Alternating copolymer of thiophene andN‐(phenylethynyl)pyrrole. New π‐conjugated alternating five‐membered ring copolymer and its packing structure

An alternating copolymer, Copoly‐1 , of thiophene and N‐(phenylethynyl)pyrrole was prepared by palladium‐catalyzed polycondensation. Powder X‐ray diffraction (XRD) analysis indicated that Copoly‐1 formed a stacked packing structure with doubly‐running polymer main chains. Optical data support the molecular and packing structures of Copoly‐1 . © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2219–2224, 2005     

Differential pulse voltammetric determination of arsenic(III,V) and antimony (III,V) in glasses

Summary Analytical methods based on differential pulse voltammetry (DPV) have been described for the determination of total As, As(III), As(V), total Sb and Sb(III) as trace to minor constituents in complex glasses. For total As, the sample is decomposed with HF-H₂SO₄-KMnO₄. The As(V) is chemically reduced to As (III) by hypophosphite and a DPV scan is carried out at the dropping mercury electrode from –0.2 to –0.7 Vvs. SCE (E _p –0.41V). As(V) is determined by decomposing the sample in HF-H₂SO₄ and volatilizing the As(III) as AsF₃. The chemical reduction of As(V) and the DPV scan are then applied. If the glass can be decomposed with cold HF, the As(III) present in the glass can be determined by applying the DPV scan after cold sample-dissolution. For Sb(III), the sample is decomposed with HF-H₂SO₄, diluted, and adjusted to 1M in HCl. A DPV scan is conducted from –0.03 to –0.5 V (E _p –0.15 V). Sb(V) is not reduced in the 1M HCl supporting electrolyte. Total Sb is determined by using an aliquot of the sample solution adjusted to 6M in HCl. The DPV sweep is carried out from –0.5 to –0.1 V [E _p for Sb(V) and Sb(III) is –0.30 V]. The methods have been applied to a wide range of glass compositions and the results compared with values obtained by spectrophotometry and coulometric titration.

---

Bestimmung von Arsen(III, V) und Antimon(III, V) in Gläsern mit Hilfe der Differential-Puls-Voltammetrie

Zusammenfassung Analytische Methoden auf der Grundlage der Differential-Puls-Voltammetrie (DPV) für die Bestimmung des gesamten Arsens, As(III), As(V), des gesamten Antimons und Sb(III) als Spuren in komplexen Gläsern wurden beschrieben. Zwecks Bestimmung des Gesamt-As wird die Probe mit Flußsäure +Schwefelsäure + Permanganat aufgeschlossen. As(V) wird mit Hypophosphit reduziert und die DPV wird an einer Quecksilber-Tropfelektrode zwischen –0,2 und –0,7V gegen eine ges. Kalomelelektrode (E _p =–0,41V) durchgeführt. Zur Bestimmung von As(V) wird die Probe mit HF-H₂SO₄ unter Verflüchtigung des As(III) als AsF₃ aufgeschlossen. Dann erfolgt die Reduktion des As(V) und die DPV. Wenn sich das Glas mit kalter HF lösen läßt, wird anwesendes As(III) mittels DPV in dieser Lösung bestimmt. Zur Bestimmung des Sb(III) wird die Probe mit HF-H₂SO₄ zersetzt, verdünnt und bis zur 1-Molarität mit HCl versetzt. Dann wird mit DPV zwischen –0,03 und –0,5V gemessen (E _p =–0,15V). Sb(V) wird in 1M salzsaurer Lösung nicht reduziert. Das Gesamt-Sb wird in einem Aliquot der Probelösung bestimmt, das dazu mit HCl bis zur 6fachen Molarität versetzt wird. Der DPV-Bereich wird von –0,5 bis –0,1 V ausgenützt (E _p f:ur Sb(V) und Sb(III) ist –0,30 V). Das Verfahren wurde für Gläser verschiedenster Zusammensetzung angewendet. Die Ergebnisse wurden mit den Resultaten der Spektrophotometrie und der coulometrischen Titration verglichen.

---

---

Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

Titrimetric determination of silver,chloride and bromide in glasses

Titrimetric methods are described for the determination of total silver, free silver or free halide (Cl, Br and I), and bromide (or iodide) in glasses. Total silver is titrated potentiometrically with standard bromide solution after hydrofluoric—sulfuric acid sample decomposition followed by sodium hydrogensulfate fusion for volatilizing hydrogen halide. Free silver is determined similarly on a separate sample without the fusion step. For glasses containing excess of halide, free halide is titrated potentiometrically with standard silver(I) solution after dissolution of the sample in ice-cold hydrofluoric—nitric acid. Total bromide (or iodide) is determined by iodometric titration after oxidation to bromate (or iodate) with hypochlorite solution. The methods have been applied to a wide range of complex glass compositions and results are compared with values obtained by controlled-potential coulometry and x-ray fluorescence analysis.     

