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71.
Lukas SonnenscheinAndreas Seubert 《Tetrahedron letters》2011,52(10):1101-1104
Procedures for the synthesis of five sulfobetaine monomers as styrene derivatives are given. The five molecules form a homologous row differing in the distance between the inner quaternary amine and the outer sulfonic acid from one methylene group to five methylene groups. Syntheses are achieved by a sequence of nucleophilic substitutions starting from commercially available precursors. 相似文献
72.
A carbon monolith was synthesized via a polymerization–carbonization method, styrene and divinylbenzene being adopted as precursors and dodecanol as a porogen during polymerization. The resultant monolith had bimodal porous substructure, narrowly distributed nano skeleton pores and uniform textural pores or throughpores. The carbon monolith was directly used as an extracting fiber, taking place of the coated silica fibers in commercially available solid-phase microextraction device, for the extraction of phenols followed by gas chromatography–mass spectrometry. Under the studied conditions, the calibration curves were linear from 0.5 to 50 ng mL−1 for phenol, o-nitrophenol, 2,4-dichlorophenol and p-chlorophenol. The limits of detection were between 0.04 and 0.43 ng mL−1. The recoveries of the phenols spiked in real water samples at 10 ng mL−1 were between 85% and 98% with the relative standard deviations below 10%. Compared with the commercial coated ones (e.g. PDMS, CW/DVB and DVB/CAR/PDMS), the carbon monolith-based fiber had advantages of faster extraction equilibrium and higher extraction capacity due to the superior pore connectivity and pore openness resulting from its bimodal porous substructure. 相似文献
73.
Low‐temperature sol–gel transformation of methyl silicon precursors to silica‐based hybrid materials
Veena Dhayal Rakesh Bohra Meena Nagar Ajay Kaushik Sanjay Mathur Sven Barth 《应用有机金属化学》2008,22(11):629-636
Six new methyl silicon (IV) precursors of the type [MeSi{ON?C(R)Ar}3] [when R = Me, Ar = 2‐C5H4N ( 1 ), 2‐C4H3O ( 2 ) or 2‐C4H3S ( 3 ); and when R = H, Ar = 2‐C5H4N ( 4 ), 2‐C4H3O ( 5 ) or 2‐C4H3S ( 6 )] were prepared and structurally characterized by various spectroscopic techniques. Molecular weight measurements and FAB (Fast Atomic Bombardment) mass spectral studies indicated their monomeric nature. 1H and 13C{1H} NMR spectral studies suggested the oximate ligands to be monodentate in solution, which was confirmed by 29Si{1H} NMR signals in the region expected for tetra‐coordinated methylsilicon (IV) derivatives. Thermogravimetric analysis of 1 revealed the complex to be thermally labile, decomposing to a hybrid material of definite composition. Two representative compounds ( 2 and 4 ) were studied as single source molecular precursor for low‐temperature transformation to silica‐based hybrid materials using sol–gel technique. Formation of homogenous methyl‐bonded silica materials (MeSiO3/2) at low sintering temperature was observed. The thermogravimetric analysis of the methylsilica material indicated that silicon‐methyl bond is thermally stable up to a temperature of 400 °C. Reaction of 2 and Al(OPri)3 in equimolar ratio in anhydrous toluene yielded a brown‐colored viscous liquid of the composition [MeSi{ON?C(CH3)C4H3O}3.Al(OPri)3]. Spectroscopic techniques 1H, 13C{1H}, 27Al{1H} and 29Si{1H} NMR spectra of the viscous product indicated the presence of tetracoordination around both silicon and aluminum atoms. On hydrolysis it yielded methylated aluminosilicate material with high specific surface area (464 m2/g). Scanning electron micrography confirmed a regular porous structure with porosity in the nanometric range. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
74.
Monomeric tungsten oxo‐aminoalkoxides W(O)(OPri)3(L) [L = O(CH2)nNMe2; n = 2 (dmae, 1) and 3 (dmap, 2 )] were synthesized by alcohol exchange with [W(O)(OPri)4]2 and characterized spectroscopically. 1, 2 and [W(O)(OPri)4]2 were used as precursors for the aerosol‐assisted chemical vapour deposition of WO3 thin films, which were characterized by glancing angle X‐ray diffraction, SEM and transmission‐reflectance measurements. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
75.
研究了水/ 甲苯乳化液中二苯并噻吩( 硫芴) 在分散型钼酸、磷钼酸和四硫钼酸铵催化剂存在下的加氢脱硫反应. 反应在高压釜中于340 ℃及三种不同的气氛即H2 ,H2/H2 O和CO/H2O(CO 和H2O 经水煤气转换反应( WGSR) 产生原位氢) 的存在下进行. 用GC和GCMS鉴定、分析了气体和液体产物的组成. 结果表明: 对硫芴的加氢脱硫反应,在分散型四硫钼酸铵催化剂存在下,原位产生的氢的效果仅比加入的氢气稍好,而在分散型钼酸和磷钼酸催化剂存在下,原位产生的氢远比加入的氢气有效. 实验结果还表明: 硫化氢能显著提高分散型钼酸和磷钼酸催化剂的加氢脱硫活性,但在分散型四硫钼酸铵催化剂存在下,硫化氢能促进加氢反应而抑制氢解反应. 一氧化碳和水均选择性地抑制氢解反应. 相似文献
76.
