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1.
Roberto Morales-Cerrada Dr. Christophe Fliedel Dr. Jean-Claude Daran Dr. Florence Gayet Dr. Vincent Ladmiral Dr. Bruno Améduri Prof. Rinaldo Poli 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(1):296-308
Thermal decarbonylation of the acyl compounds [Mn(CO)5(CORF)] (RF=CF3, CHF2, CH2CF3, CF2CH3) yielded the corresponding alkyl derivatives [Mn(CO)5(RF)], some of which have not been previously reported. The compounds were fully characterized by analytical and spectroscopic methods and by several single-crystal X-ray diffraction studies. The solution-phase IR characterization in the CO stretching region, with the assistance of DFT calculations, has allowed the assignment of several weak bands to vibrations of the [Mn(12CO)4(eq-13CO)(RF)] and [Mn(12CO)4(ax-13CO)(RF)] isotopomers and a ranking of the RF donor power in the order CF3<CHF2<CH2CF3≈CF2CH3. The homolytic Mn−RF bond cleavage in [Mn(CO)5(RF)] at various temperatures under saturation conditions with trapping of the generated RF radicals by excess tris(trimethylsilyl)silane yielded activation parameters ΔH≠ and ΔS≠ that are believed to represent close estimates of the homolytic bond dissociation thermodynamic parameters. These values are in close agreement with those calculated in a recent DFT study (J. Organomet. Chem. 2018 , 864, 12–18). The ability of these complexes to undergo homolytic Mn−RF bond cleavage was further demonstrated by the observation that [Mn(CO)5(CF3)] (the compound with the strongest Mn−RF bond) initiated the radical polymerization of vinylidene fluoride (CH2=CF2) to produce poly(vinylidene fluoride) in good yields by either thermal (100 °C) or photochemical (UV or visible light) activation. 相似文献
2.
Tuomas Aitasalo Jorma Hls Hgne Jungner Jean-Claude Krupa Mika Lastusaari Janina Legendziewicz Janne Niittykoski 《Radiation measurements》2004,38(4-6):727-730
The UV excited and persistent luminescence properties as well as thermoluminescence (TL) of Eu2+ doped strontium aluminates, SrAl2O4:Eu2+ were studied at different temperatures. Two luminescence bands peaking at 445 and 520 nm were observed at 20 K but only the latter at 295 K. Both Sr-sites in the lattice are thus occupied by Eu2+ but at room temperature efficient energy transfer occurs between the two sites. The UV excited and persistent luminescence spectra were similar at 295 K but the excitation spectra were different. Thus the luminescent centre is the same in both phenomena but excitation processes are different. Two TL peaks were observed between 50 and 250 °C in the glow curve. Multiple traps were, however, observed by preheating and initial rise methods. With longer delay times only the high temperature TL peak was observed. The persistent luminescence is mainly due to slow fading of the low temperature TL peak but the step-wise feeding process from high temperature traps is also probable. 相似文献
3.
Ccile Nouvel Philippe Dubois Edith Dellacherie Jean‐Luc Six 《Journal of polymer science. Part A, Polymer chemistry》2004,42(11):2577-2588
The whole controlled synthesis of novel amphiphilic polylactide (PLA)‐grafted dextran copolymers was achieved. The control of the architecture of such biodegradable and potentially biocompatible copolymers has required a three‐step synthesis based on the “grafting from” concept. The first step consisted of the partial silylation of the dextran hydroxyl groups. This protection step was followed by the ring‐opening polymerization of D ,L ‐lactide initiated from the remaining OH functions of the partially silylated polysaccharide. The third step involved the silylether group deprotection under very mild conditions. Based on previous studies, in which the control of the first step was achieved, this study is focused on the last two steps. Experimental conditions were investigated to ensure a controlled polymerization of D ,L ‐lactide, in terms of grafting efficiency, graft length, and transesterification limitation. After polymerization, the final step was studied in order to avoid degradation of both polysaccharide backbone and polyester grafts. The chemical stability of dextran backbone was checked throughout each step of the synthesis. PLA‐grafted dextrans and PLA‐grafted (silylated dextrans) were proved to adopt a core‐shell conformation in various solvents. Furthermore, preliminary experiments on the potential use of these amphiphilic grafted copolymers as liquid/liquid interface stabilizers were performed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2577–2588, 2004 相似文献
4.
5.
