Exfoliation through an ionic exchange reaction of layered silicate clays, including synthetic fluorinated mica (Mica) and natural montmorillonite (MMT), were achieved by using polyvalent amine salts as the intercalating agents. The requisite polyamine was synthesized from the epoxy/amine coupling reaction, involving a trifunctional poly(oxypropylene)-triamine (ca. 440 g/mol Mw) and diglycidyl ether of bisphenol-A. The polyamine was a mixture of oligomeric adducts consisting of multiple amine functionalities and a branched backbone. Partial acidification by HCl addition generated a series of amine salts that affected the intercalation and the expansion of the silicate interlayer in the range of 15.2-60.0 Å XRD d spacing. At the specific acidified ratio (H+/amine = 1/3 equiv ratio), the polyamine salts rendered the clay’s layered structure into randomization. The result was confirmed by using XRD and transmission electronic microscopy (TEM). The hybrids of polyamines and Mica or MMT were blended into epoxy resins and cured into nanocomposites, which exhibited the improvements of thermal stability and hardness. 相似文献
The unique polymeric silsesquioxane/4,4′-diglycidyether bisphenol A (DGEBA) epoxy nanocomposites have been prepared by sol-gel method. The structure of nanocomposites was characterized by attenuated total reflectance (ATR) and solid state 29Si NMR. The characteristic intensity of trisubstituted (T) structure was higher than that of tetrasubstituted (Q) structure from solid state 29Si NMR spectra of 3-isocyanatopropyltriethoxysilane (IPTS) modified epoxy. The activation energies of curing reaction of epoxy system and IPTS modified epoxy system are 28-66 kJ/mol and 57-75 kJ/mol, respectively, by Ozawa’s and Kissinger’s methods. The triethyoxysilane side chain of IPTS modified epoxy might interfere the curing reaction of epoxy/amine and increase the activation energy of curing. The thermal degradation of nanocomposites was investigated by Thermogravimetric analysis (TGA). The char yield of nanocomposites was proportional to the 2-(diphenylphosphino)ethyltriethoxysilane (DPPETES) moiety content at high temperature. A higher char content could inhibit thermal decomposition dramatically and enhance the thermal stability. Moreover, the nanocomposites possess high optical transparency. 相似文献
ZnO/polystyrene composite particles were synthesized by Pickering emulsion polymerization. ZnO nanoparticles were first prepared by reaction of zinc acetate and sodium hydroxide in ethanol medium. Then different amount of styrene monomer was emulsified in water in the presence of ZnO nanoparticles either by mechanical stirring or by sonication, followed by polymerization of styrene. Two kinds of initiators were used to start the polymerization, azobisisobutyronitrile (AIBN) and potassium persulfate (KPS). The X-ray diffraction pattern verified the crystal structure of ZnO and FT-IR spectra evidenced the existence of ZnO and polystyrene (PS) in ZnO/polystyrene composite particles. Different morphologies were observed for the composite particles when using different initiators. From TEM photographs, AIBN-initiated system produced mainly core-shell composite particles with PS as core and ZnO as shell, while KPS-initiated system showed both composite particles and pure PS particles. Two schemes of reaction mechanism were proposed to explain the morphologies accordingly. Both systems of composite particles showed good pH adjusting ability. 相似文献
Treatment of 3,5-bis(trifluoromethyl)-2-(2'-pyridyl)pyrrole (fpyroH) with Pt(DMSO)2Cl2 and Na2CO3 in THF solution gave a light-yellow complex denoted as [Pt(fpyro)2] (1). A single-crystal X-ray diffraction study on 1 revealed a large conformational distortion around the platinum(II) center, which is attributed to interligand repulsion between the pyridyl groups and the CF3 substituents of the nearby pyrrolides. Reaction of 1 with N- and C-donor ligands such as acetonitrile, pyridine, isocyanide, and CO affords the adducts [Pt(fpyro)2(L)], L = NCMe (2), pyridine (3), CNBut (4), and CO (5), showing formation of one monodentate fpyro ligand by release of the strain energy. The variable-temperature 1H NMR studies showed a static structure for the N-substituted adducts 2 and 3, whereas the C-adducts 4 and 5 are shown to be more labile, displaying a pairwise exchange of bidentate and monodentate fpyro ligands in solution. Addition of ethanol to the coordinated CO in 5 during recrystallization is also established, affording an ethoxycarbonyl complex [Pt(fpyro)(fpyroH)(CO2Et)] (6), which was isolated as a crystalline solid and can be readily converted back to 5 and free ethanol upon dissolution at room temperature. 相似文献
