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41.
This work examines the influence of the amount of silver nanoparticles added to polyacrylonitrile spinning solutions on their rheological properties as well as the structure and properties of the fibers produced. The influence of the amount of silver nanoparticles on the supramolecular structure of nanocomposite polyacrylonitrile precursor fibers, their porosity, as well as thermal and tensile strength properties was determined. The distribution of the nano‐ additive in fiber cross‐sections and on the surface was estimated. It was found that the addition of silver nanoparticles to polyacrylonitrile precursor fibers in an amount of up to 1.5% does not cause a decrease in the susceptibility of the fiber matter to deformation at the drawing stage. The produced fibers were characterized by an increased total volume of pores of 0.35 cm3/g and tenacity of more than 34 cN/tex. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
42.
Mikołajczyk M Krysiak JA Midura WH Wieczorek MW Rózycka-Sokołowska E 《The Journal of organic chemistry》2006,71(23):8818-8823
A new one-pot synthesis of heterocyclic and carbocyclic vinyl sulfoxides has been developed which involves reaction of alpha-phosphorylvinyl sulfoxides with carbonyl compounds bearing oxygen, nitrogen, and carbon nucleophilic centers. Use of optically active alpha-phosphorylvinyl p-tolyl sulfoxides in this tandem Michael addition/Horner olefination reaction leads to the corresponding optically active cyclic sulfoxides. In this way, a variety of optically active chromene, pyrrolizine, chinoline, and cyclopentene sulfoxides have been efficiently prepared. 相似文献
43.
Treatment of optically active -toluenesulfinamides (1) with thiols (2) in the presence of trifluoroacetic acid was found to give optically active -toluenethio-sulfinates (3) with predominant inversion of configuration. Stereospecificity of this reaction varies from 30 to 80%. Some mechanistic aspects of the reaction are also discussed. 相似文献
44.
J. Omelańczuk P. Kielbasiński J. Michalski J. Mikołajczak M. Mikołajczyk A. Skowrońska 《Tetrahedron》1975,31(22):2809-2814
The reaction of acyclic oxophosphoranesulphenyl chlorides, with phosphorus trichloride has been found to give thiophosphoryl chlorides, and phosphoryl oxychloride—the products of the exclusive deoxygenation of sulphenyl chloride. Optically active phosphonochloridothionates and phosphorochloridothionates in a high state of optical purity have been obtained with inversion of configuration from optically active sulphenyl chlorides and phosphorus trichloride. It has been shown, however, that cyclic oxophosphoranesulphenyl chlorides undergo simultaneous desulphurisation and deoxygenation when treated with phosphorus trichloride. Using cis- and trans-isomers of 2-chlorothio-4-methyl-1,3,2-dioxaphosphorinan-2-one it has been demonstrated that deoxygenation is accompanied by inversion, whereas desulphurisation occurs with retention at phosphorus. The mechanism of the title reaction is discussed. 相似文献
45.
The tittle reagent, (+)-(S)-1, was prepared from (+)-(S)s-α-diethoxy-phosphorylethyl p-tolyl sulfoxide 2 by phenylselenylation-deselenylation procedure. Its reactivity was demonstrated by diastereoselective Michael addition of ethanethiol giving rise to 3, tandem Michael addition/intramolecular Horner--Wittig reaction with 2-formyl pyrrole leading to the corresponding pyrrolizine sulfoxide 5 and cycloaddition with cyclopentadiene affording the diastereomeric adducts 6. The steric course of the Diels-Alder reaction is briefly discussed. 相似文献
46.
An effective synthesis of 1,4-dicarbonyl systems involving the Horner—Wittig reaction of α-phosphoryl sulphides with the half-protected 1,3-dicarbonyl compounds followed by hydrolysis of the vinyl sulphides formed is described. The total synthesis of dihydrojasmone and methylenomycin B employing this approach is reported. 相似文献
47.
Mikołaj Donten Mateusz L. Donten Zbigniew Stojek Kazimierz Wikiel 《Journal of Solid State Electrochemistry》2006,10(5):288-292
This work presents the application of alkanethiols for selectively masking the main surface of copper-seed-layer-covered silicon
wafer, as used for the microprocessor production. The target of the investigation was to deposit copper only in the trenches
and vias (channels of various shape) of micrometer size and not over the entire surface as in the presently used methods.
The procedure developed starts with filling the trenches and vias with water, which is followed by dipping the wafers in a
hexane solution containing dissolved dodekanetiol. Alkanetiol adsorbs and self-organizes on copper not protected with water
and blocks the electroreduction of copper ions from the bath. The trenches and vias are free from adsorbed alkanetiols due
to their very limited solubility in water. The surface-blocking process works very well and may effectively simplify the copper
electrodeposition for microelectronic applications. The selective electrodeposition of copper accomplished by the proposed
method significantly reduces the problems associated with the removal of excess of copper from the processed circuit elements. 相似文献
48.
Lefèvre R Goffman MF Derycke V Miko C Forró L Bourgoin JP Hesto P 《Physical review letters》2005,95(18):185504
We report a method for probing electromechanical properties of multiwalled carbon nanotubes (CNTs). This method is based on atomic force microscopy measurements on a doubly clamped suspended CNT electrostatically deflected by a gate electrode. We measure the maximum deflection as a function of the applied gate voltage. Data from different CNTs scale into an universal curve within the experimental accuracy, in agreement with a continuum model prediction. This method and the general validity of the scaling law constitute a very useful tool for designing actuators and in general conducting nanowire-based nanoelectromechanical systems. 相似文献
49.
50.
The synthesis of enantiomeric phytoprostane B1 type II methyl esters has been accomplished in approximately 30% overall yield via two basic transformations starting from 3-[(dimethoxyphosphoryl)methyl]cyclopentenone as a key reagent. They include ethylation of the ring C(2) carbon and a Horner olefination reaction using the phosphonate moiety at C(3). The novel components of the Horner reaction, the enantiomeric methyl 9-formyl-9-hydroxynanoates, were easily prepared from racemic methyl 9-hydroxy-10-undecenoate via asymmetric Sharpless epoxidation (kinetic resolution) followed by ozonolysis. 相似文献