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61.
We have prepared polycrystalline samples of Sr3YCo4O10.56, Sr2.4Ca0.6YCo4O10.54, and Sr3YCo3.76Mn0.24O10.59, and found that these materials show unusual impurity effects on their transport and magnetic properties. A tiny amount of impurities such as Mn or Ca suppresses room-temperature ferromagnetism of Sr3YCo4O10.56. With the suppression, their resistivities and thermopowers are also dramatically changed. We propose that the unusual impurity effects are caused by the suppression of orbital ordering. 相似文献
62.
A family of layered bismuth oxyhalides, LI0.5Bi1.5O2X and LIIBiO2X has been reinvestigated. Formation of X1-type Sillén compounds has been established for LI=Li, Na, LII=Ca, Sr, Ba, and X=Cl, Br, I, but the details of their crystal structures are different. While all LI0.5Bi1.5O2X, CaBiO2Br, and CaBiO2I adopt the disordered tetragonal Nd2O2Te structure, all compounds of LII=Sr and Ba are orthorhombic and isostructural to PbSbO2Cl, due to L/Bi cation ordering. Crystal structures have been determined for CaBiO2I, SrBiO2Br, SrBiO2I, and BaBiO2I. We discuss the factors which determine the occurrence and type of cation ordering in the quaternary bismuth and antimony X1-type oxyhalides. We also predict that more isostructural compounds can be prepared with antimony. 相似文献
63.
Yotaro Morishima Shigeki Nomura Mikiharu Kamachi 《Journal of polymer science. Part A, Polymer chemistry》1994,32(16):3141-3146
3,7-Diethyl- 10-phenylphenothiazine (DEPPT), a phenothiazine derivative whose 3,7- and 10-positions are blocked, was synthesized. Potentiostatic electrolysis of DEPPT in acetonitrile (ACN) in the presence of 0.1M of LiClO4 at 0.7 V (vs. Ag/Ag/Cl) yielded the stable cation radical of DEPPT (DEPPT+·) which was characterized by cyclic voltammetry, UV-visible spectroscopy, and ESR spectrometry. Stable cation radicals of 10-phenylphenothiazine and 3,7-diethyl-10-methylphenothiazine were also prepared. The cationic polymerization of n-butyl vinyl ether was initiated by these cation radicals, including DEPPT·+. The electron transfer mechanism for the initiation step, which we proposed previously, was supported by the fact that DEPPT·+ was capable of initiating the polymerization; dimerization of DEPPT·+ by releasing protons is precluded because 3,7- and 10-positions are all blocked. © 1994 John Wiley & Sons, Inc. 相似文献
64.
65.
阴阳离子型表面活性剂双水相萃取色氨酸衍生物和牛血清白蛋白 总被引:7,自引:0,他引:7
溴化十二烷基三乙胺(C12NE)和十二烷基硫酸钠(SDS)在一定条件下混合可以形成具有清晰界面的两个水相,称为阴阳离子型表面活性剂双水相。作者研究了利用该双水相萃取3种色氨酸衍生物和牛血清白蛋白的可能性.文中采用工作曲线校正扣除表面活性剂背景的影响,萃取结果准确可信。 相似文献
66.
L. Matjka P. Chabanne L. Tighzert J. P. Pascault 《Journal of polymer science. Part A, Polymer chemistry》1994,32(8):1447-1458
The cationic nonlinear polymerization of diglycidyl ether of Bisphenol A (DGEBA) in the presence of a diluent γ-butyrolactone (BL) was initiated by the BF3-4-methoxyaniline (MA) complex. The reaction was studied by size exclusion chromatography, DSC, and dynamic mechanical analysis. Reaction mechanism involves a fast formation of adducts of DGEBA with MA released from the initiator. Formation of spiro orthoesters (S) by reaction of BL with DGEBA and homopolymerization of DGEBA as well as copolymerization with S follow. Gelation occurs at 60°C within a few minutes at conversion of epoxy groups (ξE)c = 0.20–0.45. The networks cured under optimum conditions show high glass transition temperature, Tα = 178°C. The mechanism-structure-property relations are discussed. © 1994 John Wiley & Sons, Inc. 相似文献
67.
对于NO分子轨道的能级次序现有两种不同的说法,不少人根据NO与O_2~+是等电子体,由O_2~+分子的能级次序确定NO分子组态。本文用NO和O_2~(+)从头计算结果以及NO的紫外光电子能谱相结合的方法说明NO的5σ轨道是弱成键轨道,5σ的轨道能稍高于1π轨道能,也就是说NO的能级次序是与N_2分子相同的;NO与O_2~+虽是等电子体,但是能级次序并不相同,因此由O_2~+的能级次序确定NO分子的电子组态是不妥的。 相似文献
68.
J. V. Crivello Daoshen Bi 《Journal of polymer science. Part A, Polymer chemistry》1993,31(12):3109-3119
Silicon-containing epoxide compounds bearing Si ? H groups can be readily prepared in high yields by the regioselective rhodium-catalyzed monohydrosilation of α,ω-dihydrogen functional siloxanes and silanes with vinyl epoxides. The remaining Si ? H groups in these compounds can be further selectively hydrosilated with unsaturated epoxides to give a series of unique ambifunctional monomers containing two different epoxide groups in the same molecule. The photopolymerization of these monomers has been studied using analytical techniques including real time infrared spectroscopy and differential scanning photocalorimetry. On photopolymerization, the new monomers yield interesting networks. © 1993 John Wiley & Sons, Inc. 相似文献
69.
Ordered aggregation of thiol-passivated Au nanoparticles in a diblock copolymer polystyrene-b-poly(methyl methacrylate) has been observed. The morphology of the diblock copolymer/Au-nanocomposite was dependent on the composition of the thiol modifier. For the thiol modifier that does not preferentially interact with one of the blocks, a perpendicular (relative to the substrate) lamellar morphology is maintained. However, for a thiol with a surfactant structure similar to one of the blocks, we observed a parallel lamellar morphology and speculate that the nanoparticles have localized at the microdomain interface. These conclusions are based on transmission electron microscopy, angle-dependent X-ray photoelectron microscopy and tensiometry. These results are consistent with theoretical predictions on the hybrid systems composed of block copolymers and nanoparticles. 相似文献
70.
Hiroji Fukui Mitsuo Sawamoto Toshinobu Higashimura 《Journal of polymer science. Part A, Polymer chemistry》1994,32(14):2699-2708
Telechelic ( 8 ) and end-functionalized four-arm star polymers ( 9 ) were synthesized through the coupling reactions of end-functionalized living poly(isobutyl vinyl ether) ( 5; DP n ~ 10) with the bi-and tetrafunctional silyl enol ethers, H4-nC? [CH2OC6H4C(OSiMe3) = CH2]n ( 3: n = 2; 4: n = 4). The precursor polymers 5 were prepared by living cationic polymerization with functionalized initiators, CH3CH(Cl)OCH2CH2X(6), in conjunction with zinc chloride in methylene chloride at ?15°C. The initiators 6 were obtained by the addition of hydrogen chloride gas to vinyl ethers bearing pendant functional groups X , including acetoxy [? OC(O)CH3], styryl (? OCH2C6H4-p-CH = CH2), and methacryloyl [? OC(O)C(CH3) = CH2]. The coupling reactions with 3 and 4 in methylene chloride at ?15°C for 24 h afforded the end-functionalized multiarmed polymers ( 8 and 9 ) in high yield (>91%), where those with styryl or methacryloyl groups are new multifunctional macromonomers. © 1994 John Wiley & Sons, Inc. 相似文献