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1.
2.
The first synthesis of “α-methylene-γ-phostones” (propylphostonates) using dimethyl bromo-3-propen-2 ylphosphonate and ketones and aldehydes, in the presence of zinc, is described. 相似文献
3.
Christophe Collard Bernadette Miara 《Archive for Rational Mechanics and Analysis》1999,148(3):233-264
. In this paper, we identify the limiting stress tensor of a thin elastic shell whose thickness approaches zero. In the linear
case, we use a convergence result established for the displacement field in order to get the convergence of the contravariant
components of the linearised stress tensor. In the nonlinear case, the identification of the first Piola‐Kirchhoff stress
tensor is made through a formal asymptotic analysis. In both cases, we show that these limiting stress fields depend on the
geometry of the shell and on the boundary conditions.
(Accepted June 1, 1998) 相似文献
4.
Daniel M. Connor Robert M. Kriegel David M. Collard Charles L. Liotta David A. Schiraldi 《Journal of polymer science. Part A, Polymer chemistry》2000,38(8):1291-1301
Diacids of fused arenes have been prepared for use as covalently bound fluorescent optical brightening agents in condensation polymers. The monomers: dimethyl 1,6‐pyrene dicarboxylate, dimethyl 1,8‐pyrenedicarboxylate, dimethyl 2,7‐pyrenedicarboxylate, 1,8‐bis(2‐carboxybenzoyl)pyrene dimethyl ester, dimethyl 2,6‐anthracenedicarboxylate, dimethyl 2,7‐anthracenedicarboxylate and dimethyl 9,10‐anthracenedicarboxylate are copolymerized with poly(ethylene terephthalate) and their optical properties are assessed. All of the polymers give blue fluorescence, with the copolymer containing dimethyl 1,6‐pyrenedicarboxylate being the brightest. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1291–1301, 2000 相似文献
5.
Spatially periodic patterning of the anchoring condition of a nematic liquid crystal (NLC) within a polymer matrix via a patterned photopolymerization affords a novel and facile method to prepare electrically switchable diffraction gratings. UV irradiation through a photomask of two comonomers, with opposite tendencies to align the NLC and also with different reactivity ratios, leads to definition of areas with either homeotropic or planar alignment of the NLC. Photopolymerization-induced diffusion of the monomers accounts for the spatial distribution of the concentration of these monomers. The resulting diffraction gratings are switchable under low electric fields and possess structural stability offered by the polymer matrix. 相似文献
6.
Jagtap SP Mukhopadhyay S Coropceanu V Brizius GL Brédas JL Collard DM 《Journal of the American Chemical Society》2012,134(16):7176-7185
In this work, a bicyclo[4.4.1]undecane scaffold is used to hold oligo(phenylene ethynylene) units in a cofacially stacked arrangement along the entire length of the conjugated units. We study the impact that the resulting strong interchain interactions have on the photophysical properties. The length of the individual oligomer branches was varied from three to five rings to investigate the effect of conjugation on the electronic properties of the stacked segments. Absorption and fluorescence spectra were recorded and compared to those of the corresponding unstacked analogues. Time-dependent density functional theory calculations were carried out and helped to rationalize the low-energy features present in the fluorescence spectra of the stacked systems. The calculations indicate that the low-energy emissions are due to the presence of excimer-like states. The stronger intensity of the low-energy fluorescence band observed in the five-ring stacked system compared to the three-ring analogue is attributed to the smaller activation barrier that separates the local intrachain state and the excimer-like state in the former compound. 相似文献
7.
Michael R. Hibbs Jeremy Holtzclaw David M. Collard Richard Y. F. Liu Anne Hiltner Eric Baer David A. Schiraldi 《Journal of polymer science. Part A, Polymer chemistry》2004,42(7):1668-1681
The synthesis and properties of poly(ethylene terephthalate) (PET) copolymers containing four bisester diamide structural units are reported. Two of the bisester diamides consist of three para‐substituted aromatic rings, and the other two consist of three meta‐substituted aromatic rings. The copolymers have been characterized by nuclear magnetic resonance, differential scanning calorimetry, and dilute solution viscometry. Three of the copolymers can be compression‐molded into amorphous films for oxygen barrier testing, and one of these three films can be oriented for additional barrier testing. The three amorphous films all have lower permeabilities than unoriented PET. However, this difference diminishes upon the orientation of the polymer films. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1668–1681, 2004 相似文献
8.
9.
Julien G. Mahy Fabien Deschamps Valérie Collard Christine Jérôme John Bartlett Stéphanie D. Lambert Benoît Heinrichs 《Journal of Sol-Gel Science and Technology》2018,86(3):568-579
In this work, the redispersion of three nanocrystalline TiO2 colloids is studied: one pure and two Fe-doped titania. These three colloids are produced by an easy aqueous sol–gel synthesis using precipitation-acidic peptization of Ti precursor. For the two Fe-doped TiO2, one is doped during synthesis (primary doping) and the other is doped after the synthesis (secondary doping). The initial colloids are composed of crystalline TiO2 particles around 7?nm with good photocatalytic properties, tested on PNP degradation under visible light (wavelength >390?nm). The powders obtained by air drying of these three colloids are redispersed in water to produce colloids, which are compared to the initial colloid produced. For each colloid, five cycles of drying redispersion are achieved. The colloids are characterized by dynamic light scattering, zeta potential measurements, inductively coupled plasma–atomic emission spectroscopy, X-ray diffraction, nitrogen adsorption–desorption measurements, Mössbauer spectroscopy, diffuse reflectance spectroscopy, and photocatalytic tests. The results show that similar products are obtained between the cycles, maintaining homologous properties of colloids. This property of redispersion is mainly due to the acid (HNO3, HCl, or H2SO4) which protonates the surface of the TiO2 nanoparticle leading to high-surface charges and electrostatic repulsions between aggregates. This property can be very useful for industrial applications of this synthesis, especially as it allows the volume and weight to be reduced for transportation and storage. Moreover, results show that the pure TiO2 powder can be doped during its redispersion step. The redispersion of the TiO2 developed here is possible without surface functionalization or multiple step processes, contrary to commercial Degussa P25. A 2-year stability study of all the produced colloids has been performed by following the evolution of the macroscopic aspect and the physicochemical properties of these sols. This study showed high stability of the produced colloids. 相似文献
10.
A room temperature 3-component cascade process involving nucleophilic substitution/carbonylation/amination, catalysed by palladium nanoparticles generated in situ from palladacycle 5, affords isoindolinones in good yields. The conversions correlate with the pKa values of the amines. 相似文献