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排序方式: 共有649条查询结果,搜索用时 180 毫秒
1.
Dr. Kyung-Seok Kang Dr. Krishnan A. Iyer Prof. Dr. Jeffrey Pyun 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(35):e202200115
In this concept review, the fundamental and polymerization chemistry of inverse vulcanization for the preparation of statistical and segmented sulfur copolymers, which have been actively developed and advanced in various applications over the past decade is discussed. This concept review delves into a discussion of step-growth polymerization constructs to describe the inverse vulcanization process and discuss prepolymer approaches for the synthesis of segmented sulfur polyurethanes. Furthermore, this concept review discusses the advantages of inverse vulcanization in conjunction with dynamic covalent polymerization and post-polymerization modifications to prepare segmented block copolymers with enhanced thermomechanical and flame retardant properties of these materials. 相似文献
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The synthesis of oligoethylene glycols of defined lengths possessing different end functionalities is described. The utility of these molecules towards the development of a generic membrane anchor is demonstrated. 相似文献
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Santhosh P Gopalan A Vasudevan T 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(7):1427-1439
UV-visible spectroelectrochemical studies on copolymerization of diphenylamine (DPA) with ortho-methoxy aniline (OMA) were carried out for different feed ratios of DPA and OMA using indium tin oxide (ITO)-coated glass as working electrode. The UV-visible spectra show clear dependencies on the molar feed composition of DPA or OMA used in electropolymerization. Derivative cyclic voltabsorptogram (DCVA) was deduced at the wavelengths corresponding to the absorption by the intermediate species and used to confirm the intermediates generated during the electropolymerization. The composition of DPA and OMA in the copolymer for the copolymers synthesized with different molar feed ratios of DPA and OMA was determined by UV-visible spectroscopy. Reactivity ratios of DPA and OMA were deduced by using Fineman-Ross and Kelen-Tudos methods and correlated with spectroelectrochemical results. 相似文献
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Non-empirical SCF and CI calculations are reported for the HN2, free radical in various low-lying electronic states. The nature of the angular and N-N and N-H stretching potential curves of each of these species is investigated, including a study of the dissociative behavior of such states. The ground state is found to be only very slightly bound with respect to NH stretch, in contrast to what is observed for isoelectronic HCO, The vertical electronic spectrum of HN2, appears to be marked by a single long wavelength transition (1.95 eV) from the bent (124°) ‘A’ ground state to the linear 2Π excited species, but at least four other intra-valence and an additional n → 3s Rydberg species are indicated in the 5.5–8.0 eV absorbing region. 相似文献
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P. C. Kalsi A. K. Pandey R. H. Iyer 《Journal of Radioanalytical and Nuclear Chemistry》1995,201(2):165-170
A -spectrometric method has been developed for the assay of uranium in crude UF4, which is used as a secondary source of input material for producing nuclear grade U-metal at natural uranium conversion plants. The method makes use of a NaI (Tl) detector coupled with a multichannel analyzer. The 1 MeV -ray of238U is used for calibration. A method for the fabrication of uniform -assay calibration standards is also suggested, based on the results of this investigation. The calibration standards were prepared by soaking the matrix in uranium solution and then drying the whole material. The amount of238U in the crude UF4 sample was directly estimated by comparing the areas under the 1 MeV -ray peak of known calibration standards with the corresponding areas of the samples to be measured. 100 g each of the standard and the sample were counted. 5 crude UF4 samples were analyzed by this method. The uranium contents in these samples were found to be in the range of 12.2–28.7 g. To compare the -ray spectrometry results with a completely independent method, chemical analysis by potentiometry of all the samples was also done. The -spectrometric results were found to agree within ±18% with the chemical analysis results. 相似文献
10.
Two low-dimensional compounds, KSnAsS(5) and K(2)SnAs(2)S(6), were prepared using liquid polythioarsenate salts, and the results differ from those obtained with the well studied thiophosphate flux. KSnAsS(5) crystallizes in the orthorhombic space group Pbam with cell parameters of a = 8.136(2) A, b = 13.784(4) A, c = 7.428(2) A. KSnAsS(5) features the unusual pyramidal species [AsS(2)(S(2))](3-). K(2)SnAs(2)S(6) crystallizes in the trigonal space group P3 macro with cell parameters a = 6.717(5) A, b = 7.204(8) A, gamma = 120 degrees. The compounds were obtained by controlling the Lewis basicity of the K(2)S/As(2)S(3)/S flux. The optical, thermal, and spectroscopic properties of the compounds are reported. 相似文献