共查询到20条相似文献,搜索用时 93 毫秒
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Michael V. Sefton Edward W. Merill 《Journal of polymer science. Part A, Polymer chemistry》1976,14(8):1829-1838
Swelling in chloroform resulted in delamination of surface-hydroxylated styrene-butadiene-styrene block copolymers, with the formation of three fractions: crosslinked gel, reacted sol, and unreacted chloroform-soluble material. From the relative weights of these fractions, the depth of penetration of the reaction and the shape of the reaction front were determined. The weight of the gel fraction gave directly an estimate of the depth of penetration, λx which decreased with increasing film thickness. This was attributed to the increased amount of reacted polymer being noncrosslinked material (sol) in the interior compared to the 100% crosslinked nature of the surface region and to a reduction in the penetration of the reaction front resulting from the effect of stress transfer in lowering the permeation rate of peracetic acid. Comparison of the depth of penetration estimates λx and λs determined from the weight of the unreacted polymer demonstrated that, for the conditions used, the reaction front is quite broad. (For example, at 40°C, in 71% acetic acid for 80 min, the fully crosslinked portion is 15 μm thick and the partially reacted region extends for another 8.5 μm.) The combined influences of the increase in penetration of the reactants in the polymer and the relief of stress secondary to this increase in penetration were reflected in the time dependence of the depths of penetration λx and λs. 相似文献
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D. R. Deans 《Chromatographia》1968,1(9-10):418-418
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By means of thin-layer ion-exchange chromatography, human hemoglobins A, S, and C in various combinations can be distinctly separated. Also, hemoglobin F can be separated from the A, S, and C components of cord blood samples from infants and in adult blood samples with a relatively high percentage of F (15% or more). The procedure uses CM-cellulose and solutions of Tris-HCl, NaCl, and KCN. A 0.3-mg sample in 5-10 mul of solvent is required. Development can be completed in 30-40 min. 相似文献
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A short and efficient synthesis of 2-acetonylpyranonaphthoquinones (13 and 14) starting from Michael adduct 5 is described. 相似文献
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Daisuke Uemura Katsuhiro Ueda Yoshimasa Hirata Hideo Naoki Takashi Iwashita 《Tetrahedron letters》1981,22(29):2781-2784
The full structure of palytoxin, a potent coelenterate toxin, is reported. 相似文献