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991.
Tongmou Geng Guofeng Chen Can Zhang Lanzhen Ma Weiyong Zhang Hongyu Xia 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(11):1004-1011
AbstractA mesoporous covalent triazine framework, PCPDI, was synthesized via an aromatic nitrile trimerization reaction of N,N′-di(4-cyanphenyl)- 3,4,9,10-tetracarboxydiimide (CPDI) by CF3SO3H catalyzed at 40?°C and this method avoids the use of noble metal catalyzers or high temperature reaction. PCPDI exhibits high thermal stability and strong fluorescence. The PCPDI shows ultrahigh sensitivity to tracing o-nitrophenol in chloroform with KSV constant of 1.74?×?105 L mol?1 and detection limit (LOD) of 1.72?×?10?11?mol L?1. 相似文献
992.
In this article, the poly(methyl methacrylate)/montmorillonite (PMMA/MMT) organic-inorganic hybrid materials were prepared by conventional free radical polymerization and reversible addition-fragmentation chain transfer (RAFT) polymerization, respectively. The kinetics comparison of these two polymerizations was studied. The PMMA/MMT hybrid materials were characterized by gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). According to these results, we knew that the polymerization behavior of MMA showed controlled/living radical polymerization (CLRP) characteristics under the control of RAFT agent. The incorporation of RAFT agent and MMT nanoparticles improved the thermal properties of polymers, and the thermal stability of polymers increased with increasing content of MMT nanoparticles. The structures and morphologies of PMMA/MMT hybrid materials were characterized by FT-IR, XRD and TEM. These results showed that the MMA monomer can be initiated and propagated in the clay layers of MMT via the control of RAFT agent, and then the exfoliated structure was obtained for the hybrid materials. 相似文献
993.
Arthur E. Martell Ramunas J. Motekaitis Eric T. Clarke Rita Delgado Yizhen Sun Rong Ma 《Supramolecular chemistry》2013,25(3-4):353-363
Abstract In our studies of the stability constants of metal complexes, we have investigated a number of macrocyclic ligands with pendant donor groups. The ligands are characterized by the fact that they have nitrogen donors in the macrocyclic ring and oxygen or sulfur donors in the pendant arms. These ligands represent seven different macrocycles, and by varying the pendant donor groups, ten different ligands are indicated. The affinities of these ligands for fifteen metal ions will be described. The Fe(III) complex of triazanonane with o-hydroxypyridyl or o-hydroxybenzyl pendant donor groups are the most stable ferric complexes ever reported. The In(III) complex of triazacyclononane with pendant mercaptoethyl donor groups, is exceptionally stable. Also, the Ca(II) complex of DOTA probably has the highest stability of any calcium(II) complex. These, and other comparisons will be made on the basis of the thermodynamic stability constant data for the ligands described. 相似文献
994.
A new fluorescent probe with a long-wavelength emission and multiple hydrogen bond sites for guanine, 3-(4-chloro-6-p-nitrophenoxy-1,3,5-triazinylamino)-7-dimethylamino-2-methylphenazine (CNTDP), was designed and synthesized by using cyanuric chloride as a molecular scaffold, neutral red as a fluorophore and p-nitrophenol as an assistant unit. The recognition behavior of CNTDP for guanine and its spectroscopic properties in different solvents were investigated. It was found that the probe's fluorescence can be selectively quenched by guanine instead of thymine, indicating that fully complementary hydrogen bonding plays a key role in such a recognition process. In addition, the fluorescence quenching mechanism of the probe by guanine and the electronic effects of neutral red, triazine ring and p-nitrophenol moieties on the fluorescence of the whole molecule were also discussed. 相似文献
995.
Z. Y. Zhang B. Wu Y. H. Tang Z. X. Li Z. L. Sun L. Y. Chen Y. B. Ji C. H. Ma C. G. Huang 《Journal of Analytical Chemistry》2013,68(8):716-721
To characterize of the constituents in rat urine after oral administration of Radix Astragali decoction, a HPLC-DAD-MS/MS technique had been developed. Urine collected from 0 to 24 h, after administration, was purified using a C18 solid-phase extraction cartridge, and then detected by an on-line MS/MS detector. By comparing the retention times and MS/MS data with those obtained from authentic compounds and the published data, a total of 11 compounds including six flavonoids, one dipeptide, one triterpenoid and three of their metabolites in urine were identified. Compounds daidzein, genistein, quercetin, L-asparamide-D-phenylalanine, 4,2′,4′-trihydroxychalcone, Astragaloside-IV, daidzein sulfate, and kaempferol sulfate were for the first time detected by HPLC-MS/MS technique in urine. The present research results success-fully narrowed the range of effective constituents to be found in Astragalus membranaceus and would be useful for the following action mechanism research of this traditional Chinese medicine in treating various diseases. 相似文献
996.
