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细乳液聚合法制备磁性复合微球及其表征 总被引:16,自引:7,他引:16
在制备超细Fe3O4 磁性粒子的基础上 ,以 3种低分子量聚合物Disperbyk 1 0 6、Disperbyk 1 0 8和Disperbyk 1 1 1为Fe3O4 微粒在单体相中的分散稳定剂 ,采用细乳液聚合法制备了平均粒径为 3 40nm的PS Fe3O4 磁性复合微球 .详细研究了分散剂种类对细乳液聚合制备磁性复合微球的影响 ,并采用XRD、TGA和TEM等手段对磁性复合微球的形态、结构及磁响应性等进行了表征 .实验结果证明分散剂的选择对磁性复合微球的成功制备起着至关重要的作用 ,兼具酸性和碱性功能基的分散剂Disperbyk 1 0 6具有更好的分散和稳定效果 .TEM结果表明 ,所制备的复合微球具有一些缺陷 ,而缺陷处往往是Fe3O4 磁性粒子聚集的地方 相似文献
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分散聚合法合成磁性高分子微球 总被引:12,自引:1,他引:12
在磁流体存在下,以聚乙二醇(w=4000)为分散剂,乙醇/水为分散介质,进行苯乙烯—丙烯酸—二乙烯基苯的分散聚合,合成具有磁核的聚苯乙烯微球。磁性聚苯乙烯微球的红外光谱显示出磁性氧化铁的特征吸收峰(580cm~(-1)),微球内部磁性氧化铁含量可控制,500-4000μg/g之间。考察了磁流体、聚乙二醇、分散介质和丙烯酸对微球磁响应性和粒径的影响。合成了粒径为1-10μm的磁性高分子微球。 相似文献
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磁性聚苯乙烯微球的制备与性能研究 总被引:5,自引:0,他引:5
以聚苯乙烯和二氯甲烷为油相,十二烷基苯磺酸钠 (SDBS) 为表面活性剂,采用溶剂挥发法制备了磁性聚苯乙烯微球.研究了温度、搅拌速度、Fe3O4用量和pH值等操作因素对磁性微球的形貌、粒径和磁学性能的影响.结果表明,采用溶剂挥发法可以制备含有磁性颗粒Fe3O4的磁性微球.磁性微球的粒径,磁响应性能与制备磁性微球的温度、搅拌速率、水溶液的pH值、磁粉用量等操作参数有关.综合考虑微球的粒径大小、分布以及磁响应性得出,在本实验体系中,20℃的操作温度、1000r/min的搅拌速率、弱碱性的水相溶液以及1.5:10 (磁粉:聚苯乙烯) 的比例是制备磁性微球的适宜操作条件. 相似文献
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Fe3O4/P(St—AA)核—壳复合微球的制备和表征 总被引:8,自引:1,他引:8
以磁性氧化铁胶体粒子为种子,运用分散聚合法,制备出具有磁响应性的Fe3O4/P(St-AA)核-壳复合微球,考察了复合微球的形态及结构,测定了复合微球的粒径和磁响应性,研究了分散介质,引发剂,聚合单体和种子粒子等因素对复合微球形成的影响。 相似文献
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含羟基磁性高分子微球的合成及表征 总被引:14,自引:0,他引:14
采用分散聚合法,以Fe3O4粉末为磁核,苯乙烯-甲基丙烯酸羟乙酯共聚物为高分子壳层、合成了带羟基的磁性复合高分子微球。Fe3O4与苯乙烯等油溶性单体亲合性差,有聚乙二醇溶液处理磁粉增强其表面亲水、亲油性。控制合成条件,成可以得到粒径为50-500μmFe3O4含量为0.5-2.5%的磁性微球。 相似文献
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Rolf W. Saalfrank Norbert Löw Bernhard Demleitner Dietmar Stalke Markus Teichert 《Chemistry (Weinheim an der Bergstrasse, Germany)》1998,4(7):1305-1311
Efficacious metal control of self-assembly of dialkylketipinate dianions leads to completely different supramolecular assemblies. The structures of grid 1 , double-decker 2 , triple-decker 3 , and metalla-spherand 4 were characterized by X-ray crystallographic analyses or by NMR spectroscopy. 相似文献
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C. Peter Sebastian Constanze Fehse J. Paul Attfield Sudhindra Rayaprol Rainer Pöttgen 《Journal of solid state chemistry》2006,179(8):2376-2385
The rare earth-silver-stannides YAgSn, TmAgSn, and LuAgSn were synthesized from the elements by arc-melting and subsequent annealing. The three stannides were investigated by X-ray powder and single-crystal diffraction: NdPtSb type, P63mc, Z=2, a=468.3(1), pm, wR2=0.0343, 353 F2 values, 12 variables for YAgSn, and ZrNiAl type, P6¯2 m, a=726.4(2), , wR2=0.0399, 659 F2 values, 15 variables for TmAgSn, and a=723.8(2), , wR2=0.0674, 364 F2 values, 15 variables for LuAgSn. Besides conventional laboratory X-ray data with monochromatized Mo radiation, the structures were also refined on the basis of synchrotron data with , in order to clarify the silver-tin ordering more precisely. YAgSn has puckered, two-dimensional [AgSn] networks with Ag-Sn distances of 278 pm, while the [AgSn] networks of TmAgSn and LuAgSn are three-dimensional with Ag-Sn distances of 279 and 284 pm for LuAgSn. Susceptibility measurements indicate Pauli paramagnetism for YAgSn and LuAgSn. TmAgSn is a Curie-Weiss paramagnet with an experimental magnetic moment of 7.2 μB/Tm. No magnetic ordering is evident down to 2 K. The local environments of the tin sites in these compounds were characterized by 119Sn Mössbauer spectroscopy and solid-state NMR (in YAgSn and LuAgSn), confirming the tin site multiplicities proposed from the structure solutions and the absence of Sn/Ag site disordering. Mössbauer quadrupolar splittings were found in good agreement with calculated electric field gradients predicted quantum chemically by the WIEN2k code. Furthermore, an excellent correlation was found between experimental 119Sn nuclear magnetic shielding anisotropies (determined via MAS-NMR) and calculated electric field gradients. Electronic structure calculations predict metallic properties with strong Ag-Sn bonds and also significant Ag-Ag bonding in LuAgSn. 相似文献
