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971.
Perfluorooctanoyl modified poly(vinyl alcohol)s (FPVA) were prepared by means of substituting a small amountof hydroxyl groups on the backbone of poly(vinyl alcohol), for which the initial degree of polymerization is equal to 1750.The substitution extent, defined by the number of substituting units in a chain, for the four FPVA samples was in the range of0.5-5 perfluorooctanoyl groups per chain. The FPVA samples with the highest substitution extent still had good solubility inwater. It was shown by experimental measurement at 30.0±0.1℃ that the surface tension of the aqueous solution of thehighest substituted FPVA decreased to 16.6 mN/In at a higher concentration, e.g about 0.1 g/mL. Obviously,macromolecules of FPVA exhibit a very strong tendency to adsorb at the air-water interface, because the hydrophobicperfluorooctanoyl groups in FPVA have a very high surface activity as they are in small molecular fluorinated surfactants.The chain conformation of such a model polymer adsorbed on the air-water interface was also discussed. 相似文献
972.
Wang Zhong-Ming Lin Hua-Kuan Zhou Zhi-Fen Zhu Shou-Rong Chen Yun-Ti Murmann R. Kent 《Transition Metal Chemistry》2000,25(5):562-567
The kinetics of the reaction of CH2O with a quasi-aromatic metal complex (1,1,2,8,9,9-hexamethyl-4,6-dioxa-5-hydro-3,7,10,14-tetraazacyclotetradecane-2,7,10,12-tetraene)copper(II), [Cu(PnAO)-6H]0 (AH), have been studied spectrophotometrically under neutral conditions in 1/3(v/v) MeOH–H2O. The Cu, 2N, 3C quasi-aromatic heterocyclic ring in AH is highly reactive towards CH2O at the central-aromatic-carbon atom, C(12) and the following reaction mechanism is proposed.
The compounds AH, A—CH2OH and A—CH2—A were isolated and identified by i.r spectroscopy and by elemental analysis. The kinetic data supported the proposed reaction sequence. All reactions were second order overall. The rate constants and corresponding activation parameters for every step were obtained and are discussed. 相似文献
973.
本文报道了用流动放电-化学发光技术测定O(~3P)和硅烷化学反应速率常数.在293—413K范围内, 结果为k=(1.05±0.36)×10~(-10)exp[(-3.06±0.10) kcal·mol~(-1) /RT] cm~3·molecule~(-1)·s~(-1)并用过渡态理论将上述实验结果外推到200—2000 K范围内. 计算结果以三参数公式表示为: k=7.67×10~(-19) T~(2.59) exp(-720 cal·mol~(-1)/RT) cm~3·molecule~(-1)·s~(-1). 相似文献
974.
使用MS 80型Calvet微量热计, 在25 ℃, 0.1mol·dm~(-3)(NaClO_4)的50%(V/V)二氧六环溶液中, 测定了镍(Ⅱ)-N,N′-双(对位取代苯基)乙二胺二元及镍(Ⅱ)-2,2′-联吡啶-N,N′-双(对位取代苯基)乙二胺三元体系的生成热和N,N′-双(对位取代苯基)乙二胺的质子化热, 发现在二元和三元配合物的生成热、生成熵与配体的质子化热及质子化熵之间存在较好的线性关系。 相似文献
975.
芳基三氮烯4-位取代基对抗癌活性影响的构象分析 总被引:1,自引:0,他引:1
传统的药物设计和新药开发主要是依靠随机筛选,这种方法误差大,且需要费大量时间和经费,其结果也经常不能达到预期的设想。即使是一个国际性的大制药集团,每年平均要合成上万个化合物才能从中筛选出一个可以成为商品的新药。这种状况迫使我们去寻找一条新的打破常规的途径研究新药。近年来,随着计算机图形系统的广泛应用,对药物构效关系的研究得到了卓有成效的发展,取得了一些成功的例子。如抗菌抗癌琥珀酰-L脯氨酸就是计算化学与分子图形技术相结合的成果,目前已投放市场。 相似文献
976.
977.
An efficient and simple oil bath method for rapid synthesis of graphene/BiOI as visible light active photocatalyst was described. The resultant graphene/BiOI composites were characterized by different techniques, including scanning electron microscopy, X-ray diffraction, and ultraviolet-visible diffuse reflectance spectroscopy. The photocatalytic activity of the as-prepared graphene/BiOI composites for methyl orange degradation was also investigated under visible light irradiation. The results show that BiOI and graphene taken with a mass ratio of 100: 1 exhibited the highest photocatalytic efficiency, which is two times that of pure BiOI. Part of this effect results from higher specific surface area that provides an increased number of active sites. A relatively narrow band gap (2.08 eV) formed in the heterostructure can also contribute to this effect. A suggestion of the photocatalytic mechanism was also offered. 相似文献
978.
Wei Jiang Hongping Li Sheng Yin Xin Wang Wei Liu Hui Liu Wenshuai Zhu Huaming Li 《应用有机金属化学》2016,30(9):753-758
Two hexacyanoferrate‐based ionic liquids, [C4Py]3Fe(CN)6 and [C16Py]3Fe(CN)6, were synthesized and characterized using Fourier transform infrared and mass spectroscopies and CHN analysis. They were employed as Fenton‐like catalysts in extraction and catalytic oxidative desulfurization of model oil with dibenzothiophene (DBT), benzothiophene (BT), 4,6‐dimethyldibenzothiophene (4,6‐DMDBT), 4‐methyldibenzothiophene (4‐MDBT) and 3‐methylbenzothiophene (3‐MBT) as substrates. Various polar solvents, such as ionic liquids, water and organic solvents, were applied to choose a suitable extractant. The results showed the removal of DBT reached 97.1% with [C4Py]3Fe(CN)6 as a catalyst and 1‐n‐octyl‐3‐methylimidazolium hexafluorophosphate ([C8mim]PF6) as an extractant under optimal conditions. The activity of sulfur removal followed the order DBT > 3‐MBT > BT > 4‐MDBT >4,6‐DMDBT. The effect of water content on sulfur removal was investigated by adding various concentrations of H2O2. It was found that excess water had a positive effect on sulfur removal but the catalysts were less sensitive than [FeCl4?]‐based catalysts to water. The mechanism was studied using electron spin‐resonance spectroscopy and gas chromatography–mass spectrometry. O2?? may be the active oxygen species in the catalytic oxidative desulfurization process and the oxidation products of various sulfur compounds were the corresponding sulfoxides and sulfones. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
979.
The chaotic dynamics of a Josephson junction with a ratchet potential and current-modulating damping are studied. Under the first-order approximation, we construct the general solution of the first-order equation whose boundedness condition contains the famous Melnikov chaotic criterion. Based on the general solution, the incomputability and unpredictability of the system’s chaotic behavior are discussed. For the case beyond perturbation conditions, the evolution of stroboscopic Poincaré sections shows that the system undergoes a quasi-periodic transition to chaos with an increasing intensity of the rf-current. Through a suitable feedback controlling strategy, the chaos can be effectively suppressed and the intensity of the controller can vary in a large range. It is also found that the current between the two separated superconductors increases monotonously in some specific parameter spaces. 相似文献
980.