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51.
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David Ribour Roger Spitz Vincent Monteil 《Journal of polymer science. Part A, Polymer chemistry》2010,48(12):2631-2635
Heterogeneous Ziegler‐Natta precatalysts (with phthalate as internal donor) were modified by treatments with various Lewis acids (MCln with M = Ga, Sn, Si, and Sb and n = 3, 4, or 5) before their use in the polymerization of propylene. If performed on previously “detitanated” precatalysts, treatments with SnCl4 and SiCl4 lead to a slight activation but especially to an increase of the tacticity whereas GaCl3 and SbCl5 treatments deactivate the catalyst. The modification method applied to conventional unmodified precatalysts gave similar trends. A significant increase of tacticity (and/or of Tm) and a narrowing of the molecular weight distribution were observed in the case of SnCl4 and SiCl4 treatments. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2631–2635, 2010 相似文献
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Polymerization of Ethylene through Reversible Addition–Fragmentation Chain Transfer (RAFT) 下载免费PDF全文
Dr. Cédric Dommanget Dr. Franck D'Agosto Dr. Vincent Monteil 《Angewandte Chemie (International ed. in English)》2014,53(26):6683-6686
The present paper reports the first example of a controlled radical polymerization of ethylene using reversible addition–fragmentation chain transfer (RAFT) in the presence of xanthates (Alkyl‐OC(?S)S‐R) as controlling agents under relative mild conditions (70 °C, <200 bars). The specific reactivity of the produced alkyl‐type propagating radicals induces a side fragmentation reaction of the stabilizing O‐alkyl Z group of the controlling agents. This fragmentation, rarely observed in RAFT, was proven by NMR analyses. In addition, semicrystalline copolymers of ethylene and vinyl acetate were also prepared with a similar level of control. 相似文献
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C. Duverger M. Montagna R. Rolli S. Ronchin L. Zampedri M. Fossi S. Pelli G. C. Righini A. Monteil C. Armellini M. Ferrari 《Journal of Non》2001,280(1-3):261-268
Silica-based sol–gel glasses activated by Er3+ ions are attractive materials for integrated optics (IO) devices such as frequency upconverters and optical amplifiers. Monolithic erbium-activated silica xerogels with erbium content ranging from 0 up to 40 000 ppm were prepared by the sol–gel technique. Samples were densified by thermal treatment in air at 950°C for 120 h. The densification degree and the relative content of hydroxyl groups were studied by Raman spectroscopy. Refractive indices were measured at 632.8 and 543.5 nm by a prism coupling technique. Green to blue and violet upconversion luminescence upon continuous-wave excitation at 514.5 nm was observed for all samples. Emission at 1.5 μm, characteristic of the 4I13/2→4I15/2 transition of Er3+ ions, was observed at room temperature for all samples upon continuous-wave excitation at 980 nm. For the 5000 Er/Si ppm-doped xerogel, a photoluminescence was observed and a lifetime of 8 ms for the metastable 4I13/2 level was measured. 相似文献
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We have developed a rapid method for the purification of proteins, combining titration curve analysis with a two-step column chromatographic procedure. We have used this approach to purify the cytotoxin (L toxin) from Clostridium sordellii. We have also determined the amino acid composition of this cytotoxin. This toxin has a pI value of 4.20 and an Mr of 260,000, reduction of which results in a band of Mr 43,000 on sodium dodecyl sulphate polyacrylamide gel electrophoresis. Since both the proteins of Mr 260,000 and 43,000 are recognized by the polyclonal anti-C. sordellii L toxin, which neutralizes the L toxin cytotoxicity, we propose a hexameric structure for the protein of Mr 260,000, each subunit being Mr 43,000. 相似文献
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Nie W. Kalisky Y. Pedrini C. Monteil A. Boulon G. 《Optical and Quantum Electronics》1990,22(1):S123-S131
Multisite energy transfer from Cr3+ to Tm3+ was studied using low-temperature high-resolution laser spectroscopy. Selective excitation routes for Tm3+ sites were demonstrated using excitation and emission spectroscopy, and were confirmed by lifetime measurements. 相似文献
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Cr3+ and Nd3+ non-equivalent crystal field sites were observed. By use of a high-resolution dye laser,2E and4A2 splittings, zero-phonon4A2 →2E,2T1,4T2 transitions and vibronic levels of2E doublets of Cr3+ non-equivalent centres were recorded. Energy transfers from Cr3+ multisites to Nd3+ were studied by site-selective spectroscopy and fluorescence decays. 相似文献
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Clément Monteil Nathalie Bar Bernard Moreau Richard Retoux Agnès Bee Delphine Talbot Didier Villemin 《Particle & Particle Systems Characterization》2014,31(2):219-227
Novel partially phosphonated polyethylenimine polymers are developed in order to control the modification of nanoparticle (NP) surfaces. This polymer is built by an accessible one‐step process. The numerous phosphonate functions assume both a strong covalent anchoring on metal oxide NPs and a modulation of electric charges, while amino groups are associated with dispersion preservation and subsequent biofunctionalization. The zwitterionic nanomaterials obtained display a good stability toward pH and ionic strength. According to the selected percentage of phosphonation and the polymer size, zeta potential, and diameter of the particles are controlled. 相似文献