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71.
The synthesis of well-defined block copolymers from styrene and methyl acrylate via ATRP is discussed in this contribution. Kinetic studies on these block copolymerizations as well as characterization studies were performed to investigate the monomer composition in the respective PS and PMA blocks. MALDI-TOF-MS was performed to clarify the exact number of repeating units of each block and the total number of units in the block copolymer. Block copolymers up to 22 kDa could be analyzed by MALDI-TOF-MS, whereby polymers with PMA as first block showed a large second distribution corresponding to PMA homopolymers. However, SEC demonstrated that only a small amount of homopolymer was present indicating that care needs to be taken with interpreting MALDI-TOF-MS data, which is a qualitative rather than a quantitative technique. 相似文献
72.
Zusammenfassung Das Verhalten von Polypropylen im elektrischen Wechselfeld wurde im Frequenzbereich von 0,15 kHz bis 300 kHz und im Temperaturbereich von –75 C bis +140 C untersucht. Es konnte sowohl ein Tieftemperaturdispersionsgebiet —-Absorption — als auch ein Hochtemperaturdispersionsgebiet —-Absorption — beobachtet werden. Die Untersuchungsergebnisse wurden, um die Breite des Dispersionsgebietes und die zugehörigen -Stufen zu bestimmen, nach demCole-Cole-Kreisbogengesetz analysiert. Aus dem Anstieg der Geraden: logf
max 1/T
K wurden sowohl für die- als auch fur die-Absorption die experimentellen Aktivierungsenergien berechnet. Eine Deutung der Ergebnisse wurde versucht. 相似文献
73.
M. F. Butman V. B. Motalov D. N. Sergeev L. S. Kudin K. W. Krämer 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(5):751-759
The vaporization process of ytterbium di- and tribromide was studied using high-temperature mass spectrometry over the temperature
range of 850 to 1300 K. It was ascertained that, at the early vaporization stages, the vapor contained molecules YbBr3, YbBr2, YbBr, Br2, Yb2Br2, Yb2Br3, Yb2Br4, Yb2Br5, Yb2Br6, and atoms Yb and Br. The partial pressures of all components of saturated vapor were calculated. It was found that vapor
composition reflected the course of the reactions of decomposition of tribromide and disproportionation of dibromide in the
condensed phase. It was concluded that vaporization of di- and tribromide was incongruent at the initial stages; vaporization
of both agents acquired a congruent character with the Yb: Br = 1.0: 1.9±0.2 ratio with time. 相似文献
74.
75.
76.
A mass conservative well‐balanced reconstruction at wet/dry interfaces for the Godunov‐type shallow water model 下载免费PDF全文
This paper presents a novel mass conservative, positivity preserving wetting and drying treatment for Godunov‐type shallow water models with second‐order bed elevation discretization. The novel method allows to compute water depths equal to machine accuracy without any restrictions on the time step or any threshold that defines whether the finite volume cell is considered to be wet or dry. The resulting scheme is second‐order accurate in space and keeps the C‐property condition at fully flooded area and also at the wet/dry interface. For the time integration, a second‐order accurate Runge–Kutta method is used. The method is tested in two well‐known computational benchmarks for which an analytical solution can be derived, a C‐property benchmark and in an additional example where the experimental results are reproduced. Overall, the presented scheme shows very good agreement with the reference solutions. The method can also be used in the discontinuous Galerkin method. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
77.
78.
The numerical properties of the radial part of overlap integrals with the same screening parameters in the form of polynomials
in p = ξR over Slater-type orbitals have been studied and obtained by using three different methods. For that purpose, the characteristics
of auxiliary functions were used first, then Fourier transform convolution theorem, and recurrence relations for the basic
coefficients of A
s
n
l
λ,
n
′
l
′λ were used. The calculations of the radial part of overlap integrals with the same screening parameters were made in the range
1 ≤ n ≤ 75, 1 ≤ n′ ≤ 75, and 10−6 ≤ p.
Received: 18 January 2001 / Accepted: 5 April 2001 / Published online: 27 June 2001 相似文献
79.
80.
Can Coordination‐Driven Supramolecular Self‐Assembly Reactions Be Conducted from Fully Aliphatic Linkers? 下载免费PDF全文
Dr. Mehdi Elsayed Moussa Dr. Sloane Evariste Barbara Krämer Prof. Dr. Régis Réau Prof. Dr. Manfred Scheer Dr. Christophe Lescop 《Angewandte Chemie (International ed. in English)》2018,57(3):795-799
The reaction between a preassembled CuI bimetallic molecular clip with a short intermetallic distance and a series of fully aliphatic cyano‐capped ditopic linkers with increasing lengths was investigated. It is shown that, depending on the length of the ditopic linkers, the rational design of unprecedented supramolecular compact metallacycles containing fully aliphatic walls is possible. The specific preorganized molecular arrangement of the molecular clip used favors stabilizing interlinker London dispersion interactions, which allow, as the length of the linkers increases, the selective formation of discrete compact metallacycles at the expense of 1D coordination polymers. The generalizability of this approach was demonstrated by the reaction of fully aliphatic cyano‐capped linkers with two other types of preassembled CuI bimetallic molecular clips that also had short intermetallic distances. 相似文献