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纤维素及其衍生物液晶研究新进展 总被引:3,自引:0,他引:3
本文全面地综述了纤维素及其衍生物溶致性液晶和热致性液晶的形成, 液晶性与大分子链结构, 以及具有胆甾型液晶相结构的纤维素衍生物复合材料等方面的最新研究进展。 相似文献
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对壬基酚聚氧乙烯醚(IgepalCO)系列表面活性剂,生成何种溶致液晶与其EO基团数n有关,而在何浓度范围内生成溶致液晶则与生成溶致液晶的最低水含量及最大水增溶量有关.EO基团数n小于10时,生成层状液晶,n大于10时则生成六角状液晶,层状液晶两亲双层内,水与表面活性剂的最低摩尔比rmin和最高摩尔比rmax随EO基团数n增加分别是非线型增加与线型增加,在IgepalCO520(n=5)中加入IgepalCO710(n=10.5),对层状液晶的生成无显著影响,在IgepalCO710中加入IgepalCO520,则对六角状液晶的生成产生显著影响,出现了六角状液晶向层状液晶的转变。 相似文献
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以羟丙基纤维素为原料,通过酯化反应合成了分子量较高的乙酰氧丙基纤维素,并用FT-IR表征了化学结构。以DSC,X-ray衍射PLM和SALS手段研究了产物的热致液晶相转变及其影响因素和溶致液晶性。实验表明,产物的乙酰基含量受合成温度和反应时间影响,其热致液晶的相转变温度和温域随乙酰基含量变化。 相似文献
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磺酸型双子表面活性剂的溶致液晶结构研究 总被引:2,自引:0,他引:2
合成了一种磺酸型双子表面活性剂6,6 -(丁基-1,4-二基双氧)双(3-壬基苯磺酸)(9BA-4-9BA), 利用偏光显微镜和X射线衍射分析仪研究了其在水溶液和乙酸乙酯溶液中的溶致液晶结构变化. 结果表明, 9BA-4-9BA在两种溶剂及其混合溶剂中均可出现溶致液晶态结构, 并且双子表面活性剂的溶致液晶相态与溶液浓度和溶剂种类密切相关. 随着浓度增加, 9BA-4-9BA水溶液溶致液晶结构由立方相经由片层立方相转变为层状液晶相, 乙酸乙酯溶液中主要以层状液晶相存在. 相似文献
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The Electro-optical properties of a composite ceramic/liquid crystal membrane, with the dispersed liquid crystals (LCs) in the high dielectric constant inorganic oxides, were investigated. The composite membranes having bicontinuous micron structure of matrices and LCs were made by the sol-gel process via the syntheses of multicomponent sols using tetra-n-butyltitanate, barium diethoxyethoxide, methyltriethoxsilane and polyethylene glycol (PEG) for phase separation. The switching behaviors of the composite films have been observed by applying AC voltages at 1 kHz. It was also confirmed that the driving voltage of the composite film depended on the composition of the inorganic oxide matrix. The composite films of high dielectric constant were driven at an electric field under 10 kV/cm, much less than that of existing PDLC. 相似文献
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Chiral columnar liquid crystals have recently appeared as a promising new type of ferroelectric materials. To date, all the columnar liquid crystals that have been reported to show ferroelectric switching consist of organic compounds. However, metal-containing liquid crystals open this field to a significant number of new structures and offer the possibility of adding to the ferroelectric behavior other properties inherent to the presence of metals in the structure, such as magnetism, as well as the use of new methods of characterization (EPR, synchrotron radiation, etc.). The potential of columnar metal-containing liquid crystals as ferroelectric materials has been demonstrated even though only a few organic columnar ferroelectric liquid crystals have been described. As a first approach to this type of material, this concepts article describes the results obtained with chiral metal beta-diketonates that show ferroelectric switching in the columnar mesophase. It has been shown that these materials have a helical columnar arrangement in the mesomorphic state, and a chiral superstructure has been proposed from circular dichroism studies. This type of supramolecular structure plays a fundamental role in the ferroelectric properties of these compounds. The discussion is mainly focused on the strategy employed for the molecular design, and on the interpretation of the mesophase structure and the electrooptic effect. The use of a diverse range of techniques, both those commonly used in the field of liquid crystals and those that are more specific will be highlighted, and the principles of these specific techniques are summarized together with a justification of their applicability to this study. 相似文献
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《Solid State Sciences》2000,2(3):313-334
The latest developments in inorganic membranes are closely related to recent advances in solid state science. Sol–gel processing, plasma-enhanced chemical vapor deposition and hydrothermal synthesis are methods that can be used for inorganic membrane preparation. Innovative concepts from material science (templating effect, nanophase materials, growing of continuous zeolite layers, hybrid organic–inorganic materials) have been applied by our group to the preparation of inorganic membrane materials. Sol–gel-derived nanophase ceramic membranes are presented with current applications in nanofiltration and catalytic membrane reactors. Silica membranes with an ordered porosity, due to liquid crystal phase templating effect, are described with potential application in pervaporation. Defect-free and thermally stable zeolite membranes can be obtained through an original synthesis method, in which zeolite crystals are grown inside the pores of a support. Hybrid organic–inorganic materials with permselective properties for gas separation and facilitated transport of solutes in liquid media, have been successfully adapted to membrane applications. Potential membrane developments offered by CVD deposition techniques are also illustrated through several examples related to the preparation of purely inorganic and hybrid organic–inorganic membrane materials. 相似文献
