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1.
Fabiano Severo Rodembusch Ndya Pesce da Silveira Dimitrios Samios Leandra Franciscato Campo Valter Stefani 《Journal of Polymer Science.Polymer Physics》2003,41(4):341-350
The solution behavior of new copolymers of methyl methacrylate and benzazole dyes emitting fluorescence because of an intramolecular proton‐transfer mechanism in the electronically excited state has been investigated by static light scattering, fluorescence spectroscopy, ultraviolet–visible, and gel permeation chromatography. In the dilute regime, with tetrahydrofuran (THF) and chloroform as solvents, the copolymers behave as typical polydisperse linear chains in good solvents. The analysis of the osmotic modulus for concentrated solutions in THF (c ≥ 60 g L?1) indicates the existence of an interchain association mechanism. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 341–350, 2003 相似文献
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L. Avaldi R. Camilloni C. Dal Cappello E. Fainelli A. Lahmam-Bennani G. Stefani 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1990,16(2):107-112
Relative triple differential cross section for the coplanar asymmetric (e, 2e) reaction in argon have been measured at 1.5 KeV incident energy and 40 eV ejected electron energy in several kinematics. Depending on the scattering angle, ? a , the chosen kinematics select either ionising collisions belonging to the Bethe ridge (? a =9.2°) or processes in the intermediate region between the pure dipolar and binary regimes. The more relevant finding is the presence of a minimum in the recoil lobe, almost opposite to the direction of the momentum transfer. This feature is qualitatively explained by a first Born model, which describes the ejected electron by a Coulomb wave-function. This result suggests that in the investigated kinematics the interaction of the slow ejected electron with the residual ion is the dominant effect beyond the first order electron-electron interactions. 相似文献
4.
Diblock copolymers composed of poly(oxy-ethylene) (POE) and poly(dl-lactic acid) segments were synthesized by anionic polymerization of d,l-lactide using the oxyanion formed by reaction of the monohydroxyl monomethoxy-poly(ethylene glycol) on sodium hydride. For comparison, a similar copolymer was prepared by using tin octoate to catalyze the lactide polymerization. The copolymers were used to make nanoparticles, which were stored at 4 °C. After a few months under these storage conditions, a dramatic decrease of the poly(ethylene glycol) content was observed, however, the mean diameter of the nanoparticles was not affected. The degradation of the nanoparticles was investigated in vitro under conditions selected to mimic physiological conditions. Changes of characteristics were monitored by 1H NMR, SEC, DLLS and CZE on nanoparticles and/or on the degradation by-products dissolved in the ageing medium. According to their nanometric dimensions, the microparticles degraded very slowly and there was no difference in behaviour between the sodium hydride and the stannous octoate-derived copolymers. 相似文献
5.
L De Boni L T Fran?a H P Grieneisen M Janowicz T B Kist A R Consiglio J R Schoffen V Stefani C Termignoni 《Electrophoresis》1999,20(12):2493-2500
The phenomenon of electrophoresis in free solution has been studied theoretically down to the molecular level for decades. In addition, intermolecular photo-induced proton transfer reactions, which occur in a wide class of molecules (phenols and aminoarenes) as well as proteins (green fluorescent protein), were also studied extensively. However, the study of the effect of light-induced electrophoretic mobility changes of the analytes in electrophoresis was begun only recently. In the present work, capillary zone electrophoresis was chosen as the environment to measure the magnitude of these electrophoretic mobility shifts induced by light. Background electrolytes (running electrolytes) with high refractive indices were developed, allowing the capillary to work like an optical fiber. The experimental conditions for obtaining stable coupling and guided laser light along the liquid core are discussed. Experimental evidence of band compression is observed, leading to a solitary wave behavior of the analyte band (2-naphthol). These solitary waves result from competition between thermal diffusion (dispersion mechanism) and a nonlinear (band compression) effect due to the combined electrophoresis phenomenon and absorption of guided light by the molecules of the band (which are subjected to a "reversible intermolecular proton transfer reaction" as one of their decay routes). The possibilities of applying this effect to different methods and techniques are also discussed. 相似文献
6.
Hélio A. Stefani Claudio M.P. Pereira Roberta B. Almeida Karla P. Guzen 《Tetrahedron letters》2005,46(40):6833-6837
The 4-halo-3,5-dimethyl pyrazoles have been synthetisized in good yields in short reaction times in the absence of a catalyst by reaction of 3,5-dimethyl pyrazoles with N-halosuccinimides (NBS, NCS and NIS) under ultrasound irradiation. Finally, the halogenation of pyrazoles with Br2, ICl and I2 was showed in similar conditions. 相似文献
7.
We performed ab initio molecular orbital (MO) calculations using Hartree—Fock SCF, and second- and fourth-order Møller—Plesset perturbation theory for hydrogen migration reactions on the singlet vinyl fluoride potential energy surface. We used different basis sets and polarization functions to obtain the stationary point geometries and activation barriers. Basis set and the polarization function extension have small effects, while the correlation energy evaluation leads to new conclusions for one of the studied reactions: the product singlet CHCH2F is not a true local minimum on the potential energy surface. 相似文献
8.
Hélio A. Stefani Amna N. Khan Flávia Manarin Pedro H. Vendramini Marcos N. Eberlin 《Tetrahedron letters》2013
A simple protocol which led to an effective construction of α-alkenyl-α-amino esters was achieved under mild conditions. This transformation proceeded by Yb-catalyzed addition of alkenyltrifluoroborates across the imine double bond. A variety of functional groups could be applicable to both partners. 相似文献
9.
Dihalocarbenes generated under phase transfer conditions add to cis and trans vinylic selenides to give the corresponding 1,1-dihalo-2-selenocyciopropanes with retention of configuration. 相似文献
10.
An easy and mild two-step one-pot reaction allowed the synthesis of functionalized N-triazolyl maleimide. Next, the addition of propargyl alcohol and propargyl amine to the N-acyliminium ion mediated by Lewis acid, In(OTf)3, allowed the introduction of a second 1,2,3-triazol ring at position 5 of the amide. The products in both reactions were achieved in moderate to good yields. 相似文献