Metallic Li in carbonaceous nanostructures was obtained in high concentration (as much as 33.4%) through metalorganic chemical vapor deposition involving certain lithium–aminoalkyl moieties, which are formed in situ , by decomposition of a precursor containing both cobalt and lithium. The bimetallic complex containing both lithium and cobalt was characterized by IR spectroscopy, mass spectroscopy, nuclear magnetic resonance spectroscopy, elemental analysis and thermogravimetric analysis. X‐ray photoelectron spectroscopy measurements performed on the as‐grown films demonstrate that lithium can be stable in metallic form in such a film. Results of X‐ray photoelectron spectroscopic analysis of the as‐grown films are presented as direct evidence of the formation and stabilization of metallic lithium in carbon nanotubes. Carbon nanotubes, encapsulating metallic lithium, can potentially act as a miniaturized nanobattery. Such a battery would be potentially useful in the next generation of communication and remote sensing devices, where a pulse of current is required for their operation. In addition, with metallic lithium, having an effective nuclear magnetic moment, such materials can be envisioned to show potential applications in devices based on nuclear magnetic resonances. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
77.
Akira Matsumoto Hiroyuki Hamamoto Yuta Miwa Hiroyuki Aota Satoshi Inoue Katsutoshi Yokoyama Yasuo Matoba Michirou Shibano 《Journal of polymer science. Part A, Polymer chemistry》2009,47(11):2871-2881
No difference in the actual gel points was substantially observed among three isomeric diallyl phthalates such as diallyl phthalate (DAP), diallyl isophthalate, and diallyl terephthalate (DAT); this interesting gelation behavior was discussed further in terms of the correlation between gelation and the difference in cyclization modes, and also, the difference in reactivity between the uncyclized and cyclized radicals for cross‐linking. In the present work, we tried to extend the preceding discussion to the polymerization of triallyl trimellitate (TAT) because the molecular structure of TAT is presumed to essentially involve the characteristics of three isomeric diallyl phthalates and, therefore, the enhanced gelation was expected in TAT polymerization. However, no enhancement of gelation was observed. For a full understanding of the gelation in multiallyl cross‐linking polymerization, we explored further the polymerizations of DAP, DAT, and TAT, especially focusing on the characterization of resultant network polymer precursors (NPPs) using SEC‐MALLS‐viscometry providing the correlation of [η] versus Mw of fractionated samples. Notably, the structure of NPP consisting of oligomeric primary polymer chains generated from specific allyl polymerization would become core‐shell type dendritic with the progress of polymerization. The correlation between delayed gelation and decreased reactivity of dendritic NPP for intermolecular cross‐linking is discussed. Conclusively, the reactivity for intermolecular cross‐linking between NPPs decreased with the progress of polymerization leading to a delayed gelation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2871–2881, 2009 相似文献
78.
Eri Yoshida 《Colloid and polymer science》2008,286(12):1435-1442
The novel synthesis of polyhedral particles was attained by the dispersion polymerization of styrene in supercritical carbon
dioxide using a polydimethylsiloxane-based macroazoinitiator as a precursor of the surfactant. The macroazoinitiator, VPS-1001,
composed of poly(dimethylsiloxane) and 6-8 molecules of the azo groups served as a precursor of the surfactant for the dispersion
polymerization by azobisisobutylonitrile as an initiator to produce 0.8-4 μm polyhedral particles. The size of the particles
decreased as a result of increasing the VPS-1001 concentration. Too high a concentration of VPS-1001 caused coagulation of
the particles. A decrease in the temperature increased the particle size and size distribution, while a decrease in the pressure
produced particles with nonspecific shapes. An increase in the stirring rotation speed tended to increase the size and size
distribution. However, too high a speed of rotation also caused coagulation of the particles. 相似文献
79.
The humidity and water tolerance of a sol-gel derived binder prepared using a cheap, multicomponent precursor has been studied.
The sol was prepared by dissolving the precursor in water under acidic conditions using either formic acid or a mixture of
formic acid and citric acid for pH adjustments. It is shown that a post-treatment temperature of 400 °C or higher is needed
in order to achieve full binder stability under excess water conditions, as thermal decomposition of metal carboxylates leads
to a pronounced decrease in water solubility of the gels. The mesoporous gel can be made hydrophobic by post-treatments with
either a silane or an organophosphonate, showing that both silica and metal oxides are exposed on the surface of the binder.
Surface functionalization is especially effective for gels heat-treated at higher temperatures where the metal carboxylates
have decomposed to the corresponding oxides or carbonates. The results are expected to be of great importance for the use
of this cheap binder in large scale industrial applications.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
80.
G. C. Boskovic A. R. Zarubica M. N. Kovacevic P. S. Putanov 《Journal of Thermal Analysis and Calorimetry》2008,91(3):849-854
Properties of two catalysts tailored in the laboratory conditions by sulfation of commercial Zr-hydroxide and Zr-hydroxide
of nitrate origin were compared with those of commercial SO4-Zr-hydroxide. Equally thermally treated samples in the temperature interval 500–700°C, and having the same amount of sulfur,
show different properties indicating memory effect of their solid parent materials. The catalyst obtained by sulfation of
commercial Zr-hydroxide differs in amount of residual sulfates upon calcination from other two catalysts. The instability
of sulfates in the previous case might be connected to the lowest surface area values of catalyst and the highest fraction
of monoclinic phase observed at all applied calcination temperatures. 相似文献