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191.
Dan Donescu Liana Fusulan Sever Serban Filip Chiraleu Cristian Petcu 《Journal of Dispersion Science and Technology》2013,34(7):701-715
Abstract The homogeneity ranges of the systems consisting of the monomer (vinyl acetate or vinyl acetate + di-2-ethyl hexil maleate), cosurfactant (ethanol, n-propanol, n-butanol), surfactant (nonylphenol ethoxylate with 25 moles of ethylene oxide) and water were studied. Addition of the more hydrophobic comonomer requires utilization of a more hydrophobic cosurfactant. The increase of surfactant concentration entails the widening of the homogeneity range. The effect of the cosurfactants mentioned is accounted for by the modification of the cluster structure of water. Therefore the refractive indexes and the signals of protons in NMR spectra vary non-linearly with the composition of homogeneous systems. DSC analysis of the systems obtained has come out with two crystallization temperatures of water undercooled to ?60°C in systems of concentrations close to those of organic and aqueous phases. The results plead for the existence of a structure which differs from that of the ideal solutions of the systems studied. 相似文献
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Cristian Carrera‐Figueiras Manuel Aguilar‐Vega 《Journal of Polymer Science.Polymer Physics》2007,45(15):2083-2096
The synthesis, thermal, and gas transport properties of poly(benzophenone isophthalamide), DBF/ISO, poly(benzophenone‐5‐tert‐butylisophthalamide), DBF/TERT, homopolymers, and their copolyamides with different DBF/TERT ratios are reported. The results indicate that the glass transition temperatures of the copolyamides increase as the concentration of DBF/TERT in the polyamide increases. The gas permeability coefficients for DBF/ISO are around 10?2 Barrers for O2 which situates this polymer as a barrier polymer. It was also found that permeability coefficients in all polyamides and copolyamides are independent of pressure for He or decrease slightly particularly with O2, CO2, and N2. It was seen that DBF/TERT is up to 15 times more permeable than DBF/ISO, depending on the gas being considered. This behavior was assigned to the presence of the bulky lateral substituent, the tert‐butyl group, in DBF/TERT and DBF/TERT‐co‐DBF/ISO copolyamides. This bulky substituent increases fractional free volume and interchain spacing; as a consequence, the gas permeability and diffusion coefficients generally increase. The experimental results for the gas permeability coefficients and permselectivity for the copolyamides was well represented by a semilogarithmic mixing rule of the homopolyamides permeability coefficients as a function of their volume fraction. The selectivity of gas pairs, such as He/O2 and He/CO2, decreased slightly with the addition of DBF/TERT. The temperature dependence of permeability for homopolyamides and copolyamides can be described by an Arrhenius type equation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2083–2096, 2007 相似文献
196.
We construct new charged solutions of the Einstein–Maxwell field equations with cosmological constant. These solutions describe the nut-charged generalisation of the higher-dimensional Reissner–Nordström spacetimes. For a negative cosmological constant these solutions are the charged generalizations of the topological nut-charged black hole solutions in higher dimensions. Finally, we discuss the global structure of such solutions and possible applications. 相似文献
197.
Răzvan Şuteu Ciprian I. Raţ Cristian Silvestru Andrada Simion Natalia Candu Vasile I. Pârvulescu Anca Silvestru 《应用有机金属化学》2020,34(4):e5393
The compounds [2-(Me2NCH2)C6H4]2SbL (L = ONO2 ( 2 ), OSO2CF3 ( 3 )) and [PhCH2N(CH2C6H4)2]SbL (L = ONO2 ( 5 ), OSO2CF3 ( 6 )) were prepared by reacting [2-(Me2NCH2)C6H4]2SbCl ( 1 ) and [PhCH2N(CH2C6H4)2]SbCl ( 4 ), respectively, with the appropriate silver(I) salt in a 1:1 molar ratio. The new species 2 – 6 were structurally characterized in solution using multinuclear NMR and in the solid state using infrared spectroscopy. The solid-state structures for compounds 2 , 4 and 6, as well as for the hydrolysis ionic product [{2-(Me2N+HCH2)C6H4}{2-(Me2NCH2)C6H4}SbOH][CF3SO3]− ( 3h ) were determined using single-crystal X-ray diffraction. Medium to strong intramolecular N→ Sb interactions were observed in all these four compounds, thus resulting in hypercoordinated organoantimony(III) species 14-Sb-6 in 2 and 10-Sb-4 in the cation of 3h and in 4 and 6 . Compounds 1 – 6 and the starting amines PhCH2NMe2 and PhCH2N(CH2C6H4Br-2)2 were investigated as catalysts in the Henry (nitroaldol) addition of nitromethane to benzaldehyde. The activity of compounds 1 – 6 resulted as an effect of the cooperation of the positively charged antimony with the negatively charged nitrogen. 相似文献
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Marina Cabrini Sergio Lorenzi Tommaso Pastore Cristian Testa Diego Manfredi Giulio Cattano Flaviana Calignano 《Surface and interface analysis : SIA》2019,51(12):1159-1164
The paper deals with the corrosion resistance in chloride solutions of an AlSi10Mg alloy obtained by laser powder bed fusion (LPBF) process. The potentiodynamic tests were carried out in solutions having different chloride contents. The results emphasize the role of chloride concentration on localized corrosion. The increase of concentration reduces pitting potential. In addition, the influence of the post-processing heat treatment temperature was recognized. Penetrating attacks occurred either on after low temperatures stress relieving or specimens without any treatment, promoted by selective dissolution of the α-Al phase stimulated by galvanic coupling with noble silicon precipitates at the border of the melt pool. Such penetrating morphology was not observed after heat treatments at high temperature. 相似文献
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Beatrice Bartolomei Giuseppe Gentile Dr. Cristian Rosso Dr. Giacomo Filippini Prof. Maurizio Prato 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(65):16062-16070
Phenols ( I ) are extremely relevant chemical functionalities in natural, synthetic and industrial chemistry. Their corresponding electron-rich anions, namely phenolates ( I ), are characterized by interesting physicochemical properties that can be drastically altered upon light excitation. Specifically, phenolates ( I ) become strong reducing agents in the excited state and are able to generate reactive radicals from suitable precursors via single-electron transfer processes. Thus, these species can photochemically trigger strategic bond-forming reactions, including their direct aromatic C−H functionalization. Moreover, substituted phenolate anions can act as photocatalysts to enable synthetically useful organic transformations. An alternative mechanistic manifold is represented by the ability of phenolate derivatives I to form ground state electron donor-acceptor (EDA) complexes with electron-poor radical sources. These complementary scenarios have paved the way for the development of a wide range of relevant organic reactions. In this Minireview, we present the main examples of this research field, and give insight on emerging trends in phenols photocatalysis towards richer organic synthesis. 相似文献