Chiral coordination polymer as a luminescence sensor for small organic molecules

1. Download high-res image (178KB)
2. Download full-size image

     

Itosides A – I,New Phenolic Glycosides from Itoa orientalis

Eight new benzoylated gentisyl alcohol (=2‐(hydroxymethyl)benzene‐1,4‐diol) glucosides, itosides A–H ( 1 – 8 ), together with the new pyrocatechol (=benzene‐1,2‐diol) glycoside itoside I ( 9 ) were isolated from the bark and twigs of Itoa orientalis (Flacourtiaceae). In itosides B–D ( 2 – 4 ), the gentisyl alcohol moiety was esterified by 1‐hydroxy‐6‐oxocyclohex‐2‐ene‐1‐carboxylic acid, while itosides E–H ( 5 – 8 ) contained instead an additional 2‐hydroxybenzoic acid moiety. The compounds were accompanied by the known derivatives 4‐hydroxytremulacin ( 10 ), poliothyrsoside ( 11 ), poliothyrsin ( 12 ), homaloside D ( 13 ), tremulacin, and pyrocatechol β‐D ‐glucopyranoside. The structures of the new compounds were elucidated by spectral and chemical methods.     

Stabilities in field electron emissions from noble‐metal covered W nano‐tips: apex structure dependence

We observed field emission microscopy (FEM) patterns of noble‐metal (NM) covered W nano‐tips with three different apex structures fabricated by field evaporation. Each of the three tips was terminated with a single atom, three atoms or ten atoms. We investigated the temporal changes in the FEM of these tips to discuss the stabilities in the spatial distributions of the field emission (FE) beams. The single‐atom tip showed two characteristics that were superior to the others. First, the beams emitted from the single‐atom tip were the most collimated among the three tips (the semi‐cone angle of 1.0° , FWHM). Second, adsorption of residual gas had little influence on FE from the single‐atom tip, while the other tips were easily contaminated even at ultra high vacuum, resulting in the emission fluctuation. Copyright © 2006 John Wiley & Sons, Ltd.     

Kinetic parameters from thermogravimetric study of used rubber granulates–polyurethane composites

From the TG data of rubber granulates, different polyurethane and composites it can be seen that the thermal decomposition for the rubber granulate and all of the composites start above 520 K. Two major mass losses for the rubber granulates and majority of the composites were observed and thermal decomposition is essentially complete by ~820 K. The changes of activation energies of lower and higher temperature decomposition, calculated according to the different equations were observed for a priori assumed first-order reaction for devolatilisation. Differences between determined and calculated results could suggest a possible reaction between polyurethane agents and rubber granulate during the composites formations.     

TEXTURE AND CRYSTALLINITY EVOLUTION IN ISOTACTIC POLYPROPYLENE INDUCED BY ROLLING AND THEIR INFLUENCE ON MECHANICAL PROPERTIES

The orientation and crystallinity evolution of isotactic polypropylene （iPP） induced by rolling were studied using wide angle X-ray scattering with an area detector. The tensile mechanical properties of rolled isotactic polypropylene sheets were also measured in this work. The texture component method was used to analyze the rolling texture. The rolling texture consists mainly of （010）[001], （130）[001] and [001]//RD fiber components in the sample with a rolling true strain of 1.5. The results reveal that crystallinity drastically decreases during rolling. It is suggested that amorphization is a deformation mechanism which takes place as an alternative to crystallographic intralamellar slip depending on the orientation of the lamellae. Both the orientation and crystallinity affect the tensile mechanical properties of rolled polypropylene. Crystallinity influences the elastic modulus on both directions and yield strength on transverse direction at the first stage of deformation. Orientation is the main reason for the changes of mechanical properties, especially at the latter part of deformation. The changes of both tensile strength and elongation percentage on rolling direction are larger than those on transverse direction, which results from the orientation. At last, the anisotropic mechanical properties occur on the rolling and transverse direction： high tensile strength with low elongation percentage on rolling direction and low tensile strength with high elongation percentage on transverse direction.     

碳纳米管在接枝二元胺过程中微结构的变化

通过对酸化的多壁碳纳米管(MWNTs)进行酰氯化, 在碳纳米管表面接枝己二胺. 用红外光谱、热重分析、拉曼光谱和场发射扫描电镜对处理前后的碳纳米管进行分析表征. 结果表明, 经过酰氯活化, 己二胺比较容易被接枝到碳纳米管上. 而且还发现碳纳米管在酸化后形成紧密块状结构, 在接枝胺后重新变得蓬松, 其表观比容甚至大于原始碳纳米管. 从理论上分析了碳纳米管的反应过程, 对碳纳米管在接枝胺过程中微结构的变化机理进行推测, 认为通过接枝, 己二胺插入碳纳米管之间, 改变了碳纳米管之间的相互作用, 使得酸化后因形成氢键而导致的紧密堆砌结构被破坏.     

16-脱氢孕烯醇酮醋酸酯的环境友好合成法

Instead of environmentally toxic chromium oxidant, singlet oxygen generated photcchemically was used as environmentally friendly and benign oxidizing agent to accomplish the transformation of pseudodiosgenin diacetate to diosone efficiently in a low toxic and less expensive solvent acetone. Accordingly 16-dehydropregnenolone acetate(16-DPA), an important intermediate for preparation of steroidal drugs, was prepared in good yield (75%) when photoreaction was run in acetone/acetic anhydride/pyridine system. The mild reaction condition as well as simple and environmentally friendly process made the method commercially viable and important for production of 16-DPA in industrial scale.