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排序方式: 共有98条查询结果,搜索用时 15 毫秒
1.
Auvergne R. Saint‐Loup R. Joly‐Duhamel C. Robin J. J. Boutevin B. 《Journal of polymer science. Part A, Polymer chemistry》2007,45(7):1324-1335
The synthesis and characterization of photopolymerizable unsaturated polyester resins based on PET waste are described. The resins came from a depolymerization process based on the glycolysis of PET by diethylene glycol (DEG). Different molecular weights of glycolysates were synthesized. Then, the latter was functionalized by a methyl hemiester of maleic acid to obtain unsatured α,ω‐bismaleate PET oligomers. In the presence of an electron donor monomer, such as triethylene glycol divinyl ether, these electron acceptor oligomers were copolymerized by way of charge‐transfer complexes under UV irradiation. The reaction was monitored in situ by real‐time IR spectroscopy to study the kinetics of photopolymerization. This one was studied in relation with the physical and chemical characteristics of oligoesters and the composition of mixtures containing divinyl ethers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1324–1335, 2007 相似文献
2.
Duhamel J Kanagalingam S O'Brien TJ Ingratta MW 《Journal of the American Chemical Society》2003,125(42):12810-12822
The "blob" model, developed to analyze the fluorescence decays of polymers randomly labeled with pyrene, has been applied to a series of pyrene-labeled poly(glutamic acid)s (PyPGA) in DMF and carbonated buffer solutions at pH 9. Poly(glutamic acid) (PGA) exists in the ionized form in the buffer solutions as poly(sodium glutamate) (PGNa). PGA adopts an alpha-helical conformation in DMF, whereas in aqueous solution PGNa is a random coil. Fluorescence, UV-vis absorption, and circular dichroism measurements indicate that in our studies pyrene pendants attached themselves along PGA in a clustered manner. Simulations were carried out to establish that the geometry of the PGA alpha-helix induces the high level of pyrene clustering. Since the level of pyrene clustering decreased with lower pyrene content, information about naked PGA was retrieved by extrapolating the trends obtained by fluorescence to zero pyrene content. Analysis of the fluorescence decays demonstrated that during its lifetime an excited pyrene probes a 32 amino acid section of the PGA alpha-helix. This result was supported by molecular mechanics optimizations. This study establishes that the blob model, originally used to monitor the encounters between pyrenes attached randomly onto a polymer adopting a random coil conformation, can also be applied to study the dynamics of the side chains of structured proteins. Since the blob model helps in monitoring the encounters between amino acids in the initial state (i.e., random coil) and in the final state (i.e., structured protein) of the folding pathway of a protein, it could be applicable to the study of protein folding. 相似文献
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Optically active α-aminoesters are obtained by metalation of the corresponding Schiff bases by chiral lithium amide followed by protonation by an achiral or a chiral acid. 70 % e.e. can be obtained. 相似文献
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M. Buenerd C. Bonhomme D. Lebrun P. Martin J. Chauvin G. Duhamel G. Perrin P. de Saintignon 《Physics letters. [Part B]》1979,84(3):305-308
Inelastic scattering spectra from the (3He, 3He′) reaction at 108.5 MeV have been measured down to 1.85° scattering angle on 90Zr and 208Pb, allowing a giant monopole resonance study in these nuclei. DWBA analysis is reported. 相似文献
7.
Cuauhtémoc Pozos vázquez Russell Tayouo Christine Joly‐Duhamel Bernard Boutevin 《Journal of polymer science. Part A, Polymer chemistry》2010,48(10):2123-2134
The synthesis and characterization of poly(dimethylsiloxanes) bearing maleimides end‐groups (PDMSM) were carried out through imidization of maleic anhydride with three poly(dimethylsiloxanes) diamines of different molecular weights. Self‐photopolymerization of PDMSM was studied by Real‐Time Fourier Transform infrared spectroscopy (RT‐FTIR) and was possible even without photoinitiator (Darocur 1173). The reaction was found to proceed within seconds upon exposure to ultraviolet (UV) radiation to generate highly crosslinked polymer networks. The results indicated that these polymerizations were less sensitive to oxygen inhibition than the radical processes carried out on conventional UV‐curable acrylate resins. The thermal and mechanical properties of these resulting materials were studied starting from PDMS precursors with different molecular weights. These materials exhibit a low glass transition temperature (100 °C) and a high degradation temperature (400 °C) depending on the density of crosslinking points. These PDMSM are suitable as hydrophobic additives in a coating formulation based on a UV cured polypropylene glycol bismaleimide. Only a very small amount of silicone additives (0.3 wt %) is needed to change the wettability on the surface of the films. The migration of the additive was clearly shown before irradiation by scanning electron microscopy EDX and surface energy measurements. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2123–2134, 2010 相似文献
8.
E. Gerlic J. Ka¨llne H. Langevin-Joliot J. Van de Wiele G. Duhamel 《Physics letters. [Part B]》1975,57(4):338-340
Energy spectra have been measured for the (τ, α) reaction at 205 MeV on90Zr, 118,124Sn and 208Pb. Results on the valence neutron shells and on the inner 1f7/2 shell in 90Zr, 1g9/2 subshell in 118,124Sn (T< and T> components) and 1h11/2 subshell in 208Pb are presented. 相似文献
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This paper investigates how solution conditions, especially solvent polarity and hydrogen bonding, affect the fluorescence of ellipticine, a natural plant alkaloid with anticancer activity. A total of 16 solvents that cover a wide range of polarities were tested. The ultraviolet (UV) absorption and fluorescence emission of ellipticine were found to be solvent dependent. The absorption and emission maximum shifted to higher wavelengths (red shift) with increased solvent polarity. The difference in absorption and emission maximum (Stokes' shift) was large, approximately 10,000-11,000 cm-1, in polar solvents (with orientation polarizability Deltaf>0.2) but unusually small, approximately 8900 cm-1, in nonpolar solvents (hexane and cyclohexane). Large Stokes' shifts were due to an intramolecular charge transfer (ICT), which was enabled by large solvent polarity and hydrogen bonding of ellipticine with the solvents. Two transitions were found in the Lippert-Mataga plot between (1) nonpolar and semipolar solvents and between (2) semipolar and polar solvents. The first transition reflected the formation of hydrogen bonds between ellipticine and the solvents whereas the second transition indicated that ellipticine underwent an ICT. In addition, the larger extinction coefficients and the longer lifetime of ellipticine obtained in protic solvents were attributed to the formation of stronger hydrogen bonds. The photophysical response of ellipticine to changes in solvent polarity and hydrogen bond formation could be used to infer the location of ellipticine in a heterogeneous medium, namely liposomes in aqueous solution. A relatively large red shift of emission in liposomes indicated that ellipticine may be in a more polar environment with respect to the lipid bilayer, possibly close to the hydrophilic interface. 相似文献