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151.
High molecular weight copoly(ether ketone)s (PEK) based on 4-(4-hydroxyphenyl)-1-phthalazinone (DHPZ)/4,4′-thiobisphenol (TBP)/4,4′-diflourodiphenylketone (DFK) were prepared by nucleophilic substitution polycondensation. The copolymers were characterized by FT- and ^1H-NMR. Thermal properties and solubility of copolymers were studied. 相似文献
152.
The molecular intrinsic characteristic contour (MICC) is defined as the set of all the classical turning points of electron movement in a molecule. Studies on the MICCs of some medium organic molecules, such as dimethylether, acetone, and some homologues of alkanes, alkenes, and alkynes, as well as the electron density distributions on the MICCs, are shown for the first time. Results show that the MICC is an intrinsic approach to shape and size of a molecule. Unlike the van der Waals hard-sphere model, the MICC is a smooth contour, and it has a clear physical meaning. Detailed investigations on the cross-sections of MICCs have provided a kind of important information about atomic size changing in the process of forming molecules. Studies on electron density distribution on the MICC not only provide a new insight into molecular shape, but also show that the electron density distribution on the boundary surface relates closely with molecular properties and reactivities. For the homologues of alkanes, Rout(H), Dmin, and Dmax (the minimum and maximum of electron density on the MICC), all have very good linear relationships with minus of the molecular ionization potential. This work may serve as a basis for exploring a new reactivity indicator of chemical reactions and for studying molecular shape properties of large organic and biological molecules. 相似文献
153.
A simple, accurate method based on capillary electrophoresis with electrochemical detection (CE–ED) has been developed to determine loureirin A, loureirin B and dracorhodin for differentiation of Resina Draconis from Sanguis Draconis. The effects of some important factors such as acidity and concentration of running buffer, separation voltage, injection time, and applied potential on the CE–ED working electrode were investigated. Under the optimum conditions, the three analytes could be well separated within 30 min in a 75 cm capillary at a separation voltage of 14 kV in a 80 mmol L?1 borate buffer (pH 9.24). The working electrode was a 300-μm-diameter carbon disc electrode positioned opposite the outlet of the capillary in a wall-jet configuration and was set at a potential of 0.90 V (vs. SCE). Excellent linearity was established over two orders of magnitude with detection limits (S/N = 3) ranging from 3 × 10?7 g mL?1 to 1 × 10?6 g mL?1 for all three analytes. The relative standard deviations of peak current and migration times of loureirin A, loureirin B and dracorhodin were 2.1, 1.7, 4.4 and 2.9, 2.8, 3.3% (n = 5), respectively. The recoveries of three constituents ranged from 98.8 to 101.8%. The methodology has been successfully applied to analyze and differentiate the actual samples with satisfactory assay results. 相似文献
154.
Yun Gong Changwen Hu Hui Li Wanlong Pan Xueli Niu Zhifa Pu 《Journal of Molecular Structure》2005,740(1-3):153-158
Two nickel (imidazole) complexes, Ni(im)6Cl2·4H2O (1) and Ni(im)6(NO3)2 (2) (im=imidazole) have been synthesized and characterized by elemental analysis, IR, UV, TG and single crystal X-ray diffraction. 1 crystallizes in the triclinic space group P-1 with a=8.800(6) Å, b=9.081(6) Å, c=10.565(7) Å, =75.058(9)°, β=83.143(8)°, γ=61.722(8)°, V=718.3(8) Å3, Z=1 and R1 (wR2)=0.0469 (0.1497). 2 crystallizes in the trigonal space group R-3 with a=12.370(6) Å, b=12.370(6) Å, c=14.782(14) Å, =90.00°, β=90.00°, γ=120.00°, V=1959(2) Å3, Z=3 and R1 (wR2)=0.0358 (0.0955). 1 and 2 exhibit different supramolecular network due to their different counter anions and different hydrogen bonding connection. In compound 1, [Ni(im)6]2+ cation and counter anions Cl− alternatively array in an ABAB fashion via N–HCl hydrogen bonding. In compound 2, the plane of each NO32− is almost parallel and each NO32− connect three different [Ni(im)6]2+ cations via N–HO hydrogen bonding. 相似文献
155.
A series of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)-based organic-inorganic hybrid materials for anion exchange were prepared through sol-gel process of polymer precursors PPO-Si(OCH3)3. PPO-Si(OCH3)3 were obtained from the reaction of bromomethylated PPO with 3-aminopropyl-trimethoxysilane (A1110). These polymer precursors then underwent hydrolysis and condensation with additional A1110 to generate hybrid materials. The reaction to produce polymer precursors was identified by FTIR; while FTIR, TGA, XRD, SEM, as well as conventional ion exchange capacity (IEC) measurements were conducted for the structures and properties of the prepared hybrids. TGA results show that this series of hybrid materials possess high thermal stability; XRD and SEM indicate that the prepared hybrid materials are amorphous and the inorganic and organic contents show good compatibility if the ratio between them is proper. The IEC values of the hybrid materials due to the amine groups range from 1.13 mmol/gBPPO (material i) to 4.80 mmol/gBPPO (material iv). 相似文献
156.
