cells, which were created between the electrodes by an electric field. The electrodes, which were made of transparent conductive coated glass, were placed in a vertical position so that flow cells could be observed from the top while dynamic scattering was observed when viewing normal to the electrodes. 相似文献
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H. Hakemi 《Molecular Crystals and Liquid Crystals》2019,684(1):7-14
AbstractFollowing three decades of industrial progress and setback cycles, the Polymer Dispersed Liquid Crystal (PDLC) has currently become a growing worldwide business in the Smart Window markets. In this article, we provide a brief review of industrial evolution of PDLC film technology, its development history in Europe, the emerging products and a brief account of current global market situation. 相似文献
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L. Noirez J. P. Cotton F. Hardouin P. Keller M. Lambert F. Moussa 《Molecular Crystals and Liquid Crystals》2013,570(1)
Comb like liquid crystal polymers are polymers on each monomer is grafted a hanging liquid crystal molecule. The bulk state has the classical liquid crystal phases (nematic, smectic); what is the conformation of a chain in these phases is the problem to solve with the help of small angle neutron scattering. The values of the global sizes R || and R ‖ of a chain (in the direction parallel and perpendicular to the director) are discussed as a function of the chemical species and the temperature. Strange results are discussed in terms of segregation of labelled parts. 相似文献
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K. Mueller B. Hisgen H. Ringsdorf R. W. Lenz G. Kothe 《Molecular Crystals and Liquid Crystals》2013,570(1):167-178
Thermotropic nematic polyesters, specifically deuterated at different positions of the polymer chain are studied by multiple pulse dynamic NMR. Analysis of the NMR experiments is achieved, employing a comprehensive model, based on the stochastic Liouville equation. Computer simulations provide the orientational distributions and conformations of the polymer chains and the correlation times of the various motions. In the anisotropic melt the correlation times for chain reorientation and trans-gauche-isomerization are in the range of 0.1–10 ns. Decreasing the temperature of the solid polymer first freezes the intermolecular motions. Thus, below the glass transition only intramolecular motions such as trans-gauche isomerization and ring flips can be detected. The chain order parameter of the nematic melt is S(ZZ) = 0.85. In addition, the chains adopt a highly extended conformation, evidenced by a trans population of n(t) = 0.8 throughout the entire spacer. This microorder is retained, when the polymer is cooled below the melting point and glass transition, respectively. 相似文献
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The application of liquid crystal to display devices was first proposed by Heilmeier et al. in 1968, and a liquid crystal television (LC-TV) addressed by electron beam was made as a trial in the same year. Since then, it has taken about 15 years for practical LC-TVs to be developed. Full-color, higher resolution and greater pixel number have been attained, and presently, at least for small size LC-TVs, image quality has become very close to that of CRTs. 相似文献
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W. Renz 《Molecular Crystals and Liquid Crystals》2013,570(1):549-558
Competing nematic and smectic A phases of comb-like polymers are described by combining Maier-Saupe and McMillan type theories with the worm concept of semi-flexible polymers. There are as few material parameters as possible: main chain flexibility and phenomenological coupling constants. New qualitative predictions, the existence of critical points and re-entrant nematic phases, as well as quantitative predictions for comparison with experiments are provided. A new mechanism for thermotropic nematic biaxiality which is specific of side-chain polymeric liquid crystals is found. 相似文献
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Eight modes of the guest-host cells (GH-cells), in which types of dye, liquid crystal and their alignments are adequately combined, are surveyed, and the color contrast of each mode is calculated. Three modes among them are of positive type display, that is, colored patterns on the colorless background contrary to the initially proposed fundamental GH-cell. Another three modes are the GH-cells without polarizer, by which bright display can be obtained. Light stability of dyes are also discussed and lifetimes of various dyes are estimated by accelerated life test. As a result, it is found that diazo-and axomethine-dayes without thiazole groups as well as anthraqunone-dyes have satisfying lifetimes as long as they are used indoors. 相似文献
