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排序方式: 共有132条查询结果,搜索用时 22 毫秒
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22.
Nicolas Heureux 《Tetrahedron letters》2005,46(1):79-83
The preparation of the novel trans-1,2-bis-stannylcyclopropane 4 is described. Its applications in Kosugi-Migita-Stille cross-coupling and in tin-lithium exchange reactions are presented and discussed. 相似文献
23.
Photo‐polymerized lauryl methacrylate monolithic columns for CEC using lauroyl peroxide as initiator
Virginia Bernabé‐Zafón Miriam Beneito‐Cambra Ernesto F. Simó‐Alfonso Guillermo Ramis‐Ramos José Manuel Herrero‐Martínez 《Electrophoresis》2009,30(21):3748-3756
Lauryl methacrylate (LMA)‐ester based monolithic columns photo‐polymerized using lauroyl peroxide (LPO) as initiator were prepared, and their morphological and CEC properties were studied. The composition of the polymerization mixture (i.e. ratios of monomers/porogenic solvents, 1,4‐butanediol/1‐propanol and LMA/crosslinker) was optimized. The morphological and chromatographic properties of LMA columns were evaluated by means of SEM pictures and van Deemter plots of PAHs, respectively. The polymerization mixture selected as optimal provided a fast separation of a mixture of PAHs with excellent efficiencies (minimum plate heights of 8.9–11.1 μm). Satisfactory column‐to‐column (RSD<4.5%) and batch‐to‐batch reproducibilities (RSD<6.3%) were achieved. The LMA columns photo‐polymerized with LPO were compared with those prepared with AIBN. Using PAHs, alkylbenzenes and basic compounds for testing, the columns obtained with LPO gave the best compromise between efficiency, resolution and analysis time. 相似文献
24.
Macroreticular cation exchangers can be prepared by polymerizing sulfonated phenols with formaldehyde under acidic conditions. The resins are highly porous with large surface areas. Their properties compare well with those based on styrene and divinylbenzene copolymers. 相似文献
25.
Maria Navarro‐Pascual‐Ahuir Maria J. Lerma‐García Guillermo Ramis‐Ramos Ernesto F. Simó‐Alfonso José M. Herrero‐Martínez 《Electrophoresis》2013,34(6):925-934
In this article, capillary columns constituted by lauryl methacrylate monoliths with embedded silver nanoparticles (AgNPs) were developed and tested. Two incorporation approaches of AgNPs in monoliths were explored. The AgNPs were either photogenerated in situ during polymerization of the monolith by UV irradiation, or incorporated to the polymerization mixture (ex situ). The influence of the AgNP concentration on the morphological and chromatographic properties of the polymer matrix was investigated, and both the in situ and ex situ approaches were comparatively discussed. The morphology of the monoliths was characterized by electron microscopic techniques, and their electrochromatographic performance was also evaluated with test mixtures of neutral compounds (sterols, fatty acid methyl esters, tocopherols, and polyaromatic hydrocarbons). 相似文献
26.
A new class of methacrylate monomers containing perfluorocyclobutyl unit was synthesized in multi-steps including crossing-dimerization, demethylation and esterification using commercially available p-substituted phenol, tetrafluoroethylene and methacryloyl chloride as starting materials. These monomers can be polymerized in solution to provide perfluorocyclobutyl-based polymethacrylate, a kind of potential transparent material. 相似文献
27.
Oluwabusola Edetanlen-Elliot 《Tetrahedron letters》2007,48(50):8926-8929
2,4,6-Trichlorophenyl vinyl sulfonate smoothly undergoes intermolecular radical addition under mild initiation conditions mediated by tributyltin hydride and 1-ethylpiperidine hypophosphite (EPHP) to generate a range of functionalised alkyl sulfonamide precursors. This methodology can be used to prepare bifunctional pentafluorophenyl/2,4,6-trichlorophenyl sulfonates in good yields. 相似文献
28.
Jiajing Wang Danxia Chen Zhao Chen Guorong Fan Yutian Wu 《Journal of separation science》2010,33(8):1099-1108
A rapid CEC method with poly(butyl methacrylate‐co‐ethylene dimethacrylate‐co‐[2‐(methacryloyloxy)ethyl] trimethylammonium chloride) monolithic column has been developed for separation and determination of four coumarins (isopimpinelline, bergapten, imperatorin, and osthole) in Fructus cnidii extracts. The effect of polymerization condition including the monomers ratio and the porogens ratio were studied. The mobile‐phase composition, such as the composition of organic solvent, the concentration and pH of buffer, was also optimized. Under the same condition (50% ACN and 50% of a 10 mM sodium dihydrogen phosphate electrolyte at pH 4.95), in contrast to 25 min of analysis time in HPLC and 10 min of analysis time in pCEC, a fast separation of these analytes was achieved in less than 5 min in CEC. Method validation was developed in accordance with the analytical procedures. Intra‐ and interday precisions (RSD) for relative retention time and peak area were less than 1.69 and 4.63%, and LODs were lower than 0.5 μg/mL. Calibration curves of four compounds also showed good linearity (r2>0.995). The mean recoveries ranged between 93.91 and 98.65%. With this CEC system, the quality of F. cnidii extracts from various resources was evaluated by determining the contents of the four coumarins. 相似文献
29.
Films were prepared from mixtures of copolymers of 4-nitro-4'- [N- methylacryloyloxyethyl,N'-ethyl] amino azobenzene with glycidyl methacrylate (chromophore content: 6 mol%) andcopolymers containing anhydride units, which was obtained by the reaction of 4-nitro-4'-[N-hydroxyethyl, N'-ethyl] amino azobenzene with polymethacryloyl chloride (chromophorecontent: 25 mol %). During thermal poling process the anhydride reacts with the epoxygroup and the resulting crosslinked network structure will stabilize the second harmonicgeneration in the poled film. The second harmonic generation of the poled film shows amaximum with the variation of composition, this is presumed to be due to the effects of theincreasing of concentration, orientation order as well as orientation stability of chromophoregroups during crosslinking. 相似文献
30.