Regio‐ and stereospecific synthesis of polysubstituted alkenes by carbozincation of acetylenic sulfones

Tri‐ or tetrasubstituted alkenes with various substituents can be constructed regio‐ and stereospecifically by treatment of acetylenic sulfones with organozinc reagents in tetrahydrofuran followed by hydrolysis or coupling with halohydrocarbon. Copyright © 2009 John Wiley & Sons, Ltd.     

含空洞非线性材料的本构势和空洞扩展率

本文基于体胞模型的解析分析,分析了含空洞非线性材料的宏观本构势,得到了各种幂硬化指数下宏观应力和基体平均流变应力之间的相关曲线.当基体是遵循经典塑性全量理论时,这些曲线方程就是一簇依赖于空洞体积比和硬化指数的屈服面方程.当基体是粘性体时,这些方程就是粘性约束方程.通过曲线拟合的方法,本文发展了修正的Gurson方程,使之适合于不同硬化指数的情况.最后本文计算了粘性体中空洞的相对扩展率,结果与已有体胞模型的数值模拟计算结果相当一致.     

Functionalization of graphene oxide with different diisocyanates and their use as a reinforcement in waterborne polyurethane composites

Abstract

To examine the reinforcing effects of isocyanated graphene oxide (NCO-GO) on a waterborne polyurethane matrix, the surface of GO was respectively modified by isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI) and toluene diisocyanates (TDI) and then confirmed by FT-IR, Raman, TGA, XRD, TEM, AFM and SEM-EDS. The dispersity behavior between different NCO-GO and polymer was evaluated by FESEM and XRD. The nanocomposites’ chemical structure, emulsion morphology, hydrophobicity, thermal and mechanical properties were investigated by FT-IR, TEM, TGA, tensile testing machine and water contact angle test, respectively. It was shown that these properties of nanocomposites including tensile strength, initial thermal degradation and hydrophobicity were increased by the incorporation of NCO-GO, in which, particularly, the tensile stress and initial degradation temperature were respectively increased from 13.32 to 18.80?Mpa and 249 to 288?°C after the addition of TDI-GO. These superior reinforcing effects were attributed to the two-dimensional structure of NCO-GO as well as the good interfacial adhesion between the NCO-GO and WPU matrix.     

Widely wavelength switchable V-coupled-cavity semiconductor laser with ∼40 dB side-mode suppression ratio

We report the first experimental demonstration of a single-electrode-controlled digitally wavelength switchable V-coupled-cavity laser with high side-mode-suppression-ratio (SMSR) in the 40?dB range. Sixteen-channel and twenty-six channel wavelength switchable lasers with 100?GHz spacing are demonstrated with the maximal SMSR of 40?dB and 37?dB, respectively. They do not require complex gratings, multiple epitaxial growths, or complex tuning algorithms. The device size is only 500?μm×300?μm. Such a simple, compact, and high-performance laser has great potential as a low-cost alternative to existing complex tunable lasers for wide deployment in optical networks and beyond.     

Large third-order optical nonlinear effects of gold nanoparticles with unusual fluorescence enhancement

The third-order nonlinear optical properties of two solutions of gold nanoparticles protected by carbazolyldiacetylene derivatives were investigated using the Z-scan technique. Both gold nanoparticle colloid solutions in toluene show unusual fluorescent enhancement and large third-order nonlinear optical properties including nonlinear absorption and refractive effects. When extending the pi-conjugated length of the ligands, the third-order nonlinear properties of composite materials based on gold nanoparticles were enhanced accordingly.     

Morphology transition and aggregation-induced emission of an intramolecular charge-transfer compound

An intramolecular charge-transfer (ICT) compound, (TCBD)2OPV3, has been synthesized and fabricated into one-dimensional nanotubes by a reprecipitation method. The observation of SEM and TEM showed the nanotubes were formed from their zero-dimensional precursors of hollow nanospheres. Reconstruction was found to happen during the morphology transition progress. The morphology transition and reconstruction are proposed to be a "curvature strain releasing" process driven by donor-acceptor dipole-dipole interactions. An aggregation-induced emission (AIE) effect was observed for (TCBD)2OPV3. Both aggregates of vesicles and nanotubes were observed to be good red emitters with near-infrared end emission of 750-850 nm, which endows the material with potential applications in the fields of optical devices, biosensors, and biolabels.     

SmCl3-catalyzed C-acylation of 1,3-dicarbonyl compounds and malononitrile

A recyclable, convenient, and efficient catalytic system for C-acylation of 1,3-dicarbonyl compounds and malononitrile with acid chlorides has been developed, giving moderate to excellent yields under mild conditions. This is the first catalytic example of such reactions. In addition, by applying this protocol as the key step, 3,5-disubstituted-1H-pyrazole-4-carboxylate can easily be synthesized in high yields in a one-pot procedure.     

Liquid oxygen compatibility and thermal stability of bisphenol A and bisphenol F epoxy resins modified by DOPO

Bisphenol A and bisphenol F epoxy resins (BA and BF) were chemically modified by 9,10‐Dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide to improve their liquid oxygen compatibility. The structures of the modified epoxy resins were confirmed by Fourier transform infrared spectroscopy. Significant enhancement of liquid oxygen compatibility for the modified resins was detected according to the liquid oxygen mechanical impact test. Thermogravimetric analysis showed that during the degradation in oxygen atmosphere, the modified resins exhibited much lower weight loss rate and possessed much higher char residues than the control ones. Based on limited oxygen index test, better flame retardancy was also observed for the modified resins. In addition, the modified BA system was more excellent than the modified BF system in liquid oxygen compatibility, thermal stability, and flame retardancy. X‐ray photoelectron spectroscopy analysis showed that after the liquid oxygen impact, the modified resins was still in oxidation stage and the control ones already begun to decompose and char. It could be attributed to formation of the phosphoric oxyacid on the surface of the modified resins, which prevented decomposition and inhibited the reaction between the specimen and liquid oxygen. Copyright © 2014 John Wiley & Sons, Ltd.