Electrostatic layer-by-layer assembled carbon nanotube multilayer film and its electrocatalytic activity for O2 reduction 总被引:1,自引:0,他引:1
Zhang M Yan Y Gong K Mao L Guo Z Chen Y 《Langmuir : the ACS journal of surfaces and colloids》2004,20(20):8781-8785
Multilayer films of shortened multiwalled carbon nanotubes (MWNTs) are homogeneously and stably assembled on glassy carbon electrodes with the layer-by-layer (LBL) method, based on electrostatic interaction of positively charged poly(diallyldimethylammonium chloride) and negatively charged and shortened MWNTs. The film assembly and electrochemical property as well as the electrocatalytic activity toward O2 reduction of the MWNT multilayer film are studied. Scanning electron microscopy, the quartz crystal microbalance technique, ultraviolet-visible-near-infrared spectroscopy, and cyclic voltammetry are used for characterization of film assembly. Experimental results revealed that film growth is uniform, almost with the same coverage of the MWNTs in each layer, and that the assembled MWNTs are mainly in the form of small bundles or single tubes on the electrodes. Electrochemical studies indicate that the LBL assembled MWNT films possess a remarkable electrocatalytic activity toward O2 reduction in alkaline media. This property, combined with the well-dispersed, porous and conductive features of the MWNT film illustrated with the LBL method, suggests the potential application of the MWNT film for constructing an efficient alkaline air electrode for energy conversions. 相似文献
157.
Chung‐Cheng Chang Kuo‐Ching Yang Jeng‐Gong Guo Leigh‐May Huang Li‐Chyung Wang Gene‐Hsiang Lee Shie‐Ming Peng 《中国化学会会志》2003,50(5):965-971
The insertion reaction of CS2 with Mg(NR2)2 (R= Et, iPr), MgR′2 (R′= Et, Ph) and R″MgBr (R″= iPr, Ph) respectively lead solid products, Mg(S2CNR2)2(THF)n ( 1 : R= Et, n=2; 2 : R= iPr, n=1), Mg(S2C′R)2(THF)2 ( 3 : ′R= Et, 4 : ′R= Ph), BrMg(S2C″R) (THF)3 ( 5 : ″R= iPr, 6 : ″R= Ph) in which the inserted carbon disulfides act as terminal chelating ligands. These compounds were characterized with 1H, 13C NMR, IR spectroscopy, mass spectrometry, elemental analyses, and X‐ray crystallography. 相似文献
158.
Gong H Garcia-Turiel J Vasilev K Vinogradova OI 《Langmuir : the ACS journal of surfaces and colloids》2005,21(16):7545-7550
The growth, morphology, and interaction/adhesion properties of supported poly(sodium 4-styrenesulfonate)/poly(allylamine hydrochloride) (PSS/PAH) and DNA/PAH multilayers were investigated by means of surface plasmon resonance spectroscopy, atomic force microscope (AFM) imaging, and AFM-related force measurements. Multilayers were assembled on a prelayer of poly(ethylenimine) (PEI) both with and without drying. SPR results showed a linear growth of the assembly in the case of PSS/PAH multilayers and nonlinear growth for DNA/PAH multilayers. Measurements of forces acting between a bare glass sphere and a multilayer-coated surface indicated repulsive or attractive forces, depending on surface charge, which suggests that, on approach, electrostatic forces dominate. On separation, we observed large pull-off forces in the case of positively charged multilayers and weak pull-off forces in the case negatively charged multilayers. Multiple adhesions and plateau regions observed on separation were interpreted in terms of a bridging of multiple polymer chains between the glass particle and the multilayer and a stretching of the polyelectrolyte loops. The dependence of the pull-off force on the number of deposited layers shows regular oscillations. 相似文献
159.
The effects of the hyperbranched polyester with hydroxyl end groups (HBPE‐OH) on the curing behavior and toughening performance of a commercial epoxy resin (diglycidyl ether of bisphenol A, DGEBA) were presented. The addition of HBPE‐OH into DGEBA strongly increased its curing rate and conversion of epoxide group due to the catalytic effect of hydroxyl groups in HBPE‐OH and the low viscosity of the blend at curing temperature. The improvements on impact strength and critical stress intensity factor (or fracture toughness, K1c) were observed with adding HBPE‐OH. The impact strength was 8.04 kJ m?1 when HBPE‐OH reached 15 wt% and the K1c value was approximately two times the value of pure epoxy resin when HBPE‐OH content was 20 wt%. The morphology of the blends was also investigated, which indicated that HBPE‐OH particles, as a second phase in the epoxy matrix, combined with each other as the concentration of HBPE‐OH increased. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
160.
Jingyu Wang Jing Zheng Yanbin Cai Jinxin Zheng Jie Gao Qingqiu Gong Zhimou Yang 《中国科学:化学(英文版)》2016,59(6):719-723
In this study, we used the 4-nitro-2,1,3-benzoxadiazole (NBD) as an aromatic capping group for a peptide to construct the supramolecular nanofibers. Taking the advantage of the fluorescence property of NBD, we could directly observe the cellular distribution of the self-assembled nanofibers. We found that the distributions of the nanofibers of NBD-FFETIGGY are different in four mammalian cells and two plant cells. The nanofibers are mainly located at the surface of two mammalian cells and one plant cell, while in the intracellular space of other cells. Different distributions of nanofibers lead to different protein binding patterns of the nanofibers in two different cell lines. We believe that a useful and versatile platform has been offered to the image cellular distribution of nanofibers, which can provide useful information to the biological functions of the self-assembled nanostructures. 相似文献