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A new protocol for the Ullmann-type arylation process of different aromatic heterocycles without any transition-metal catalyst, implying the use of a combination of an excess of potassium hydroxide and dimethyl sulfoxide, is described. The reaction can be performed between a broad range of starting nucleophiles including phenol, alcohols, amines, nitrogen-containing five-membered systems such as pyrazoles, imidazoles, and indoles, and amides with haloarenes, iodide and bromide derivatives giving the best results, the possible pathway involving the in situ generation of the corresponding benzyne intermediate. When the reaction was performed with 2-iodoaniline and either carboxamides or isothiocyanato derivatives, the corresponding benzoazole derivatives were obtained. 相似文献
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Saalfrank RW Prakash R Maid H Hampel F Heinemann FW Trautwein AX Böttger LH 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(9):2428-2433
Heptanuclear metal-centered, six-membered, mixed-valent, heterometallic wheels 1-3 of iron, manganese, and indium were prepared in a one-pot reaction from N-benzyldiethanolamine (H2L(1)), cesium carbonate, [PPh4]2[MnCl4], and FeCl3 or InCl3. All three complexes were characterized by the combination of elemental analysis, FAB mass spectroscopy, X-ray diffraction and cyclic voltammetry and in the case of 1 additionally by M?ssbauer spectroscopy. In 1, four Mn(II) ions in the periphery are arranged in pairs alternating with one Fe(III) ion each, with an Fe(III) ion located in the center. In 2, three Mn(II) ions alternate with three In(III) ions, whereas in 3, four In(III) ions are arranged in pairs and alternate with one Mn(II) ion each. In 2 and 3 an Mn(II) ion is encapsulated in the center. 相似文献
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Ab initio molecular orbital methods at the CBS-QB3 level of theory have been used to study the structure and gas-phase stability of various tautomers and rotamers of N-hydroxyurea, N-hydroxythiourea, and N-hydroxysilaurea, their anions and protonated forms. The geometries of N-hydroxyurea, N-hydroxythiourea, and N-hydroxysilaurea, their anions and cations were optimized at the Becke3LYP/CBSB7 level of theory. For all compounds studied, the amidic form is computed to be substantially more stable than the iminolic tautomer. N-Hydroxyurea and its thio and sila derivatives are computed to behave as Nacids in the gas phase. These compounds are in gas-phase weak acids with a calculated acidity of about 1425 to 1355 kJ-mol–1. Basicities increase in the order: N-hydroxyurea < N-hydroxythiourea < N-hydroxysilaurea. The most stable protonated structures are represented by several isomers with almost equal stability. Thus, in the N-hydroxyurea, N-hydroxythiourea, and N-hydroxysilaurea, both protonation at the double bonded (C=O, C=S and Si=O) oxygen and sulfur atoms, as well as the protonation at the N(H)OH nitrogen basic center is equally probable. The experimental pK
