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聚合氨基酸催化的α,β-不饱和酮的环氧化反应是由Juliá和Colonna[1]发现的,最初反应是在三相反应体系(聚合氨基酸、有机溶剂和H2O2-H2O-NaOH)中进行的,Adger等[2]对此条件进行了改进.以树脂固定的聚合氨基酸代替聚合氨基酸为手性催化剂;同时分别以Urea-H2O2和DBU代替H2O2和NaOH,使得反应可以在两相(催化剂和有机溶剂)体系进行.这些改进简化了操作,提高了催化剂的回收率,还扩大了反应的应用范围. 相似文献
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《高分子通报》1993,(1)
高分子化学ATSC(丙酮缩氨基硫脲)在氯乙烯聚合中的应用/张泰生(锦西化工总厂)/聚氯乙烯.1992,(2):10~13FTIR研究预辐照PMMA/PU IPNs的反应动力学/王庚超(华东化工学院材料科学研究所)/高分子材料科学与工程.1992,8(2):32~37.钴60γ射线辐照预聚合MMA,用FTIR研究预聚合MMA/PU IPNs的反应动力学,讨论了影响因素IBMA树脂的合成与表征/戚银城(北京化工学院高分子系)/高分子材料科学与工程.1992,8(2):38~43.以异丁烯、马来酸酐为单体,在引发剂存在下淤浆聚合制得IBMA树脂,研究了影响因素 相似文献
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Cu~(2+)离子浓度对Cu~(2+)-Na_2SO_3体系引发甲基丙烯酸甲酯聚合机理的影响 总被引:2,自引:0,他引:2
<正> 氧化还原体系引发乙烯类单体自由基聚合过程中,氧化剂或还原剂浓度的变化可能引起聚合机理的改变,Reddy等研究“铜(Ⅱ)——维生素C-氧”体系引发甲基丙烯酸甲酯的自由基聚合时,发现随着Cu~(2+)离子浓度增加,聚合速度由上升至下降;单体反应级数从3/2增至2.0,我们在空气气氛下,对Cu~(2+)-Na_2SO_3体系引发甲基丙烯酸甲酯聚合进行了研究,亦发现Cu~(2+)离子浓度对聚合速度和聚合机理有很大影响,在较低的Cu~(2+)离子浓 相似文献
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受阻路易斯酸碱对(frustrated Lewis pairs,FLPs)是大位阻的路易斯酸和大位阻的路易斯碱在溶液中受空间位阻因素影响而不能形成配位键所得到的组合。 在这种特殊的组合中,路易斯酸和路易斯碱未能被中和淬灭,依旧保持着的反应活性。 而当H2等小分子靠近时,FLPs可以将H2的化学键异裂,进而得到一个阳离子和一个阴离子。 这种独特的反应特性使得FLPs在催化加氢、小分子气体活化、烯烃聚合和开环聚合等方面展现出了一些具有新特性的研究思想和方法。 尤其是在烯烃聚合和开环聚合中,FLPs具有很强的催化活性。 本文简要介绍了FLPs的发展历史及其在小分子活化中的应用,并重点介绍了其在高分子催化领域中的应用。 相似文献
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超临界CO2在高分子合成与制备中的应用 总被引:6,自引:0,他引:6
介绍超临界二氧化碳流体作为介质在高分子合成与制备中的研究进展。文中表明,可在超临界二氧化碳中实施氟代单体的自由基溶液聚合、甲基丙烯酸甲酯的分散聚合、丙烯酸的沉淀聚合、丙烯酰胺的反相乳液聚合以及异丁基乙烯基醚的阳离子聚合等多种聚合反应,可用超临界二氧化碳溶胀聚合法制备梯度共混物。此外,超临界二氧化碳还可用于聚合物分级和聚合物微孔、微纤与微球材料的制备等,显示出超临界二氧化碳是一种对环境无污染且价廉的 相似文献
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New silicone‐containing polymers with crosslinkable units have been synthesized by hydrosilation polymerization in both toluene and supercritical carbon dioxide (70°C, 3000 psi) catalyzed by platinum‐divinyltetramethyldisiloxane (Pt‐DVTMS). It was found that high molecular polymers were obtained in both toluene and supercritical carbon dioxide. The polymers were characterized by FTIR, NMR, GPC, TGA, and DSC. The molecular weights of these polymers ranged from 9000 to 39,000. With further hydrolysis and thermal curing, the molecular weight can be increased significantly. Comparison of the properties between reactions in toluene versus supercritical carbon dioxide indicated that the green solvent is a usable alternative for hydrosilation polymerization. The new polymers synthesized in either toluene or supercritical carbon dioxide are thermally stable, ranged from 350 to 488°C. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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分子动力学模拟苯和萘在超临界二氧化碳中的无限稀释扩散系数 总被引:5,自引:1,他引:4
采用球型模型和点位-点位模型对超临界二氧化碳的自扩散系数及苯或萘在超临界二氧化碳中的无限稀释扩散系数进行了分子动力学模拟。结果表明,球型模型及点位-点位模型均可较准确地预测二氧化碳的自扩散系数,球型模型因形式简单,准确度相对较差;点位-点位模型准确度虽高,但需较长的模拟机时。两种位能模型所获得的准确度相当,但点位-点位模型可以更精细地反映体系的微观结构。 相似文献
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采用分散聚合和无皂乳液聚合的方法,我们制备了粒径不同的交联聚合物微球。通过改变超临界二氧化碳的压力、处理微球的时间以及实验的温度,我们可以实现对这些微球塑化程度的调节。研究发现,随着超临界二氧化碳压力的升高,其对聚合物微球的塑化能力呈现出先增强后降低的趋势。文中我们对这种现象出现的机理也进行了相应的讨论。随着体系温度的升高或者延长处理微球的时间,超临界二氧化碳对两种微球的塑化能力都呈增强趋势。由于乳液聚合得到的聚合物的分子量通常会比分散聚合得到的聚合物的分子量大,因此在相同的条件下超临界二氧化碳对分散聚合法制备的微球塑化能力更强。 相似文献
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M. S. Kondratenko S. A. Anisenko I. V. Elmanovich A. I. Stakhanov M. O. Gallyamov A. R. Khokhlov 《Polymer Science Series A》2018,60(4):451-458
