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191.
ABSTRACTA homologous series of new chiral liquid crystal compounds, MnBEB (n = 4–10), was prepared by covalently linking a chiral (–)-menthyl with biphenyl-benzoate via a dicarboxylic spacer of varying length and parity. A combination of analysis methods, such as FT-IR, 1H NMR spectra, differential scanning calorimetry (DSC), polarised optical microscopy (POM) and X-ray diffraction was carried out to systematically investigate their phase structures and phase transition behaviours. The length and parity of the flexible spacers has a profound influence on the Tm and Tc and a modest odd-even effect is observed for the chiral liquid crystal compounds MnBEB. Only compound M4BEB developed an N* phase with selectively reflection on heating and a blue phase on cooling process. In addition, increasing the length of the flexible spacers tends to narrow the temperature range of the N* phase and widen the smectic phase, moreover, the pitch becomes longer with the spacer increases. 相似文献
192.
S. Munavalli R. K. Rohrbaugh G. W. Wagner H. D. Durst F. R. Longo 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1635-1643
Treatment of norbornene with trifluoromethylsulfenyl chloride at ?80°C furnishes, in addition to trifluoromethylthionortricyclane, four isomeric (chloro) (trifluoromethylthio)-norbornanes and bis-(2, 6-trifluoromethylthio)norbornane. The probable mechanism of the formation of the various compounds via free radical intermediates and their mass spectral characterization are described in this communication. 相似文献
193.
The propagation of rough and smooth wall pre-existing turbulent fluid fractures is investigated. The laminar fluid fracture is included as a special case for comparison. Lubrication theory is assumed to apply in the fracture and turbulence is introduced through the wall shear stress. The Perkins–Kern–Nordgren approximation is made in which the fluid pressure is proportional to the half-width of the fracture. The fracture half-width satisfies a non-linear diffusion equation. By using a linear combination of the Lie point symmetries of the non-linear diffusion equation a group invariant solution for the fracture length, volume and half-width is derived. The evolution of the length, half-width and mean flow velocity is analysed for a range of working conditions at the fracture entry. It is found that the mean flow velocity increases approximately linearly along the fracture. 相似文献
194.
2-(1-Naphthylacetyl)ethyl acrylate (NAEA) was synthesized by esterification of 1-naphthylacetic acid (NAA) and 2-hydroxyethyl acrylate (HEA) and then polymerized to obtain the polymer-bound auxin NAA. The resulting polymer is potentially useful as a plant growth regulator through hydrolytic release of NAA. Copolymers of NAEA with hydrophilic comonomers were prepared by solution polymerization. The copolymer compositions were determined from elemental analysis, 13C-NMR, and UV spectroscopy. The copolymer microstructure was predicted from the reactivity ratios in order to investigate the influence on the behavior of controlled release. These model structures will be utilized for assessment of structure/hydrolysis relationships in a subsequent paper. 相似文献
195.
Dr. Papri Sutar Dr. Vasudeva Rao Bakuru Pooja Yadav Subhajit Laha Dr. Suresh Babu Kalidindi Prof. Dr. Tapas Kumar Maji 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(10):3268-3272
The composite hydrogel of a nanoscale metal–organic framework (NMOF) and nanoclay has emerged as a new soft-material with advanced properties and applications. Herein, we report a facile synthesis of a hydrogel nanocomposite by charge-assisted self-assembly of Pd@ZIF-8 nanoparticles with Laponite® nanoclay which coat the surface of Pd@ZIF-8 nanoparticles. Such surface coating significantly enhanced the thermal stability of the ZIF-8 compared to the pristine framework. Further, the Pd@ZIF-8+LP hydrogel nanocomposite shows better size-selective catalytic hydrogenation of olefins than Pd@ZIF-8 nanoparticles based on selective diffusion of the substrate. 相似文献
196.
197.
3,4-Diaroylfuroxans 1 react with various dipolarophiles 3 under microwave activation to afford the cycloadduct 4 instead of the expected isoxazole 5 in good yields in the absence of solvent. 相似文献
198.
N. Ouerfelli 《Physics and Chemistry of Liquids》2018,56(3):412-415
Expressions of Redlich–Kister (RK) excess function using polynomials on difference of molar composition are used. Calculated values of excess properties from experimental values are well presented in some curves as a function of mole fraction (x2) of the second pure component of the studied binary liquid mixture. Nevertheless, the authors presented values of adjustable parameters, not for the polynomial of the popular RK equation (i.e. vs. x2–x1), but for globally the excess property YE as an overall three degree polynomial on (x2) including implicitly the molar fraction product (x1·x2) in their nonlinear regression, which can then induces some readers to probable confusion. 相似文献
199.
Polystyrene-supported 2-azidoethyl phenyl selenide and 3-azidopropyl phenyl selenide reagents have been developed and applied to the traceless solid-phase organic synthesis of 1-vinyl- and 1-allyl-1,2,3-triazoles by CuI-mediated azide–alkyne cycloadditions and subsequent cleavage from the polymer support through oxidation–elimination reaction with 30% hydrogen peroxide. The advantages of this method include straightforward operation, good yield and purity of the products, and good stability and lack of odor for the reagents. 相似文献
200.
Eduard Feireisl 《偏微分方程通讯》2019,44(3):271-278
We show the weak–strong uniqueness property for the compressible Navier–Stokes system with general non-monotone pressure law. A weak solution coincides with the strong solution emanating from the same initial data as long as the latter solution exists. 相似文献