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Nobuyuki Tamaoki Takashi Kamei 《Journal of Photochemistry and Photobiology, C: Photochemistry Reviews》2010,11(2-3):47-61
Photochromic reactions in liquid crystals induce re-alignments of the host molecules, accompanied by changes in the optical properties and various other properties of the materials. Since the first report by Sackmann in 1971, various combinations of photochromic compounds and liquid crystals have been studied to elicit the reversible photo-regulated changes of various properties. In this report we review the advances of this field during the past 5 years, which include the creation of mechanical functions, the regulation of novel optical properties, cholesteric liquid crystals doped with azobenzene compounds in high concentrations, the regulation of ferroelectric liquid crystals, the induction of chirality by circularly polarized light, photoresponsive chiral dopants, and the photo-regulation of the oscillation wavelength of mirrorless lasers. 相似文献
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V. N. Chikanov 《Russian Journal of Inorganic Chemistry》2014,59(11):1343-1345
The data on the formation of liquid crystals in inorganic substances, in particular, in the chloride system KCl-TaCl5, were presented for the first time. The obtained experimental results of differential thermal and visual polythermal analyses and electrical conductivity measurements indicated the presence of liquid crystals in this system. Important factors of the formation of liquid crystals are the existence of a congruently melting substance in the system and the existence of polymorphic modifications of this substance. 相似文献
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Domain instabilities have been observed in the planar texture of smectic A liquid crystals. The influence of the material parameters and of the applied field on the characteristics of this phenomena have been studied. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(32):9674-9678
The design of efficient noncentrosymmetric materials remains the ultimate goal in the field of organic second‐order nonlinear optics. Unlike inorganic crystals currently used in second‐order nonlinear optical applications, organic materials are an attractive alternative owing to their fast electro‐optical response and processability, but their alignment into noncentrosymmetric film remains challenging. Here, symmetry breaking by judicious functionalization of 3D organic octupoles allows the emergence of multifunctional liquid crystalline chromophores which can easily be processed into large, flexible, thin, and self‐oriented films with second harmonic generation responses competitive to the prototypical inorganic KH2PO4 crystals. The liquid‐crystalline nature of these chiral organic films also permits the modulation of the nonlinear optical properties owing to the sensitivity of the supramolecular organization to temperature, leading to the development of tunable macroscopic materials. 相似文献
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本文报道用聚乙烯咔唑-2,4,7三硝基芴酮电荷转移复合物作光导层,与向列型及胆甾向列型混合液晶组成的夹心池结构制成的扭曲场效应、相变存储效应及动态存储效应三种直流透射式光阀及其性能的研究结果。制得的光阀均有明显开关效应。此外,还详细研究了扭曲场效应液晶光阀的阈值电压、对比度及上升时间与写入光功率的依赖关系。用白光写入,He-Ne激光读出,在扭曲场效应光阀上可实现非相干光-相干光转换,得到图象。用MTF法测得的光阀分辨率为34lps/mm。 相似文献
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《Liquid crystals》1998,24(1):127-130
Defects are a universal feature in systems of broken equally well in liquid crystals and cosmological theories in both systems are reviewed. It is reported crystals to check theories on the defect evolution of the early universe and how in this way they have contributed considerably to the insight liquid crystals. symmetry. They occur for example field theories. The basic facts of defect how cosmologists have used liquid into defect creation and dynamics in 相似文献
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The game of molecular engineering of liquid crystalline systems via a combination of molecular architecture and functionalization of mesogens has opened interesting perspectives in the field of liquid crystals. Here we report on the synthesis and characterization of star-like heptameric triphenylenes. The discotic subunits in these molecules have been arranged in a hexagonal fashion around a central discotic core, thus leading to a new type of molecular arrangement for discotic liquid crystals. These oligomers do not crystallize and combine a well-defined structure with a discotic polymer-like processing. 相似文献