苯乙烯-丁二烯-苯乙烯/聚乙烯基甲基醚共混体系相容性的FT-IR及DSC研究

嵌段高聚物、均聚物共混体系相容性是近年来研究的热点。本工作以光学显微镜、DSC、FT-IR为手段,研究了三嵌段高聚物苯乙烯-丁二烯-苯乙烯(SBS);SBS-48、SBS-30,SBS-28与聚乙烯基甲基醚共混体系的相容性。DSC结果表明,随SBS中PS含量的升高,体系相容性变好,PS段分子量增大,也有助于体系相容。FT-IR结果表明PVME中COCH_3在1100cm~(-1)附近呈现的双峰的相对强度对体系的相容性十分敏感,而由于苯环C—H振动产生的698cm~(-1)峰位却不象PS/PVME体系那样随相容性的改变而有显著的改变。总而言之,嵌段高聚物SBS/均聚物PVME共混体系中,体系的相容性依赖于嵌段高聚物在体系中的组份含量及嵌段高聚物中PS的重量百分含量,PS段分子量的大小对体系相容性也有影响。     

A new veratramine alkaloid from the bulbs of Fritillaria hupehensis

A new highly conjugated alkaloid of veratramine type, 225,25S,5α-veratramine-7(8),12(14)-diene-3β,13β,23β-triol-6-one (1), was isolated from the bulbs of Fritillaria hupehensis Hsiao et K.C. Hsia. Its structure was determined on the basis of spectroscopic evidences.     

THE EFFECT OF MODIFICATION OF COORDINATING GROUPS ON THE CATALYTIC BEHAVIORS OF POLYMER CATALYSTS

Several polymer-supported palladium complex catalysts containing two different coordinatinggroups were prepared and the cooperative effect of the coordinating groups on the catalytic behaviorsof polymer catalysts was studied. It was found that poly(acrylic acid-co-acrylonitrile)-Pd complex(PAA-AN-Pd) is a more active and stable catalyst for hydrogenation than both poly(acrylic acid)-Pd and poly(acrylonitrile)-Pd complexes. A marked change of catalytic behaviors of poly(N-substituted maleamic acid-co-styrene)-Pd complexes was observed in comparison with poly(maleicacid-co-styrene)-Pd complex. Acetophenone was reduced to 1-phenyl ethanol by poly(N-phenylmaleamic acid-Co-styrene)-Pd complex (N-1-Pd), but ethylbenzene was obtained using poly(maleicacid-co-styrene)-Pd complex as a catalyst. The influence of solvents, additives and N/Pd gramatomic ratio on the catalytic behaviors of the polymer complexes was investigated.     

Reduced viscosity polymer matrices for microchip electrophoresis of double-stranded DNA

On a polymethylmethacrylate (PMMA) microchip, double-stranded DNA fragments with a wide size range from 50 bp to 20 kbp were separated by two polymer solutions. One was a hydroxypropylmethylcellulose-4000 (HPMC-4000) solution of 1.3% (w/v) to separate fragments below 590 bp, and another was a mixed four molecular weight poly(ethylene oxide) solution at a total concentration of 0.1% to separate fragments above 520 bp. The widths at half height (wh) of the fragments had a good relationship with their migration times (tR) in both polymer solutions. Such a relationship was suitable for obtaining the wh values of unresolved peaks, calculating the resolution of two adjacent fragments, and optimizing microchip separation matrices. Based on the relativity, a low viscosity medium containing 2% HPMC-50 and 8% glucose was optimized for high-performance separation of a phiX174 HaeIII restriction fragment digest.     

A novel zirconocene/ultradispersed diamond black powder supported catalytic system for ethylene polymerization

A novel carrier of ultradispersed diamond black powder (UDDBP) was used to support metallocene catalyst. Al₂O₃ was also used as carrier in order to compare with UDDBP. Supported catalysts for ethylene polymerization were synthesized by two different reaction methods. One way was direct immobilization of the metallocene on the support, the other was adsorption of MAO onto the support followed by addition of the metallocene. Four supported catalysts Cp₂ZrCl₂/UDDBP, Cp₂ZrCl₂/Al₂O₃, Cp₂ZrCl₂/MAO/UDDBP and Cp₂ZrCl₂/Al₂O₃/MAO were obtained. The content of the zirconium in the supported catalyst was determined by UV spectroscopy. The activity of the ethylene polymerization catalyzed by supported catalyst was investigated. The influence of Al/Zr molar ratio and polymerization temperature on the activity was discussed. The polymerization rate was also observed.     

