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1.
A new diamine monomer containing flexible sulfone, sulfide, and amide units was prepared via three steps. Nucleophilic chloro displacement reaction of 4‐aminothiophenol with 4‐nitrobenzoyl chloride in the presence of propylene oxide afforded N‐(4‐mercapto‐phenyl)‐4‐nitrobenzamide and subsequent reduction of the nitro intermediate led to 4‐amino‐N‐(4‐mercapto‐phenyl)benzamide. Two moles of this amino thiophenol compound was reacted with bis‐(4‐chloro phenyl)sulfone to provide a novel diamine monomer. The diamine was reacted with aromatic dianhydrides to form polyimides via a two‐step polycondensation method, formation of poly(amic acid)s, followed by chemical imidization. The resulting polymers were characterized and their physical properties including thermal behavior, thermal stability, solubility and inherent viscosity were studied. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
2.
A series of new poly(amide imide)s was prepared from new diacid containing sulfone, ether, amide and imide groups with various aromatic diamines. The diacid was synthesized via four steps, starting from reaction of 4-aminophenol with 4-nitrobenzoyl chloride in the presence of propylene oxide afforded N-(4-hydroxy phenyl)-4-nitrobenzamide. In the second step, reduction of nitro group resulted in preparation of 4-amino-N-(4-hydroxy phenyl) benzamide. In the next step for the preparation of diamine, the reaction of 4-amino-N-(4-hydroxy phenyl) benzamide with bis-(4-chlorophenyl) sulfone in the presence of K2CO3 was achieved. The prepared sulfone ether amide diamine was reacted with two moles of trimellitic anhydride to synthesize related sulfone ether amide imide diacid. The precursors and final monomer were characterized by FT-IR, H-NMR and elemental analysis. Direct polycondensation reaction of the sulfone ether amide imide diacid with different diamines in the presence of triphenyl phosphite afforded five different poly (sulfone ether amide imide amide)s. The obtained polymers were fully characterized and their physical properties including thermal behavior, thermal stability, solubility, and inherent viscosity were studied. 相似文献
3.
Solid-Phase Microextraction Gas Chromatography for Determination of Some Organophosphorus Pesticides 总被引:1,自引:0,他引:1
A simple and rapid solid-phase microextraction (SPME) method is presented based on activated charcoal–PVC fiber for determination of some organophosphorus pesticides from aqueous samples in direct mode SPME. After optimization of the experimental variables affecting SPME of the target compounds from aqueous solutions, the proposed method was applied to determine pesticides in fruit juice. The analytes in this procedure were preconcentrated for 15 min on the SPME fiber and subsequently desorbed by heating the fiber at 200 °C for 5 min in the GC injection port. Separation was on a capillary column GC followed by flame ionization detection. Recoveries of the pesticides studied in aqueous samples ranged 42%–63% and repeatability for all analytes was < 9% for a single fiber. Fiber-to-fiber reproducibility was < 18%. 相似文献
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Oxidative coupling of methane over (Na2WO4+Mn or Ce)/SiO2 catalysts: In situ measurement of electrical conductivity
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Zeinab Gholipour Azim Malekzadeh Reza Hatami Yadollah Mortazavi Abasali Khodadadi 《天然气化学杂志》2010,19(1):35-42
The effects of manganese oxide or ceria promoters on the performance of Na2WO4/SiO2 catalysts for oxidative coupling of methane (OCM) are reported. The OCM reaction was performed in a continuous-flow microreactor at 800 ℃, atmospheric pressure and under GHSV = 13200 ml gC-1at h-1. Catalysts were characterized by in situ conductivity measurement, FT-IR spectroscopy, XRD, SEM and temperature programmed reduction analysis. Manganese oxide promoted Na2WO4/SiO2 is considered as one of the active and selective ca... 相似文献
6.
In this article we are interested in the density of small linear structures (e.g. arithmetic progressions) in subsets A of the group
\mathbbFpn{\mathbb{F}_{p}^n} . It is possible to express these densities as certain analytic averages involving 1
A
, the indicator function of A. In the higher-order Fourier analytic approach, the function 1
A
is decomposed as a sum f
1 + f
2 where f
1 is structured in the sense that it has a simple higher-order Fourier expansion, and f
2 is pseudo-random in the sense that the k-th Gowers uniformity norm of f
2, denoted by ||f2||Uk{\|{f_2}\|_{U^k}}, is small for a proper value of k. 相似文献
7.
Peyman Afshani Mahsa Ghandehari Mahya Ghandehari Hamed Hatami Ruzbeh Tusserkani Xuding Zhu 《Journal of Graph Theory》2005,49(4):325-335
This paper proves that if G is a graph (parallel edges allowed) of maximum degree 3, then χ′c(G) ≤ 11/3 provided that G does not contain H1 or H2 as a subgraph, where H1 and H2 are obtained by subdividing one edge of K (the graph with three parallel edges between two vertices) and K4, respectively. As χ′c(H1) = χ′c(H2) = 4, our result implies that there is no graph G with 11/3 < χ′c(G) < 4. It also implies that if G is a 2‐edge connected cubic graph, then χ′c(G) ≤ 11/3. © 2005 Wiley Periodicals, Inc. J Graph Theory 49: 325–335, 2005 相似文献
8.
We study the spin thermalization, i.e., the inter-spin energy relaxation mediated by electron–electron scattering in small spin valves. When one or two of the dimensions of the spin valve spacer are smaller than the thermal coherence length, the direct spin energy exchange rate diverges and needs to be regularized by the sample dimensions. Here we consider two model systems: a long quasi-1D wire and a thin quasi-2D sheet. 相似文献
9.
Jin Jingyu Hatami Mohammad Jing Dengwei 《Journal of Thermal Analysis and Calorimetry》2019,135(1):257-269
Journal of Thermal Analysis and Calorimetry - Although there are already many models for prediction of the thermal conductivity of nanoparticle suspension, most of them only consider the cases for... 相似文献
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This paper describes the measurement of induction time in precipitation of silver nanoparticles at different temperatures and supersaturations, and models it with Smoluchowski's coagulation theory. Silver nanoparticles are synthesized by reaction of silver nitrate with hydrazine in the presence of sodium citrate as stabilizer. The rate of association between clusters is found to depend on temperature and their sizes. The activation energy for the association between two clusters and interfacial tension of silver nanoparticles were also estimated. The results also show that induction time decreases with increasing supersaturation and temperature. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献