Comb-shaped copolymers of perfluorohexylethyl methacrylate and methacryloxypropyl-terminated polydimethylsiloxane are synthesized by radical polymerization in supercritical carbon dioxide, solubility of the copolymers in supercritical carbon dioxide is studied, and hydrophobic properties of thin films obtained via precipitation of the copolymers from trifluorotrichloroethane and supercritical carbon dioxide solutions on substrates are examined. On the basis of water and dimethyl sulfoxide contact angle measurements, the specific free surface energy of the formed films is calculated. It is shown that the thin films of the copolymers have a lower surface energy and are characterized by a smaller water contact angle hysteresis than the films based on homopolymer poly(perfluorohexylethyl methacrylate). A comparative testing of coatings based on the homopolymer and copolymer deposited from solutions in supercritical carbon dioxide on the surface of nylon fabrics is performed. It is found that copolymer-coated fabrics have on average higher water contact angles. 相似文献
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Sophie Fortini Frédéric Lavanchy Philip Nising Thierry Meyer 《Macromolecular Symposia》2004,206(1):79-92
Efficient stirring is needed to realize heat flow analysis with a thermally homogeneous medium. Because dispersion polymerization with supercritical fluids can be destabilized under stirring, a preliminary target has been to find a compromise between synthesis and basic reaction calorimetry requirements. This paper describes the use of poly (dimethylsiloxane) macromonomer with a molecular weight 5000 g/mol as stabilizer for the dispersion polymerization of methyl methacrylate in supercritical carbon dioxide. The effect of stirring speed and stabilizer concentration has been examined. This study has shown that poly (methyl methacrylate) can be produced at high yield and molecular weight using 10 wt% (respect to monomer) poly (dimethylsiloxane) macromonomer at stirring speeds up to 600 rpm. A polymerization enthalpy of −57.6±2 kJ/mol has been calculated being in good agreement with previously reported data. Thus, preliminary results for the heat balance using the newly developed high pressure reaction calorimeter for supercritical fluid applications have shown the important potential of reaction calorimetry to promote supercritical fluid technologies at industrial scale allowing for the determination of kinetics and thermodynamic and safety data, respectively. 相似文献
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Teresa Casimiro 《European Polymer Journal》2005,41(9):1947-1953
Herein we report the synthesis of poly(diethylene glycol dimethacrylate), poly(DEGDMA), by free-radical heterogeneous polymerization in supercritical carbon dioxide (scCO2), using a commercially available carboxylic acid end-capped perfluoropolyether oil (Krytox 157FSL) as stabiliser. The effect of initial concentration of stabiliser, monomer and initiator on the yield and morphology of the resulting polymer has been investigated. Krytox worked effectively as a stabiliser and discrete poly(DEGDMA) particles with diameters ranging from 1.28 to 2.08 μm and narrow particle size distribution were produced in supercritical carbon dioxide, in high yield and in short reaction times, without making use of harmful organic solvents. 相似文献