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941.
Mario Glanz Sebastian Dechert Herbert Schumann Dietmar Wolff Dietmar Wolff Jürgen Springer 《无机化学与普通化学杂志》2000,626(12):2467-2477
The Influence of the Coordination Sphere of Samarocenes on the Synthesis of Liquid Crystalline Polymethacrylates (C5Me5)2Sm(THF)2 ( 1 ) reacts with 1,3‐Diisopropyl‐4,5‐dimethylimidazoline‐2‐ylidene C3N2Me2iPr2 (iPr‐carben) with formation of (C5Me5)2Sm(iPr‐carben) ( 3 ). The reaction of (C5Me4Et)2Sm(THF)2 ( 2 ) with Al2Me6 in toluene yields [(C5Me4Et)2Sm(CH3)Al(CH3)3]2 ( 6 ). 3 and 6 were characterized by single crystal X‐ray structure analysis. Via living polymerization of mesogenic methacrylates with the organosamarium complexes 1 , 2 , 3 , (C5Me5)2Sm(C3H5) ( 4 ), (C5Me5)2Sm(CH3)(THF) ( 5 ), 6 , and (C5Me4Et)2SmCH(SiMe3)2 ( 7 ), liquid crystalline homo‐ and blockcopolymers were obtained with narrow molecular mass distribution indexes in high yield. Partial competitive mechanisms are observed dependend of the structure of the catalyst and the polarity of the solvents. 相似文献
942.
Dawei Guo Xiaozhen Yang Ling Yang Yufei Li Taiqi Liu Han Hong Youliang Hu 《Journal of polymer science. Part A, Polymer chemistry》2000,38(12):2232-2238
Two new silolene‐bridged metallocenes for isotactic polypropylene, racemic (1,4‐butanediyl) silylene‐bis (1‐η5‐2‐methyl‐indenyl) dichlorozironium and racemic diphenyl silylene‐bis (1‐η5‐2‐methyl‐indenyl) dichlorozironium, were designed in terms of the mechanism and concept of the activity and selectivity of metallocenes. The predictions on which the designs were based were carried out for four metallocene catalysts through molecular modeling methods such as molecular mechanics and charge equilibrium. In a comparison of the data from three of the catalysts that were successfully synthesized, the predicted orders of the activity and selectivity were consistent. This shows that classical methods such as charge equilibrium are useful in predicting the activity of catalysts. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2232–2238, 2000 相似文献
943.
Decidedly higher clearing temperatures and often also broader mesophases are exhibited by axially fluorinated cyclohexane derivatives 1 and 2 relative to their nonfluorinated analogues. A convenient method for the multigram synthesis of 1 and 2 , which represent a promising new type of liquid crystals with positive or negative dielectric anisotropy, is presented. 相似文献
944.
Myongsoo Lee Byoung-Ki Cho Heesub Kim Wang-Cheol Zin 《Angewandte Chemie (International ed. in English)》1998,37(5):638-640
The liquid crystalline behavior of compounds 1 (n = 7, 12, 15) differs significantly from that exhibited for conventional rodlike molecules. They organize into layered smectic, bicontinuous cubic or hexagonal columnar mesophases depending on the temperature or the volume fraction of coil segments. 相似文献
945.
On X-Ray Single Crystal Studies of Na2FeAlF7, Na2MIIGaF7 (MII = Ni, Zn), and Na2ZnFeF7 and the Structural Chemistry of Weberites At single crystals of the orthorhombic weberite Na2NiGaF7 (a = 716.1, b = 1021.6, c = 740.9 pm; Imma, Z = 4) and of the monoclinic variants (C2/c, Z = 16) Na2FeAlF7 (a = 1242.6, b = 727.8, c = 2420.6 pm, β = 99.99°), Na2ZnGaF7 (a = 1251.9, b = 730.3, c = 2435.3 pm, β = 99.74°) and Na2ZnFeF7 (a = 1261.0, b = 7.359, c = 2453.8 pm, β = 99.70°) complete X-ray structure determinations were performed. The results and the influence of radii on the bridge angles MII–F–MII and MII–F–MIII are discussed in connection with general features within the structural chemistry of 28 weberites. 相似文献
946.