Baeyer-Villiger单加氧酶在有机合成中的应用

综述了Baeyer-Villiger单加氧酶在有机合成中的应用.较之传统的化学反应, 氧化酶催化剂反应有较好的选择性、可控性和经济性. 环己酮加氧酶是一种还原型辅酶I (NADPH)依赖型氧化酶, 是最早被报道能够催化Baeyer-Villiger氧化的酶. 这些重要反应产生了合成化学家很感兴趣的扩环产物. 环己酮加氧酶也是有用的生物催化剂, 由于辅酶再生的问题已被工程菌克服了, 所以能像全细胞催化剂那样使用. 对酮包括杂环酮进行Baeyer-Villiger氧化和动态动力学拆分, 放大这种反应作为合成路线是很有前途的.     

Patterned polyelectrolyte multilayer: surface modification for enhancing selective adsorption

This paper describes the use of surface chemical modification to enhance the difference of the surface charge on a patterned polyelectrolyte multilayer, which can be used for selectively adsorbing functional materials. We fabricated a patterned multilayer by combining the layer-by-layer self-assembly technique and photolithography and taking advantage of the different solubility of polyelectrolyte multilayers of diazo resins (DAR)/poly(acrylic acid) before and after UV irradiation. This patterned surface can be used as a matrix for selective adsorption of small molecular dyes, such as Methylene Blue. However the difference in surface charge on the patterned surface was not enough when we used it to selectively adsorb polystyrene (PS) nanoparticles using electrostatic force as the driving force. Therefore, we modified the patterned surface by interfacial chemistry. After modification, the patterned polyelectrolyte multilayer can be used as a good matrix for selective adsorption of PS nanoparticles with both positive and negative charges.     

Poly[(μ2‐1,3‐di‐4‐pyridylpropane‐κ2N:N′)(μ3‐glutarato‐κ3O:O′:O′′)dizinc(II)]

The title compound, [Zn₂(C₅H₆O₄)₂(C₁₃H₁₄N₂)]_n or [Zn₂(glu)₂(bpp)]_n, is a novel zinc polymer based on mixed flexible glutarate (glu) and 1,3‐di‐4‐pyridylpropane (bpp) ligands. The Zn^II center has a distorted tetra­hedral geometry and the central atom of the bpp ligand is located at a special site with a C₂ axis passing through it. A layer is formed by Zn–glu bonding. Such layers are pillared by bpp ligands, forming a three‐dimensional framework with large channels. The inverted inter­penetration of two three‐dimensional frameworks completes the mol­ecular structure.     

Study of a fluorescence quenching mechanism of enoxacin and its determination in human serum and urine samples

The maximum emission wavelength of dopamine is 317 nm with excitation at 290 nm. The relative fluorescence intensity of dopamine decreased in the presence of enoxacin, which showed that fluorescence quenching occurred. The Stern-Volmer (S-V) plot showed a nonlinear relationship between the relative fluorescence intensity of dopamine and the concentration of enoxain. The quenching mechanism was studied and the results suggested that both dynamic and static quenching processes were responsible for the observed positive deviation in the S-V plot. When the S-V plot was modified by logarithm, the linear relationship was obtained between logF ₀/F and C in the range of 0.10 to 13.0 μg/mL (where F ₀ is the relative fluorescence intensity of dopamine, F is the relative fluorescence intensity of dopamine in the presence of enoxacin, and C is the concentration of enoxacin). The fluorescence quenching method for the determination of enoxacin was developed. The linear regression equation of the calibration graph of enoxacin was C = 13.70 (logF ₀/F) − 0.5836, with the correlation coefficient 0.9984. The detection limit was 2.0 ng/mL and the relative standard deviation was 2.52%. The effects of pH, the stability of dopamine in the presence of enoxacin, and foreign ions on the determination of enoxacin have been examined. The recovery of enoxacin was from 94.9 to 103.0% in a human serum sample and from 94.9 to 108.0% in a urine sample. The method is simple, rapid, and can be used for the determination of enoxacin in human serum and urine samples with satisfactory results. The text was submitted by the authors in English.     

柱后衍生-荧光检测高效液相色谱法快速测定鲜牛奶中链霉素残留量

牛奶样品经磷酸溶液提取，提取液用苯磺酸阳离子交换柱和C18固相萃取柱净化，链霉素残留液用甲醇从C18固相萃取柱上洗脱，经旋转蒸发器减压蒸干，残渣用0．01mol／L庚烷磺酸钠溶液溶解，用柱后衍生-高效液相色谱荧光检测器在激发波长263nm和发射波长435nm测定．方法线性范围为0.01～0．10mg／kg；在0．01～0．10mg／kg范围，三个添加水平的回收率为78．3％～80．2％，变异系数(CV)为7．4％～12．4％，方法检出限为0．005mg／kg．