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排序方式: 共有131条查询结果,搜索用时 15 毫秒
81.
Frank Wiesbrock Richard Hoogenboom Caroline H. Abeln Ulrich S. Schubert 《Macromolecular rapid communications》2004,25(22):1895-1899
Summary: The ring‐opening cationic polymerization of 2‐ethyl‐2‐oxazoline was performed in a single‐mode microwave reactor as the first example of a microwave‐assisted living polymerization. The observed increase in reaction rates by a factor of 350 (6 h → 1 min) in the range from 80 to 190 °C could be attributed solely to a temperature effect as was clearly shown by control experiments and the determined activation energy. Because of the homogenous microwave irradiation, the polymerization could be performed in bulk or with drastically reduced solvent ratios (green chemistry).
82.
The synthesis, characterization and application of lyotropic precursor polymers for polyimides, poly(amic ethyl ester)s (PAE) are presented. By the use of non-coplanar and para-linked monomers, rigid-rod PAEs are synthesized in a typical polycondensation reaction yielding liquid crystalline solutions at concentrations of 30-40 wt% in NMP at 100°C. These lyotropic solutions permit for the first time the fabrication of orientation PAE layers by shear which are thermally converted to the corresponding polyimide. The bulk orientation in the thin films is characterized by spectroscopic methods. In addition the lyotropic solution is spun into fibers in a dry-jet wet spinning process. The obtained fiber orientation is characterized by tensile tests and wide angle X-ray scattering. 相似文献
83.
84.
Clemens Ebner Thomas Bodner Franz Stelzer Frank Wiesbrock 《Macromolecular rapid communications》2011,32(3):254-288
The application of microwave irradiation in polymer syntheses and modifications is of continuously growing interest and has received significant international interest since the beginning of the millennium. Preceded by a review that was published 6 years ago, the present paper summarizes the most recent trends in this research area. Radical as well as step‐growth and ring‐opening polymerizations will be addressed; furthermore, the evolution from microwave‐assisted polymerizations to microwave‐assisted material fabrication will be described on the examples of polymeranalogous reactions, polymer/metal composites and bio‐based materials.
85.
In this paper we use the approach introduced in (Goerss et al., Ann Math 162(2):777–822, 2005) in order to analyze the homotopy groups of $L_{K(2)}V(0)$ , the mod- $3$ Moore spectrum $V(0)$ localized with respect to Morava $K$ -theory $K(2)$ . These homotopy groups have already been calculated by Shimomura (J Math Soc Japan 52(1): 65–90, 2000). The results are very complicated so that an independent verification via an alternative approach is of interest. In fact, we end up with a result which is more precise and also differs in some of its details from that of Shimomura (J Math Soc Japan 52(1): 65–90, 2000). An additional bonus of our approach is that it breaks up the result into smaller and more digestible chunks which are related to the $K(2)$ -localization of the spectrum $TMF$ of topological modular forms and related spectra. Even more, the Adams–Novikov differentials for $L_{K(2)}V(0)$ can be read off from those for $TMF$ . 相似文献
86.
Andrew M. Kelly Angela Hecke Bianca Wirnsberger Frank Wiesbrock 《Macromolecular rapid communications》2011,32(22):1815-1819
A 32‐membered library of poly(2‐oxazoline)‐based hydrogels of the composition p EtOx m‐p PhOx n‐p PBO q (m/n = 150/0, 100/50, 50/100, and 0/150; q = 1.5–30) was prepared from 2‐ethyl‐ ( EtOx ), 2‐phenyl‐2‐oxazoline ( PhOx ), and phenylene‐1,3‐bis‐(2‐oxazoline) ( PBO ). The polymerizations were performed from ground monomer mixtures at 140 °C in a single‐mode microwave reactor in reaction times as short as 1 h. Purified hydrogels, containing no residual monomers, were obtained in yields of 95% or higher. Acid‐mediated hydrolysis rates as well as swelling degrees of the hydrogels were adjustable over a broad range; swelling degrees in water/ethanol/dichloromethane ranged from 0 to 13.8/11.7/20.0. The hydrogels could incorporate organic molecules according to in situ or post‐synthetic routines. Post‐synthetic routines enabled for the preparation of hydrogels from which the incorporated compounds were only released through diffusion processes if the solvent was changed or through hydrogel degradation if the pH was lowered. 相似文献
87.
Milanov AP Seidel RW Barreca D Gasparotto A Winter M Feydt J Irsen S Becker HW Devi A 《Dalton transactions (Cambridge, England : 2003)》2011,40(1):62-78
A series of malonate complexes of dysprosium were synthesized as potential metalorganic precursors for Dy containing oxide thin films using chemical vapor deposition (CVD) related techniques. The steric bulkiness of the dialkylmalonato ligand employed was systematically varied and its influence on the resulting structural and physico-chemical properties that is relevant for MOCVD was studied. Single crystal X-ray diffraction analysis revealed that the five homoleptic tris-malonato Dy complexes (1-5) are dimers with distorted square-face bicapped trigonal-prismatic geometry and a coordination number of eight. In an attempt to decrease the nuclearity and increase the solubility of the complexes in various solvents, the focus was to react these dimeric complexes with Lewis bases such as 2,2'-biypridyl and pyridine (6-9). This resulted in monomeric tris-malonato mono Lewis base adduct complexes with improved thermal properties. Finally considering the ease of synthesis, the monomeric nature and promising thermal characteristics, the silymalonate adduct complex [Dy(dsml)(3)bipy] (8) was selected as single source precursor for growing DySi(x)O(y) thin films by liquid injection metalorganic chemical vapor deposition (LI-MOCVD) process. The as-deposited films were analyzed for their morphology and composition by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, Rutherford backscattering (RBS) analysis and X-ray photoelectron spectroscopy. 相似文献
88.
Humberto Rodriguez-Alvarez Roland Mainz Bjoern Marsen Hans-Werner Schock 《Journal of solid state chemistry》2010,183(4):803-7196
We monitor the recrystallization of Cu-poor CuInS2 thin films assisted by pure Cu or pure Ag by means of real-time synchrotron-based polychromatic X-ray diffraction. In both cases a new microstructure is formed accompanied by an increase in grain size. In the case of Cu, the onset temperature of the thin-film recrystallization is higher than 370 °C. In the case of Ag, the thin-film recrystallization comes to an end at 270 °C. The Ag-assisted recrystallization occurs in the presence of the body-centered cubic β-Ag2S phase. We find that domain growth and diffusion of silver into the film occur simultaneously. 相似文献
89.
Starting with a conformal Quantum Field Theory on the real line, we show that the dual net is still conformal with respect
to a new representation of the M?bius group. We infer from this that every conformal net is normal and conormal, namely the
local von Neumann algebra associated with an interval coincides with its double relative commutant inside the local von Neumann
algebra associated with any larger interval. The net and the dual net give together rise to an infinite dimensional symmetry
group, of which we study a class of positive energy irreducible representations. We mention how superselection sectors extend
to the dual net and we illustrate by examples how, in general, this process generates solitonic sectors. We describe the
free theories associated with the lowest weight n representations of , showing that they violate 3-regularity for $n > 2. When n≥ 2, we obtain examples of non M?bius-covariant sectors of a 3-regular (non 4-regular) net.
Received: 19 March 1997 / Accepted: 1 July 1997 相似文献
90.
Hans-Werner Wiesbrock 《Communications in Mathematical Physics》1992,145(1):17-42
We present a construction of the closed string algebra in terms of Gaussian processes and crossed products. Also we give a purely functional analytical prove of the sh-Lie-structure. 相似文献