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T. R. Woliński K. Mileńko M. M. Tefelska K. A. Rutkowska A. W. Domański S. Ertman 《Molecular Crystals and Liquid Crystals》2014,594(1):55-62
Experimental results of polymer photonic liquid crystal fibers based on commercially available (Kiriama) PMMA and cyclo-olefin polymer (Zeonex 480R) microstructured polymer fibers infiltrated with nematic liquid crystals (2CHBT/8CHBT and PCB) are presented and thermally-tuned photonic band-gap propagation mechanism is observed. These preliminary results suggest, that polymers binding to liquid crystals much easier than silica, can offer new opportunities while using polymer-based photonic crystal fibers. 相似文献
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The trends of temperature dependence of the surface order parameter and of the anchoring strength coefficient are theoretically evaluated in the Landau-de Gennes phenomenological theory for nematic liquid crystals. The cases of planar, homeotropic and tilted alignment at a planar limiting surface are considered. It is shown that the cases with surface order parameter greater than the bulk one or smaller than this can occur in function of the phenomenological coefficients in the surface free energy expression. The anchoring strength coefficient, W, diminishes when temperature approaches the nematic-isotropic point, after passing through a maximum in most of cases. The possibility of a non-zero anchoring strength at temperatures above the transition temperature is revealed. The obtained trends of W(T) describe well a large variety of experimental results from literature. 相似文献
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Guogang Xu Jing Li Yongjie Guo Shujuan Han Jiyang Wang 《Crystal Research and Technology》2010,45(6):600-602
Crystals with a non‐centrosymmetric structure are of great interest owing to their properties such as ferroelectricity, piezoelectricity, dielectric behavior and optical properties. In this letter, Ga3PO7 crystals are grown by the top‐seeded solution growth (TSSG) method from a Li2O‐3MoO3 flux. It crystallizes in a non‐centrosymmetric trigonal crystal system with space group R3m within point group 3m. The growth defects are investigated by means of chemical etching method. The results reveal hot concentrated phosphoric acid to be a good etchant for Ga3PO7. The main defects are cracks, inclusions, dislocations and twin. In the meantime, the effective measures for reducing the defects are proposed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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D. Makow 《Molecular Crystals and Liquid Crystals》2013,570(1):347-353
Polysiloxanes with suitable side-chains form a cholesteric liquid crystal phase that can be applied to a substrate to produce a durable coating which exhibits strong colours below the glass transition temperature. The peak reflectance is almost 0.5 and a nearly 1.0 peak reflectance can be obtained using a half-wave retardation plate coated on both sides with the material and viewed from one direction against a black background. Values below 0.5 and between 0.5 and 1.0 have been also obtained using suitable solvents and alignment techniques. Many desired spectral reflectance distributions can be then obtained because of the additive color properties of such cholesteric coatings. As a result it is possible to produce a larger colour gamut than with real surface colours such as pigments and dyes. Employing commercially available material experimental work was carried out demonstrating a greatly expanded colour gamut on the chro-maticity diagram. Also it is possible to modify the spectral reflectance distribution of coloured substrates by coating them with a material having a reflectance peak at the desired band of wavelength. 相似文献
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T. Sasaki 《Molecular Crystals and Liquid Crystals》2013,570(1):281-306
The technology development of liquid crystal display started having a remarkable influence on the technology innovation of up-to-date electronic calculator. While a digital display using liquid crystal display has been developed in its earlier stage as the segment type which sets a limit of display to numeric and certain symbols, it is also spent an effort to develop the X - Y matrix type which can display alpha-numeric and moreover kana characters. As a practical application of the X - Y matrix type liquid crystal display, an alpha-numeric type scientific electronic calculator and electronic translator will be reported. Further, the present status of liquid crystal display applications and trend of R&D in other consumer and industrial electronic industries in Japan will be reported. Finally, activities in the Japanese academic circles will be presented. 相似文献
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