A capillary electrophoresis (CE) method coupled with electrochemiluminescence (ECL) detection for the analysis of glyphosate (GLY) and its major metabolite aminomethylphosphonic acid (AMPA) is presented. Complete separation of GLY and AMPA was achieved in 8 min using a background electrolyte of 20 mM sodium phosphate (pH 9.0) and a separation voltage of 21 kV. ECL detection was performed with an indium tin oxide (ITO) working electrode bias at 1.6 V (vs. a Pt-wire reference) in a 30 0mM sodium phosphate buffer (pH 8.0) containing 3.5mM Ru(bpy)3 2+ (where bpy=2.2'-bipyridyl). Linear correlation (r>or=0.997) between ECL intensity and analyte concentration was obtained in the ranges 0.169-16.9 and 5.55-111 microg ml(-1) for GLY and AMPA, respectively. The limits of detection (LODs) for GLY and AMPA in water were 0.06 microg ml(-1) and 4.04 microg ml(-1), respectively. The developed method was applied to the analysis of GLY in soybeans. The LOD of GLY in soybean was 0.6 microg g(-1). Total analysis time including sample pretreatment was less than 1h. 相似文献
This study describes a new class of indolylphosphine ligands, which can be easily accessed by a simple one-pot assembly from commercially available indoles, acid chlorides, and chlorophosphines. A combination of these three starting materials provides a high diversification of the ligand structure. The application of this ligand array in palladium-catalyzed Suzuki-Miyaura coupling reaction of aryl chlorides with arylboronic acids is described. A catalyst loading down to 0.01 mol % of Pd can be achieved. 相似文献
A diglycidylether sulfone monomer (sulfone type epoxy monomer, SEP) was prepared from bis(4-hydroxyphenyl) sulfone (SDOL) and epichlorohydrin without any NaOH or KOH as basic catalyst. FT-IR, 1H NMR, 13C NMR and mass spectroscopic instruments were utilized to determine the structure of the SEP monomer. The cured SEP epoxy material exhibited not only a higher Tg (163.81 °C) but also a higher Tg than pristine DGEBA (from 111.25 °C to 139.17 °C) when the SEP monomer moiety had been introduced into the DGEBA system. The thermal stability of cured epoxy herein was investigated by thermogravimetric analysis (TGA). The results demonstrated that the sulfone group of the cured SEP material decomposed at lower temperatures and formed thermally stable sulfate compounds, improving char yield and enhancing resistance against thermal oxidation. Additionally, the IPDT and char yield of the cured SEP epoxy (IPDT = 1455.75, char yield = 39.67%) exceeded those of conventional DGEBA epoxy (IPDT = 667.27, char yield = 16.25%). 相似文献
A series of blue phosphorescent iridium(III) complexes 1-4 with nonconjugated N-benzylpyrazole ligands were synthesized and their structural, electrochemical, and photophysical properties were investigated. Complexes 1-4 exhibit phosphorescence with yields of 5-45 % in degassed CH2Cl2. Of the compounds, 1 showed emission that was nearly true blue at 460 nm with a lack of vibronic progression. These photophysical data clearly demonstrate that the methylene spacer of the cyclometalated N-benzylpyrazole chelate effectively interrupts the pi conjugation upon reacting with a third L X chelating chromophore. This gives a feasible synthesis for the blue phosphorescent complexes with a sufficiently large energy gap. In another approach, these complexes were investigated for their suitability for the host material in phosphorescent OLEDs. The device was synthesized by using 1 as the host for the green-emitting [Ir(ppy)3] dopant, which exhibits an external quantum conversion efficiency (EQE) of up to 11.4 % photons per electron (and 36.6 cdA(-1)), with 1931 Commission Internationale de L'Eclairage (CIE) coordinates of (0.30, 0.59), a peak power efficiency of 21.7 lmW(-1), and a maximum brightness of 32000 cdm(-2) at 14.5 V. At the practical brightness of 100 cdm(-2), the efficiency remains above 11 % and 18 lmW(-1), demonstrating its great potential as the host material for phosphorescent organic light-emitting diodes. 相似文献
An efficient formal total synthesis of (+) cortistatins A and J has been accomplished, by exploiting a highly diastereoselective intramolecular [4+3] cycloaddition of epoxy enolsilanes as the key reaction to construct rings B and C of the cortistatins in one step. 相似文献
The fabrication of electrospun polymer fibers is demonstrated with anisotropic cross‐sections by applying a simple pressing method. Electrospun polystyrene or poly(methyl methacrylate) fibers are pressed by flat or patterned substrates while the samples are annealed at elevated temperatures. The shapes and morphologies of the pressed polymer fibers are controlled by the experimental conditions such as the pressing force, the pressing temperature, the pressing time, and the surface pattern of the substrate. At the same pressing force, the shape changes of the polymer fibers can be controlled by the pressing time. For shorter pressing times, the deformation process is dominated by the effect of pressing and fibers with barrel‐shaped cross‐sections can be generated. For longer pressing times, the effect of wetting becomes more important and fibers with dumbbell‐shaped cross‐sections can be obtained. Hierarchical polymer fibers with nanorods are fabricated by pressing the fibers with porous anodic aluminum oxide templates.