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641.
Inside Back Cover: Formation of Tri‐ and Tetranuclear Titanacycles through Decamethyltitanocene‐Mediated Intermolecular C–C Coupling of Dinitriles (Angew. Chem. Int. Ed. 18/2015) 下载免费PDF全文
642.
Dirk Kuckling Hans-Jürgen Adler Karl-Friedrich Arndt Thomas Wolff Jan Hoffmann Wolf-Joachim Fischer 《Macromolecular Symposia》1999,142(1):111-120
Polymers with temperature dependent degrees of swelling, especially polymers which exhibit lower critical solution temperature (LCST) behaviour in aqueous solutions, are of interest for applications in microsystems. For these applications it is necessary to form and pattern thin films in the μm-range. This has been achieved through photocrosslinking of linear prepolymers. Copolymers based on N-isopropylacrylamide (NIPAAm) were modified with a stilbazolium salt chromophore to yield photocrosslinkable temperature sensitive polymers. The chromophore reacts via a [2+2]-cycloaddition under irradiation, this can be used to crosslink the polymer. The photocrosslinking properties were studied by UV irradiation of thin films and measuring the changes in UV absorption spectra. Through irradiation of thin films through a mask it was possible to obtain patterned networks in the μm-range (20 μm space width and > 50 μm line width). The polymers exhibited LCST behaviour, which was measured using DSC. The resulting patterned networks had temperature dependent swelling properties in aqueous media. 相似文献
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Anke Spannenberg Hans Fuhrmann Perdita Arndt Wolfgang Baumann Rhett Kempe 《Angewandte Chemie (International ed. in English)》1998,37(24):3363-3365
Partial abstraction of apical methyl groups is observed in aminopyridinatoniobium alkyne complexes, as exemplified with the synthesis and characterization of 1 . This results in cationic complex fragments, which facilitate the polymerization of ethylene and in the presence of methylalumoxane the selective dimerization of 1-butene. 相似文献
645.
With homogenous catalysts on the basis of chiral metallocenes and methylaluminoxane it has become possible to polymerize cyclic olefins like cyclobutene, cyclopentene or norbornene. No ring opening reaction occurs. The crystalline polycycloalkenes show extremly high melting points between 400 and 600°C. Copolymers of cyclopentene with propene are amorphous. They have a low molecular weight and glass transition point. On the other hand the glass transition temperature of norbornene/ethene copolymers exceeds 130°C. These copolymers could be used as materials for optical discs and fibers. 相似文献
646.
Andreas Richter Steffen Howitz Dirk Kuckling Katja Kretschmer Karl-Friedrich Arndt 《Macromolecular Symposia》2004,210(1):447-456
This paper describes automatically and electronically controlled valves and microvalves based on smart hydrogels. The operating performance of such devices will be discussed in dependence on various design parameters. Furthermore, it will be shown that hydrogel based valves are showing an outstanding possibility of miniaturization, a leakage free switching behavior up to a pressure drop of 8.4 bar, and a pronounced particle tolerance. 相似文献
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Reactions of Group 4 Metallocenes with Monosubstituted Acetonitriles: Keteniminate Formation versus CC Coupling 下载免费PDF全文
Lisanne Becker Dr. Martin Haehnel Dr. Anke Spannenberg Dr. Perdita Arndt Dr. Uwe Rosenthal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(8):3242-3248
The reactions of the Group 4 metallocene dichlorides [Cp′2MCl2] ( 1 a : M=Ti, Cp′=Cp*=η5‐pentamethylcyclopentadienyl, 1 b : M=Zr, Cp′=Cp=η5‐cyclopentadienyl) with lithiated MesCH2?C?N gave [Cp*2TiCl(N=C=C(HMes))] ( 3 ; Mes=mesityl) in the case of 1 a . For compound 1 b , a nitrile–nitrile coupling resulted in a five‐membered bridge in 4 . The reaction of the metallocene alkyne complex [Cp*2Zr(η2‐Me3SiC2SiMe3)] ( 2 ) with PhCH2?C?N led in the first step to the unstable product [Cp*2Zr(η2‐Me3SiC2SiMe3)(NC?CH2Ph)] ( 5 ). After the elimination of the alkyne, a mixture of products was formed. By variation of the solvent and the reaction temperature, three compounds were isolated: a diazadiene complex 6 , a bis(keteniminate) complex 7 , and 8 with a keteniminate ligand and a five‐membered metallacycle. Subsequent variation of the Cp ligand and the metal center by using [Cp2Zr] and [Cp*2Ti] with Me3SiC2SiMe3 in the reactions with PhCH2?C?N gave complex mixtures. 相似文献