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排序方式: 共有252条查询结果,搜索用时 281 毫秒
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A comprehensive investigation of aqueous microemulsion polymerization of butyl acrylate at high surfactant concentrations by means of reaction calorimetry and dynamic light scattering revealed unexpected results with regard to polymerization kinetics and colloidal properties of the final latexes. Particularly, with increasing surfactant concentrations, a decrease in the overall rate of polymerization accompanied by an increasing incubation time of the polymerization and increasing average particle sizes in the final latexes has been observed. Based on reviewing former results on microemulsions and microemulsion polymerizations published in the open literature and the presentation of new experimental results an attempt is made to explain the experimental results consistently with a particle nucleation mechanism based on the classical nucleation theory. To cite this article: K. Tauer et al., C. R. Chimie 6 (2003). 相似文献
94.
Jorge E. Puig Eduardo Mendizbal Santiago Delgado Jesús Arellano Francisco Lpez-Serrano 《Comptes Rendus Chimie》2003,6(11-12):1267-1273
The polymerization of styrene in o/w microemulsions stabilized with dodecyltrimethylammonium bromide (DTAB) with or without cosurfactant (n-butanol, n-hexanol or n-octanol) is examined here. The addition of a cosurfactant enhances the one-phase region in the order: n-butanol > n-hexanol > n-octanol. The kinetics of polymerization slows down in the presence of the alcohol. With the alcohol, the molar masses increase, but no particular trend was noticed on particle size of the lattices. However, by changing the surfactant counter-ion to chloride, alcohol effects on the kinetics almost vanish. Possible explanations to these results are given here. To cite this article: J.E. Puig et al., C. R. Chimie 6 (2003). 相似文献
95.
Mini-emulsion polymerisation of styrene or methylmethacrylate, initiated with ammonium persulphate, have been carried out, in the presence of hexadecane or of polymethylmethacrylate as hydrophobic costabilizer, and the simple hemiester of linear dodecyl alcohol and maleic anhydride, or polymerisable surfactants (surfmers) derived from the condensation of succinic anhydride and either hydroxy propylmethacrylate (MAES), or hydroxyethylmethacrylate (ABS). While the pure surfmers have not so good surface activity, from surface tension measurements, stable mini-emulsion droplets are obtained using a mixture with low amounts of SDS, which have diameters of about 100–200 nm, which remain stable upon polymerisation. Most of the surfmers remain grafted onto the particle surface, thus conferring to these particles strong stability in the various tests. However, due to the high water solubility of the surfmers, another part remains in the serum as unconverted monomer or water-soluble polymers. To cite this article: A. Guyot et al., C.R. Chimie 6 (2003). 相似文献
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中性束加热将应用于先进实验超导托卡马克装置中, 在改善等离子性能的同时也会激发起多种阿尔文不稳定性. 本文主要采用了数值模拟的方法在理论上研究了中性束注入时在台基区激发的离散阿尔文本征模(αTAE) 和环效应阿尔文本征模(TAE), 结果表明在这个区域会激发出丰富的离散阿尔文不稳定性, 这种离散阿尔文不稳定性不同于传统的TAE, 这种模式是俘获在气球模驱动势阱中的束缚态, 由于气球模势阱的存在使它和连续谱解耦, 从势阱中漏出去的能量可以忽略不计, 和TAE类似都很容易被激发, 这种模式可以存在于gap内, 也可以存在于gap外, 频谱更宽泛. 注入功率越大这种不稳定性增长率越大. 这种不稳定性可能会影响等离子体的物理行为, 从而影响等离子体的约束. 相似文献
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Goreti Ribeiro Morais 《Tetrahedron letters》2009,50(14):1642-2044
Application of the Lewis acid BF3·Et2O to the selective synthesis of 5-acetamido-2,6-anhydro-3,5-dideoxy-d-glycero-d-galacto-non-2-enonic acid (Neu5Ac2en) and the related oxazoline, methyl 7,8,9-tri-O-acetyl-2,3,4,5-tetradeoxy-2,3-didehydro-2,3-trideoxy-4′,5′-dihydro-2′-methyloxazolo[5,4-d]- d-glycero-d-talo-non-2-enonate is described. 相似文献
100.
《Comptes Rendus Physique》2018,19(3):146-158
A rapid increase in the performance and quality of white LED light sources has changed the dynamics of electricity access in the last 10 years, reaching tens of millions of people with electric light who previously had no viable alternatives to fuel-based lighting, which is dangerous and expensive. Eliminating fuel-based lighting is a key public health, safety, social equality, and environmental opportunity that is now achievable. Technology advances in LEDs, other super-efficient appliances, solar photovoltaic generation, advanced batteries, and coordinating information technology systems have combined to significantly expand the reach of off-grid energy systems. With support and effort, it is plausible that small “pico-solar” and “solar home” systems could serve over a billion people within a generation, providing basic but highly valued services. Continued progress can be achieved with attention to continued improvements in technology, supporting a growing range of new businesses and enterprises in energy access markets, and synergy with broader human development effort around access to clean water, financial inclusion, and fair access to resources. 相似文献