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61.
JM Pakarinen H Moisio S Holopainen P Vainiotalo 《Rapid communications in mass spectrometry : RCM》1999,13(14):1485-1490
2-Methoxyethanol chemical ionization of amines, carboxylic acids and amino acids has been found to produce numerous adduct ions. The most intense adduct ions for amines are [M + H](+) and [M + 77](+), for carboxylic acids [M + 27](+), [M + 59](+) and [M + 77](+), and for amino acids [M + H](+), [M + 13](+), [M + 27](+) and [M + 77](+). Either the adduct ion [M + H](+) or [M + 77](+) was the most abundant ion found for amino acids. The proton affinities of amino acids are noticed to control the formation of the [M + H](+) and [M + 77](+) ions. The relative abundance of [M + 13](+) and [M + 27](+) ions varied for different amino acids being most intense for phenylalanine and aspartic acid. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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Time-resolved Raman scattering measurements were performed on ammonium perchlorate (AP) single crystals under stepwise shock loading. For particular temperature and pressure conditions, the intensity of the Raman spectra in shocked AP decayed exponentially with time. This decay is attributed to shock-induced chemical decomposition in AP. A series of shock experiments, reaching peak stresses from 10-18 GPa, demonstrated that higher stresses inhibit decomposition while higher temperatures promote it. No orientation dependence was found when AP crystals were shocked normal to the (210) and (001) crystallographic planes. VISAR (velocity interferometer system for any reflector) particle velocity measurements and time-resolved optical extinction measurements carried out to verify these observations are consistent with the Raman data. The combined kinetic and spectroscopic results are consistent with a proton-transfer reaction as the first decomposition step in shocked AP. 相似文献
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Matthew D. Green Michael H. Allen Jr. Joseph M. Dennis David Salas-de la Cruz Renlong Gao Karen I. Winey Timothy E. LongAuthor vitae 《European Polymer Journal》2011,47(4):486-496
Controlled radical polymerization (CRP) allows for the design and synthesis of functional polymers with tailored composition and unique macromolecular architectures. Synthetic methods that are readily available for controlled radical polymerization include nitroxide-mediated polymerization, reversible addition–fragmentation chain transfer polymerization, and atom transfer radical polymerization. N-Vinyl monomers that are typically amenable to free radical methods are often difficult to synthesize in a controlled manner to high molecular weight due to the lack of resonance stabilization of the propagating radical. However, recent advances in the field of CRP have resulted in successful controlled polymerization of various N-vinyl heterocyclic monomers including N-vinylcarbazole, N-vinylpyrrolidone, N-vinylphthalimide, and N-vinylindole. The incorporation of the imidazole ring into homopolymers and copolymers using conventional free radical polymerization of N-vinylimidazole monomer is particularly widespread and advantageous due to facile functionalization, high thermal stability, and the relevance of the imidazole ring to many biomacromolecules. Copolymers prepared with methyl methacrylate displayed random incorporation according to differential scanning calorimetry and amorphous morphologies according to X-ray scattering. Imidazole- and imidazolium-containing monomers have shown recent success for CRP; however, the controlled polymerization of N-vinylimidazole has remained relatively unexplored. Future efforts focus on the development of tailored imidazole-containing copolymers with well-defined architectures for emerging biomedical, electronic and membrane applications. 相似文献
66.
Hall LM Seitz ME Winey KI Opper KL Wagener KB Stevens MJ Frischknecht AL 《Journal of the American Chemical Society》2012,134(1):574-587
We perform a comprehensive set of coarse-grained molecular dynamics simulations of ionomer melts with varying polymer architectures and compare the results to experiments in order to understand ionic aggregation on a molecular level. The model ionomers contain periodically or randomly spaced charged beads, placed either within or pendant to the polymer backbone, with the counterions treated explicitly. The ionic aggregate structure was determined as a function of the spacing of charged beads and also depends on whether the charged beads are in the polymer backbone or pendant to the backbone. The low wavevector ionomer peak in the counterion scattering is observed for all systems, and it is sharpest for ionomers with periodically spaced pendant charged beads with a large spacing between charged beads. Changing to a random or a shorter spacing moves the peak to lower wavevector. We present new experimental X-ray scattering data on Na(+)-neutralized poly(ethylene-co-acrylic acid) ionomers that show the same two trends in the ionomer peak, for similarly structured ionomers. The order within and between aggregates, and how this relates to various models used to fit the ionomer peak, is quantified and discussed. 相似文献
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本文报导了采用氩离子激光器来泵浦Rr ̄(3+):YLF晶体,应用声光调制器实现了主动锁模;同时应用振动─高反射平面镜也实现了被动锁模,两种锁模均得到了ps光脉冲。据作者了解这是这种晶体材料的第一次锁模运转。 相似文献
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Alves GA Amato S Anjos JC Appel JA Astorga J Bracker SB Cremaldi LM Dagenhart WD Darling CL Dixon RL Errede D Fenker HC Gay C Green DR Jedicke R Karchin PE Kennedy C Kwan S Lueking LH de Mello Neto JR Metheny J Milburn RH de Miranda JM da Motta Filho H Napier A Passmore D Rafatian A dos Reis AC Ross WR Santoro AF Sheaff M Souza MH Spalding WJ Stoughton C Streetman ME Summers DJ Takach SF Wallace A Wu Z 《Physical review letters》1996,77(12):2392-2395
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