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排序方式: 共有445条查询结果,搜索用时 15 毫秒
441.
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443.
Markus Klapper Yong-Jun Jang Kirsten Bieber Tanja Nemnich Nikolay Nenov Klaus Müllen 《Macromolecular Symposia》2004,213(1):131-146
Nano-sized latex particles as organic supports for metallocenes applied in olefin polymerizations are introduced. The particles are functionalized with nucleophilic surfaces such as polyethylenoxide (PEO), polypropyleneoxide (PPO) or pyridine units allowing an immobilization of the metallocene catalysts via a non-covalent immobilization process. The latices are obtained by emulsion or miniemulsion polymerization with styrene, divinylbenzene as the crosslinker, and either PEO or PPO functionalized styrene or 4-vinylpyridine for surface functionalization. The supported catalysts, e.g. [Me2Si(2MeBenzInd)2ZrCl2/MAO] on PPO containing latices or Cp2ZrMe2/([Ph3C][B(C6F5)4]) on pyridine functionalized materials were tested in ethylene polymerizations. Remarkably, high activities and excellent product morphologies were obtained. The influence of the degree of surface functionalization on activity and productivity was investigated. Furthermore, the fragmentation of the catalyst was studied by electron microscopy using bismuth-labeled latex particles or by fluorescence and confocal fluorescence microscopy using dye-labeled supports. Finally, a self-immobilizing catalyst/monomer system is presented. It is demonstrated that by using PEO-functionalized olefins, the metallocenes were immobilized on the monomers. Subjecting these mixtures to an ethylene copolymerization, again high activities and productivities as well as polyolefin beads with high bulk densities are observed, indicating that an extra supporting process for controlling the product size and shape of the polyolefins is not necessary for these monomers. 相似文献
444.
Kirsten Aarset Quang Shen Hanne Thomassen Alan D. Richardson Kenneth Hedberg 《ChemInform》1999,30(20):no-no
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献
445.
H. Becherer E. Buhrig K. Hein M. John P. Kirsten H. A. Schneider W. Siegel K. Winkler 《Crystal Research and Technology》1978,13(9):1053-1057
Undoped ZnSiP2 crystals grown by different methods (vapour phase transport, solution growth) show in part considerable differences in their physical properties. The connections between growth, quality of the basic materials and the physical properties of ZnSiP2 will be shown. Measurements of Hall effect, resistivity, luminescence and backscattering of protons yielded informations about the perfection and homogenity of the crystals and about the impurities and recombination centres characteristically for the various growth methods. The influence of doping by different elements on the properties of solution grown ZnSiP2 crystals was investigated. 相似文献