Dilyana Paneva Laetitia Mespouille Nevena Manolova Philippe Dege Iliya Rashkov Philippe Dubois 《Journal of polymer science. Part A, Polymer chemistry》2006,44(19):5468-5479
Polyelectrolyte complexes (PECs) have been prepared from well‐defined (quaternized) poly[2‐(dimethylamino)ethyl methacrylate] (PDMAEMA) and high molecular weight poly(2‐acrylamido‐2‐methylpropane sodium sulfonate) (PAMPSNa) after a thorough study of their viscometric properties. The effect of pH and quaternization degree of PDMAEMA on PECs stoichiometry has been examined. PEC‐based materials have been characterized in terms of thermal stability, equilibrium swelling degree, and free/bound water composition. The stoichiometry and swellability of the physically crosslinked hydrogels obtained from fully quaternized PDMAEMA/PAMPSNa complexes do not depend on pH. In contrast, PECs made of non quaternized PDMAEMA and PAMPSNa are highly affected by pH, and could reversibly disintegrate at pH ≥ 9. Partially quaternized PDMAEMA/PAMPSNa PECs exhibit intermediate properties and form stable loose structures in the whole investigated pH range. Finally, stable dispersions of PECs nanoparticles have been successfully produced from dilute solutions of the complementary polyelectrolytes. The nanoparticle average diameter as determined by dynamic light scattering proved to depend on the molar fraction of DMAEMA‐based subunits and on the initial polyelectrolyte concentration. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5468–5479, 2006 相似文献
6.
7.
Adler J Becker JJ Blaylock GT Bolton T Brient J Browder T Brown JS Bunnell KO Burchell M Burnett TH Cassell RE Coffman D Cook V Coward DH DeJongh F Dorfan DE Drinkard J Dubois GP Eigen G Einsweiler KF Eisenstein BI Freese T Gatto C Gladding G Grab C Hamilton RP Hauser J Heusch CA Hitlin DG Izen JM Kim PC Köpke L Li A Lockman WS Mallik U Matthews CG Mincer AI Mir R Mockett PM Mozley RF Nemati B Odian A Parrish L Partridge R Pitman D Plaetzer SA Richman JD Sadrozinski HF Scarlatella M Schalk TL 《Physical review letters》1989,62(16):1821-1824
8.
Ghandi K Addison-Jones B Brodovitch JC McCollum BM McKenzie I Percival PW 《Journal of the American Chemical Society》2003,125(32):9594-9595
Muoniated free radicals have been detected in muon-irradiated aqueous solutions of acetone at high temperatures and pressures. At temperatures below 250 degrees C, the radical product is consistent with muonium addition to the keto form of acetone. However, at higher temperatures, a different radical was detected, which is attributed to muonium addition to the enol form. Muon hyperfine coupling constants have been determined for both radicals over a wide range of temperatures, significantly extending the range of conditions under which these radicals and the keto-enol equilibrium have been studied. 相似文献
9.
M. Oubaha M. Dubois B. Murphy P. Etienne 《Journal of Sol-Gel Science and Technology》2006,38(2):111-119
A hybrid organic-inorganic material was prepared from the hydrolytic co-condensation of 3-trimethoxysilylpropylmethacrylate
(MAPTMS) and diphenyldiethoxysilane (DPHDES). The synthesis was performed in three steps: (1) MAPTMS pre-hydrolysis, (2) addition
of DPHDES, and (3) further hydrolysis of the obtained mixture. 29Si nuclear magnetic resonance spectroscopy was used to characterise the structural evolution of the mineral network during
the synthesis. It revealed the catalytic effect of DPHDES on the condensation reaction of silanol groups, initially observed
for pre-hydrolysed MAPTMS. In addition, it was clearly demonstrated that the formation of the highest condensed species of
the aromatic oligomers (D2 species) occurred only in the presence of aliphatic oligomers, which decrease the sterical hindrance about the silicon nuclei. 相似文献
10.
Jean-Claude Grenier Grard Schiffmacher Paul Caro Michel Pouchard Paul Hagenmuller 《Journal of solid state chemistry》1977,20(4):365-379
In order to check the extended defect model previously proposed for the nonstoichiometric perovskite AnMnO3n−1 (n 2), the Ca2Ti2−2xFe2xO6−x solid solution has been studied by means of X-ray diffraction and electron microscope investigations. The results show the existence of a continuous evolution (0 x 1) with two different regions. Close to the CaTiO3 composition (0 x 0.40) the oxygen vacancies seem to be randomly distributed and the symmetry remains pseudocubic. In the composition range 0.55 x 1, the electron microscope patterns show an ordering of the defects: the oxygen vacancies are ordered in the (0k0) planes in strings parallel to the [101] direction. It is concluded from these observations that perpendicular to the Oy direction isolated planes of tetrahedra arranged in rows separate planes of corner-linked octahedra. The n = 2; 2.5; 3, et 4 terms of the AnMnO3n−1 series have been identified. C.S. planes characteristic of classical nonstoichiometric oxides with small cations do not appear: instead, tetrahedra planes succeed to the previous octahedra planes as the degree of nonstoichiometry increases.