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991.
Yasemin Fadil S. H. C. Man Florent Jasinski Hideto Minami Stuart C. Thickett Per B. Zetterlund 《Journal of polymer science. Part A, Polymer chemistry》2017,55(14):2289-2297
A convenient and industrially scalable method for synthesis of homogeneous nanocomposite films comprising poly(styrene‐stat‐butyl acrylate) and nanodimensional graphene oxide (GO) or reduced GO (rGO) is presented. Importantly, the nanocomposite latex undergoes film formation at ambient temperature, thus alleviating any need for high temperature or high pressure methods such as compression molding. The method entails synthesis of an aqueous nanocomposite latex via miniemulsion copolymerization relying on nanodimensional GO sheets as sole surfactant, followed by ambient temperature film formation resulting in homogeneous film. For comparison, a similar latex obtained by physical mixing of a polymer latex with an aqueous GO dispersion results in severe phase separation, illustrating that the miniemulsion approach using GO as surfactant is key to obtaining homogeneous nanocomposite films. Finally, it is demonstrated that the GO sheets can be readily reduced to rGO in situ by heat treatment of the film. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2289–2297 相似文献
992.
993.
Dr. Bo Chen Cheng Fang Prof. Peng Liu Prof. Joseph M. Ready 《Angewandte Chemie (International ed. in English)》2017,56(30):8780-8784
We describe the synthetically useful enantioselective addition of Br−CX3 (X=Cl or Br) to terminal olefins to introduce a trihalomethyl group and generate optically active secondary bromides. Computational and experimental evidence supports an asymmetric atom-transfer radical addition (ATRA) mechanism in which the stereodetermining step involves outer-sphere bromine abstraction from a [(bisphosphine)RhIIBrCl] complex by a benzylic radical intermediate. This mechanism appears unprecedented in asymmetric catalysis. 相似文献
994.
利用电子自旋共振谱和X射线光电子能谱研究了二硫化钼MoS_2摩擦表面的氧化和电子转移,发现MoS_2在摩擦过程中是以Mo ̄(4+)经由Mo ̄(5+)过渡态继而与氧作用生成稳定的Mo ̄(6+),并且是以MoO_3的形式存在,证明MoS_2的摩擦表面除有一般认为的Mo ̄(4+)和Mo ̄(6+)这两种化学状态以外,还有Mo ̄(5+)自由基离子这种从未发现的的中间态。Mo ̄(5+)是4d ̄1电子构型,其在室温下于空气或氧气中是稳定的,然而在摩擦环境或添加剂的作用下,Mo ̄(5+)所含不成对电子很容易发生转移而生成Mo ̄(6+),这种研究结果更加深入地揭示了MoS_2摩擦表面氧化过程的复杂性,因此,应当从摩擦化学角度重新认识MoS_2摩擦氧化产物及其形成机制,这于研究摩擦环境和添加剂对润滑剂的抗氧化协同效应具有重要意义。 相似文献
995.
二硫化钼润滑失效的单电子转移机理研究 总被引:1,自引:3,他引:1
MoS2是一种性能优良的固体润滑剂,为了考察它的润滑失效机理,在给定的试验条件下,对其在不同温度大气环境中的氧化状态与活性作了顺磁共振和X射线光电子能谱分析研究.在Mo混合氧化物的Mo3d包络峰中解叠出2组峰,分别归属Mo6+,Mo5+和Mo4+这3种化学状态,Mo5+在4d轨道上有1个未成对的电子,这是Mo氧化物中的一种过渡化合状态,具有4d电子构型和顺磁性,可以在从室温到500℃范围内稳定存在,而且活性较好,在光电离作用下形成Mo的终态化合物.因此,MoS2在摩擦过程中由于周围环境和摩擦热等多种因素的作用,在摩擦表面生成Mo6+而失效,这是一种单电子转多过程 相似文献
996.
997.
Gorkem Yilmaz Alev Tuzun Yusuf Yagci 《Journal of polymer science. Part A, Polymer chemistry》2010,48(22):5120-5125
A thioxanthone (TX) derivative with the additional carbazole chromophore, namely thioxanthone‐carbazole (TX‐C) was synthesized and characterized. The photophysical properties and its efficiency to polymerize methyl methacrylate both in the presence and absence of N,N‐dimethylaniline (DMA) as coinitiator was investigated and compared with that of the commercially available TX. TX‐C was found to display better photophysical properties and in both cases initiate polymerization more efficiently. Detailed real‐time Fourier transform infrared studies revealed that high polymerization rates can be obtained when TX‐C in conjunction with DMA was used. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
998.
Isabelle Minet Laszlo Hevesi Manuel Azenha Joseph Delhalle Zineb Mekhalif 《Journal of chromatography. A》2010,1217(17):2758-2767
We report on the fabrication and performances of a solid-phase microextraction (SPME) fiber based on a stainless steel wire coated with a covalently attached polyacrylonitrile (PAN)/multi-walled carbon nanotubes (MWCNTs) composite. This new coating is obtained by atom transfer radical polymerization (ATRP) of acrylonitrile mixed with MWCNTs. ATRP is initiated from 11-(2-bromo-2-methylpropionyloxy)-undecyl-phosphonic acid molecules grafted on the wire surface via the phosphonic acid group. The extraction performances of the fibers are assessed on different classes of compounds (polar, non-polar, aromatic, etc.) from water solutions by headspace extraction. The optimization of the parameters affecting the extraction efficiency of the target compounds was studied as well as the reproducibility and the repeatability of the fiber. The fibers sustain more than 200 extractions during which they remain chemically stable and maintain good performances (detection limits lower than 2 μg/l, repeatability, etc.). Considering their robustness together with their easy and inexpensive fabrication, these fibers could constitute promising alternatives to existing products. 相似文献
999.
C. Belon X. Allonas C. Croutxé‐barghorn J. Lalevée 《Journal of polymer science. Part A, Polymer chemistry》2010,48(11):2462-2469
Triphenylphosphine (TPP) was used in free‐radical UV‐curable resins to reduce oxygen inhibition effect. The relative influence of concentration, monomer viscosity, light intensity and sample thickness on TPP efficiency was investigated by real time infrared spectroscopy. It is shown that TPP is an effective oxygen scavenger. The mechanism was investigated by means of Laser Flash Photolysis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2462–2469, 2010 相似文献
1000.