L. N. Sobenina Z. V. Stepanova O. V. Petrova J. Sh. Ma G. Yang A. A. Tatarinova A. I. Mikhaleva B. A. Trofimov 《Russian Chemical Bulletin》2013,62(1):88-92
Cross-coupling of 2-(biphenyl-4-yl)pyrroles derived from 1-(biphenyl-4-yl)ethanone oximes and acetylene with 3-bromo-1-phenylprop-2-yn-1-one on aluminum oxide gave 3-[5-(biphe-nyl-4-yl)pyrrol-2-yl]-1-phenylprop-2-yn-1-ones in 35–46% yields. 相似文献
997.
One new cadmium coordination polymer, [Cd(2,4-Dcp)2(4,4-Bipy)] n (I) (2,4-HDcp = 2,4-dichlorophenoxyacetic acid, 4,4′-Bipy = 4,4′-bipyridine) with 2D layer structure, has been prepared by the hydrothermal synthesis and characterized by elemental analysis, IR, TGA and single-crystal X-ray diffraction. Complex I crystallizes belong to monoclinic system and has C2/c space group. Each Cd2+ ion is six-coordinated and located at an octahedral geometry. The Cd2+ ions are linked by bidentate 2,4-Dcp groups into a linear chain in which the benzene rings of 2,4-Dcp ligands point alternately up and down. These chains are further connected into a sandwich-like layer though 4,4′-Bipy ligands. Furthermore, the photoluminescence and life-time of I in the solid state have been studied. 相似文献
998.
Phosphate esters are important commercial products that have been used both as flame retardants and as plasticizers. To analyze these compounds by gas chromatographic mass spectrometry, it is important to understand the mass spectra of these compounds using various ionization modes. This paper is a systematic overview of the electron impact (EI), electron capture negative ionization (ECNI) and positive chemical ionization (PCI) mass spectra of 13 organophosphate esters. These data are useful for developing and optimizing analytical measurements. The EI spectra of these 13 compounds are dominated by ions such as H4PO4+, (M ? Cl)+, (M ? CH2Cl)+ or (M)+ depending on specific chemical structures. The ECNI spectra are generally dominated by (M ? R)?. The PCI spectra are mainly dominated by the protonated molecular ion (M + H)+. The branching of the alkyl substituents, the halogenation of the substituents and, for aromatic phosphate esters, ortho alkylation of the ring are all significant factors controlling the details of the fragmentation processes. EI provides the best sensitivity for the quantitative measurement of these compounds, but PCI and ECNI both have considerable qualitative selectivity. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
999.
Mingliang Xin Yujie Ma Kai Xu Mingcai Chen 《Journal of Thermal Analysis and Calorimetry》2013,114(3):1167-1175
A study on the efficiency of bio-based compound as stabilizer for linear low density polyethylene (LLDPE) is reported. A water extract from Ampelopsis grossedentata (Dihydromyricetin) is used. Its stabilizing activity is compared with two commercial phenolic antioxidants: methyl gallate (MG) and Irganox 1010. Based on the measurement of the oxidation onset temperature (OOT) of LLDPE/antioxidant samples, it is found that the antioxidant ability of the three kinds of antioxidants is in the following order: DMY > 1010 > MG. The antioxidant ability and thermal decomposition activation energy (E a) of antioxidants are further examined by thermal gravimetric analysis. The effects of water extraction on the migration resistance of LLDPE/antioxidants are also evaluated by monitoring the OOT change, demonstrating that DMY retained high stability against migration. 相似文献
1000.
Przemysław Rybiński Grażyna Janowska Małgorzata Jóźwiak Marek Jóźwiak 《Journal of Thermal Analysis and Calorimetry》2013,113(1):43-52
The article presents the effect of attapulgite (ATT) and its synergic action with carbon or silica on the thermal properties and flammability of cross-linked styrene–butadiene rubber. It has been shown that ATT is active filler improving the thermal and mechanical properties of composites containing this aluminosilicate. The decreased flammability of vulcanizates containing ATT compared to that of unfilled vulcanizates results from good insulating properties of the ATT used. The considerable reduction in the flammability of composites containing ATT and carbon nanofiber or silica is connected, first of all, with the formation of a homogeneous boundary layer. 相似文献