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141.
An efficient synthesis of propargylamines via C-H activation catalyzed by copper(I) in ionic liquids
A readily available copper(I) catalyst, in an ionic liquid, can effect three-component coupling of aldehydes, amines and alkynes to generate propargylamines in high yields. 相似文献
142.
Yun‐Hi Kim Seong‐Kuk Ahn Hyung Sun Kim Soon‐Ki Kwon 《Journal of polymer science. Part A, Polymer chemistry》2002,40(23):4288-4296
Two new pyromellitic dianhydrides, 1,4‐bis(4′‐t‐butylphenyl) pyromellitic dianhydride and 1,4‐bis(4′‐trimethylsilylphenyl) pyromellitic dianhydride, were synthesized via Suzuki coupling, oxidation, and dehydration. A series of new organosoluble polyimides were prepared from the obtained pyromellitic dianhydride and various aromatic diamines by the conventional polycondensation reaction followed by chemical imidization, as well as high‐temperature, one‐step polymerization. The structures of the dianhydrides and polymers were identified with various spectroscopies. The inherent viscosities of the resulting polymers were 0.62–1.89 dL/g. The synthesized polyimides showed good solubility in various organic solvents such as N‐methyl‐2‐pyrrolidinone, N,N‐dimethylacetamide, and p‐chlorophenol. These polymers had glass‐transition temperatures of 230–260 °C. Thermogravimetric analysis showed that all the polymers were stable, with 10% weight losses recorded above 490 °C in nitrogen. The polyimide films had good mechanical properties and high oxygen permselectivity to nitrogen. The oxygen permeability coefficient (P) and the permselectivity of oxygen to nitrogen (P/P) of the films were 13–56 barrer and 3.7–5.5, respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4288–4296, 2002 相似文献
143.
A series of polyester-based ionomers containing dimethyl 5-sulfoisophthalate sodium salt (DMSI) with up to 5 mol-% diacid units was synthesized by two-step polycondensation. Furthermore a polylactic acid (PLA) was modified by introducing poly(ethylene-co-methacrylic acid) ionomers with different ion groups, such as Na, Li, and Zn, using the melt blending method. This review examines the effect of the ionic group on the dynamic mechanical properties, melt rheology, crystallization behavior, degradation behavior, and biocompatibility with human dermal cells, as well as the nucleating effect of poly(ethylene-co-methacrylic acid) ionomer in PLA. 相似文献
144.
In a preliminary report1 it was shown that the hydrogen-bond chemical shift, δAB, correlates with the change in enthalpy, δH, in the interaction of chloroform with a series of closely related oxygen and nitrogen bases. In this communication, we report the hydrogen bonding parameters for the interaction in cyclohexane medium between 2,4,6-tri-t-butylphenol and tetrahydrofuran, tetrahydropyran and pyridine, and between 2,6-di-1-adamantyl-4-t-butylphenol and pyridine. There is correlation between the δAB and δAE for the same proton donor (2,4,6-tri-t-butylphenol) and the closely related alicyclic bases, and for the same base (pyridine) and the two closely related sterically hindered phenols. The temperature dependence of the δAB in these systems is also reported. 相似文献
145.
Yeong‐Soon Gal Sung‐Ho Jin Jong‐Wook Park 《Journal of polymer science. Part A, Polymer chemistry》2007,45(23):5679-5685
A new ionic polyacetylene with two aromatic heterocycles (pyridyl and thienyl) was prepared by the activation polymerization of 2‐ethynylpyridine by using 3‐(6‐bromohexyloxy)methylthiophene without any additional initiator or catalyst. The activated acetylenic triple bond of N‐substituted‐2‐ethynylpyridinium bromide, formed at first quaternarization process, was susceptible to linear polymerization. The instrumental analysis data on the polymer structure revealed that the polymer have the conjugated polyene backbone structure with the designed two aromatic heterocycles. The photoluminescence peak is located at 510 nm corresponding to a photon energy of 2.43eV. The electrochemical properties of this ionic polyacetylene were also measured and discussed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5679–5685, 2007 相似文献
146.
Soon Muk Hwang Quang-Viet Nguyen 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(16):2715-2724
Even for the well-studied and ubiquitous species, OH, the current state of theoretical development of broadening theory does not allow extrapolation from low-temperature laboratory measurements to the range of practical combustion devices. We performed a series of experiments at typical combustion conditions to determine the collision broadening of the P1(5) line of the (0,0) band of OH A2Σ+←X2Π transition by Ar in shock-heated H2-O2-Ar mixtures and by air in H2-air flames over a wide range of stoichiometry (φ=0.01-10.0), temperature (T=780-2440 K), and pressure (p=0.7-10.0 atm). The values of the collision width, ΔνC, were acquired by fitting Voigt profiles to the measured spectral line shapes in flames and to the peak absorption coefficients (kν0) in shock tube experiments. Collision broadening parameters (2γAr, 2γN2, and 2γH2O) were then calculated assuming the linear dependence of ΔνC with pressure—the 2γN2 and 2γH2O values were inferred from 2γAir and the equilibrium concentration of N2 and H2O of a given flame. The temperature dependences of 2γi in our temperature range are, respectively, 1.0, 0.75, and 0.87 for Ar, N2, and H2O. The collision broadening cross sections (σ) deduced from 2γi values are expressed with an assumed form, σi(T)=σi,0(T0/T)k, T0=1000 K: for Ar, σAr,0=63.3 (Å2), k=0.50; for N2, σN2,0=68.0 (Å2), k=0.25; for H2O, σH2O,0=188.8 (Å2), k=0.37. 相似文献
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150.
Anuar Kassim Saravanan Nagalingam Ho Soon Min Noraini Karrim 《Arabian Journal of Chemistry》2010,3(4):243-249
The structure and morphology of ZnS thin films were investigated. ZnS thin films have been grown on an indium tin oxide glass substrate by electrodeposition method using zinc chloride and sodium thiosulfate solutions at room temperature. The X-ray diffraction patterns confirm the presence of ZnS thin films. From the AFM images, grain size decreases as the cathodic potential becomes more negative (from ?1.1 to ?1.3 V) at various deposition periods. Comparison between all the samples reveals that the intensity of the peaks increased, indicating better crystalline phase for the films deposited at ?1.1 V. These films show homogeneous and uniform distribution according to AFM images. On the other hand, XRD analysis shows that the number of ZnS peaks increased as deposition time was increased from 15 to 30 min at ?1.1 V. The AFM images show thicker films to be formed at ?1.1 V indicating more favourable condition for the formation of ZnS thin films. 相似文献