Reversible switching from a highly rough surface to another entirely smooth surface under external stimuli is crucial for intelligent materials applied in the fields of anti-fogging,self-cleaning,oil-water separation and biotechnology.In this work,a thermal-responsive liquid crystal elastomer (LCE) surface covered with oriented micropillars is prepared via a facile two-step crosslinking method coupled with an extrusion molding program.The reversible change of topological structures of the LCE surface along with temperature is investigated by metallographic microscope,atomic force microscopy and optical contact angle measuring system.At room temperature,the LCE sample is filled with plenty of micropillars with an average length of 8.76 μm,resulting in a super-hydrophobic surface with a water contact angle (WCA) of 135°.When the temperature is increased to above the clearing point,all the micropillars disappear,the LCE surface becomes entirely fiat and presents a hydrophilic state with a WCA of 64°.The roughness-related wetting property of this microstructured LCE surface possesses good recyclability in several heating/cooling cycles.This work realizes a truly reversible transformation from a highly rough surface to an entirely smooth surface,and might promote the potential applications of this dynamic-responsive LCE surface in smart sensors and biomimetic control devices. 相似文献
947.
正交异性钢桥面板纵肋与顶板连接细节处极易产生疲劳裂纹.本文通过精细化有限元模型,分析了栓接角钢加固法和粘贴纤维增强复合材料(Fiber Reinforced Polymer, FRP)型材加固法对钢桥面板疲劳性能的影响.结果表明:采用角钢、FRP型材对顶板与纵肋连接细节的疲劳裂纹进行加固,焊缝裂纹附近热点应力峰值降幅可达56.2%和46.5%;焊缝裂纹尖端附近应力强度因子随着板件整体尺寸的增大而减小;改变板件厚度对应力强度因子结果值影响最大,最高可使其下降约80%,改变板件纵向长度和单肢长度对其有一定影响;随着裂纹的持续扩展,栓接角钢法的加固效果开始下降.建议在监测到构造细节处疲劳裂纹后应尽早加固. 相似文献
948.
Nicole Reddig Michael U. Triller Daniel Pursche Annette Rompel Bernt Krebs 《无机化学与普通化学杂志》2002,628(11):2458-2462
The tetranuclear manganese(II) complex [Mn4(ppi)6](BPh4)2 ( 2 ) (Hppi = 2‐pyridylmethyl‐2‐hydroxy phenylimine) is prepared by using the precursor complex [Mn(ppi)2]·H2O ( 1 ). Based on UV/Vis‐ and IR‐spectroscopy data in combination with mass spectrometry it has been concluded that 1 is a mononuclear neutral MnII complex, in which two ppi ligands chelate the manganese atom. Compound 2 crystallizes in the triclinic space group P1¯ (no. 2), with a = 17.500(3), b = 17.955(4), c = 19.101(4) Å, α = 113.79(3)°, β = 111.33(3)°, γ = 93.91(3)°, V = 4950(2) Å3 and Z = 2. In the tetranuclear [Mn4(ppi)6]2+ complex cation Mn(1), Mn(2), and Mn(3) are equivalently coordinated by two deprotonated Hppi ligands leading to a N4O2 donor set. The environment of the central Mn(4) is formed by coordination of three [Mn(ppi)2] fragments resulting in a phenoxo bridged star‐shaped Mn4O6 core motif. The average distance of directly adjacent manganese ions is 3.310 Å, whereas the average distance of Mn(1), Mn(2), and Mn(3) among each other is 5.732 Å. 相似文献
949.
Ronald K. Castellano Colin Nuckolls S. Holger Eichhorn Malcolm R. Wood Andrew J. Lovinger Julius Rebek Jr. 《Angewandte Chemie (International ed. in English)》1999,38(17):2603-2606
When outfitted with long alkyl chains , polycaps, capsules along a polymer chain, spontaneously organize themselves into a two-dimensional liquid crystalline phase. Further organization results from shearing or pulling the liquid crystalline samples, producing three-dimensional assemblies of micrometer-wide, infinitely long fibers (see schematic representation). 相似文献
950.
Marcus Weck Alex R. Dunn Kozo Matsumoto Geoffrey W. Coates Emil B. Lobkovsky Robert H. Grubbs 《Angewandte Chemie (International ed. in English)》1999,38(18):2741-2745
A stabilization of the liquid-crystalline mesophase and thus an enlarged temperature range of the mesogenic phase is achieved by adding perfluorotriphenylene to a chiral liquid-crystalline triphenylene. This mesophase is based on 1:1 perfluoroarene–arene interactions (see picture). In a polymer with triphenylenes as mesogens in the side chains, the addition of perfluorotriphenylene led to crystallization. 相似文献