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1.
Abstract The temperature dependence of the three elastic constants k ii (i = 1, 2, 3) and the twist viscosity γ1 of two nematic side chain polyacrylates and one comparable low molecular weight compound have been measured by means of the Freedericksz effect. The change from the low to the high molecular liquid crystal causes a change of the ratio k 33/k 11 from greater to less than unity, but the order of magnitude of the elastic constants remains the same. In contrast, the twist viscosity of the polymeric liquid crystal is about 1000 times greater in magnitude than that of a comparable low molecular weight liquid crystal. The activation energy for the viscosity of the polymer differs by a factor 3–4 from that of the low molecular weight liquid crystal. The elastic constants as well as the twist viscosity show a quadratic dependence on the order parameter S over a wide temperature range. 相似文献
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Dipl.‐Chem. Alexander Rupp Dr. Nataliya Roznyatovskaya Dr. Harald Scherer Dr. Witali Beichel Petra Klose Carola Sturm Dr. Anke Hoffmann Dr. Jens Tübke Prof. Dr. Thorsten Koslowski Prof. Dr. Ingo Krossing 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(31):9794-9804
Several, partly new, ionic liquids (ILs) containing imidazolium and ammonium cations as well as the medium‐sized [NTf2]? (0.230 nm3; Tf=CF3SO3?) and the large [Al(hfip)4]? (0.581 nm3; hfip=OC(H)(CF3)2) anions were synthesized and characterized. Their temperature‐dependent viscosities and conductivities between 25 and 80 °C showed typical Vogel–Fulcher–Tammann (VFT) behavior. Ion‐specific self‐diffusion constants were measured at room temperature by pulsed‐gradient stimulated‐echo (PGSTE) NMR experiments. In general, self‐diffusion constants of both cations and anions in [Al(hfip)4]?‐based ILs were higher than in [NTf2]?‐based ILs. Ionicities were calculated from self‐diffusion constants and measured bulk conductivities, and showed that [Al(hfip)4]?‐based ILs yield higher ionicities than their [NTf2]? analogues, the former of which reach values of virtually 100 % in some cases.From these observations it was concluded that [Al(hfip)4]?‐based ILs come close to systems without any interactions, and this hypothesis is underlined with a Hirshfeld analysis. Additionally, a robust, modified Marcus theory quantitatively accounted for the differences between the two anions and yielded a minimum of the activation energy for ion movement at an anion diameter of slightly greater than 1 nm, which fits almost perfectly the size of [Al(hfip)4]?. Shallow Coulomb potential wells are responsible for the high mobility of ILs with such anions. 相似文献
4.
The problem analyzed is the classical non-regularized Hamiltonian formulation of a restricted three body problem under the
influence of Coulomb-interactions. Completing the large literature on Helium-like systems we will consider the motions around
a fixed positive point charge of (i) one negative and one positive point charge as well as the “classical” issue of (ii) two
negative point charges. Thereby, all our considerations deal with arbitrary positive and negative charge values of the mass
particles. Here, we give necessary and sufficient conditions for the existence of genuine equilibria in such systems—recall
that there are none in the usual classical Helium-atom—and analyze their linearized stability. The thus obtained insights
allow us to study the dynamics near such genuine equilibria. 相似文献
5.
采用一种全新的ADP晶体生长方法,使晶体首先恢复其理想外形,实现晶体的全方位生长,从而提高晶体的生长速度.并对所得晶体进行了透过率,激光散射,摇摆曲线测试及热重差热分析,与常规生长方法比较并分析了全方位生长方法的优势. 相似文献
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E. Grünsteidl E. Chuhrina W. M. Scott R. E. Rupp H. M. Ulrich R. Haller S. Lenher und J. E. Smith 《Fresenius' Journal of Analytical Chemistry》1935,100(7-8):313-314
Ohne Zusammenfassung 相似文献
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E. Rupp 《Zeitschrift für Physik A Hadrons and Nuclei》1932,78(11-12):722-727