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value (10.6) of N-hydroxyurea and the computed value (9.7) for its monohydrated complex with the specifically hydrogen-bonded water molecule to the ionizable OH group are in a good agreement. The experimental partition coefficient of N-hydroxyurea is best reproduced by the Alog Ps method. The formation of nitroxide radical in the reaction of N-hydroxyurea and its sulfur and silicon substituted derivatives with the phenol radical is an exothermic process. Thus, the \bondN(H)OH moiety of these compounds may quench the structurally related tyrosyl radicals in the active site of ribonucleotide reductase. 相似文献
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High quality SCF-MO calculations are reported for the title molecules, including geometry optimization. One-electron properties are presented and discussed, and relative stabilities of (HOS, HSO) and (FOS, FSO) compared. Little experimental geometric data are available at present, but the calculated and experimental geometries of HO2 agree well. 相似文献
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V. V. Gavrilenko L. A. Chekulaeva I. A. Savitskaya I. A. Garbuzova 《Russian Chemical Bulletin》1992,41(11):1957-1959
A convenient and practical method is proposed for the synthesis of lanthanide and yttrium alkoxides. The method involves dissolving the metals or their hydrides in a solution of dry HCl in the corresponding alcohol, with subsequent dehalogenation of the LnCl3 solution by an equivalent amount of alkali metal (Na, Li), The rareearth alkoxides are easily converted into acetylacetonates Ln(acac)3 by the action of acetylacetone.A. N. Nesmeyanov Institute of Elementoorganic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2490–2493, November, 1992. 相似文献
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Miwa H Makarova EA Ishii K Luk'yanets EA Kobayashi N 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(5):1082-1090
Metal-free tetraazachlorin (TAC), -bacteriochlorin (TAB), and -isobacteriochlorin (TAiB) were characterized by electronic absorption, magnetic circular dichroism (MCD), fluorescence, and time-resolved ESR (TR-ESR) spectroscopy, and by cyclic voltammetry. The results are compared with those of metal-free tetraazaporphyrin (TAP). The potential difference DeltaE between the first oxidation and reduction couples decreases in the order TAP>TAiB>TAC>TAB. The splitting of both the Q and Soret bands decreases in the order TAB>TAC>TAP>TAiB. Corresponding to the split absorption bands, MCD spectra show a minus-to-plus pattern with increasing energy in both the Q and Soret regions, which suggests that the energy difference between the HOMO and second HOMO is larger than that between the LUMO and second LUMO. These spectroscopic properties and redox potentials were reproduced by molecular orbital calculations using the ZINDO/S Hamiltonian. The fluorescence quantum yields of the reduced species are much smaller than that of TAP. The zero-field splitting (ZFS) parameters D and E of the excited triplet states (T1) of these species decrease and increase, respectively, on going from TAP to TAC and further to TAB. The D and E values of TAiB are larger than those of the other species. The results are supported by the absence of interaction between the spin over reduced pyrrole moieties of the HOMO and over the LUMO, and by calculations of ZFS under a half-point-charge approximation. 相似文献
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R. V. Tsyshevsky B. Nguen Van A. G. Shamov G. M. Khrapovskii 《Russian Journal of General Chemistry》2013,83(10):1823-1839
The geometry of cation-radicals and anion-radicals of nitromethane, dimethylnitramine, and ethyl nitrate have been computed by means of modern quantum-chemical methods. Their electron affinities and ionization potentials have been determined. The validity of the results has been confirmed by comparison with the experiment. 相似文献