Redox reaction of disulfide polyaniline in aqueous solution

The cleavage and formation of the di sulfide bond of 2,5-dimercapto-1,3,4-thiadiazole (DMcT) were examined in an aqueous solution of pH value from 0 to 14 with and without polyaniline (PAn), The redox reaction of DMcT was accelerated by PAn in acidic condition. The cell using this anodic material was set-up and characterized in aqueous electrolyte.

The suppression of Ge-132 on the Maillard reaction of BSA by fluorescence spectrum

The fluorescences of BSA and glycosylated BSA were observed respectively. The lambda(cm) of BSA was 340 nm; while the lambda(cm) of glycosylated BSA was 436 nm. Because the fluorescence spectra of them were different greatly, we can observe the suppression of Ge-132 on the Maillard reaction of BSA without any interference of itself. It was showed that the fluorescence intensity of glycosylated BSA increased continuously with the cultured time, Ge-132 may suppress the Maillard reaction of BSA greatly, and the suppressing efficicency would be 32 %. The key site of the Maillard reaction of BSA is free amino groups of alanine residues on N-terminal amino group, besides the epsilon-amino groups of intrachain Lysine residues.

The characterization of the interfacial reaction in polyamide 1010 poly(propylene)-graft-(glycidylmethacrylate) blends

Binary blends of polyamide 1010/poly(propylene) and polyamide 1010 (PA1010)/poly(propylene)-graft-(glycidyl methacrylate) (PP-g-GMA) were prepared. The epoxy groups in PP-g-GMA react with the amino end-groups in PA1010, thus a PA1010-graft-PP copolymer is formed and acts as a compatibilizer between PA1010 and PP-g-GMA. The reaction was confirmed by electron spectroscopy for chemical analysis (ESCA) and attenuated total reflection (ATR)-FTIR spectroscopic analysis, and also evaluated by the stability of the suspension obtained by dissolving the blends in formic acid and by the morphologies of the blends.

Reaction of halfsandwich iridium polychalcogenide complexes with dimethyl acetylenedicarboxylate. Molecular structure of Cp*Ir[S2C2(COOMe)(2)]

The pentamethylcyclopentadienyl iridium complexes Cp*Ir(PMe3)(E-n) (E = S, n = 4, 5 or 6; E = Se, n = 2 or 4 E = Te, n = 2) react with dimethyl acetylenedicarboxylate to give Cp*Ir(PMe3)[E2C2(COOMe)(2)] compounds which tend to lose the trimethylphosphine ligand; the molecular structure of the dithiolene derivative, Cp*Ir[S2C2(COOMe)(2)], has been determined.

Studies on the product of ion-molecule reaction of halogeno-benzene in gas phase by MS/MS

The fragmentations of the product ions produced by the ion-molecule reaction of the halogeno-benzene (chlorobenzene, bromobenzene and iodobenzene) were studied using the collision-induced dissociation, The main product ions of the ion-molecule reaction of three kinds of halogeno-beneze include the dimeric ions, m/z(2M-X) ions and m/z(2M-2X) ions, The CID spectra of these ions were compared with that of the protonated bromodiphenyl and biphenyl, The formation mechanism and the structure of the product ions were obtained.

High resolution solid-state NMR and DSC study of poly(ethylene glycol) silicate hybrid materials via sol-gel process

Hybrid materials incorporating poly(ethylene glycol) (PEG) with tetraethoxysilane (TEOS) via a sol-gel process were studied for a wide range of compositions of PEG by DSC and high resolution solid-state C-13- and Si-29-NMR spectroscopy. The results indicate that the microstructure of the hybrid materials and the crystallization behavior of PEG in hybrids strongly depend on the relative content of PEG. With an increasing content of PEG, the microstructure of hybrid materials changes a lot, from intimate mixing to macrophase separation. It is found that the glass transition temperatures (T-g) (around 373 K) of PEG homogeneously embedded in a silica network are much higher than that (about 223 K) of pure PEG and also much higher in melting temperatures T-m (around 323 K) than PEG crystallites in heterogeneous hybrids. Meanwhile, the lower the PEG content, the more perfect the silica network, and the higher the T-g of PEG embedded in hybrids. An extended-chain structure of PEG was supposed to be responsible for the unusually high T-g of PEG. Homogeneous PEG-TEOS hybrids on a molecular level can be obtained provided that the PEG. content in the hybrids is less than 30% by weight. (C) 1998 John Wiley & Sons, Inc.

REACTION OF METHANE WITH CARBON DIOXIDE OVER SrNiAl_(11)O_(19)

合成了六铝酸盐ＳｒＮｉＡｌ１１Ｏ１９并用ＸＲＤ、ＵＶＤＲＳ、ＴＧＤＴＡ和ＴＥＭ等技术对其进行了表征。在７５０℃于ＳｒＮｉＡｌ１１Ｏ１９上进行的甲烷与二氧化碳重整反应表明，这类催化剂较Ｎｉ／ＳｒＡｌ１２Ｏ１９具有较大活性和低积碳能力，在催化反应过程中可有效地抑制Ｎｉ颗粒的增大。

Electrochemical scanning tunneling microscopy and electrochemical quartz crystal microbalance study of the adsorption of phenanthraquinone accompanied by an electrochemical redox reaction on the Au electrode

In situ electrochemical scanning tunneling microscopy (ECSTM) and an electrochemical quartz crystal microbalance (EQCM) have been employed to follow the adsorption/desorption processes of phenanthraquinone (PQ sat. in 0.1 mol l(-1) HClO4, solution) accompanied with an electrochemical redox reaction on the Au electrode. The result shows that: (1) the reduced form PQH(2) adsorbed at the Au electrode and the desorption occurred when PQH(2) was oxidized to PQ; (2) the adsorption process initiates at steps or kinks which provide high active sites on the electrode surface for adsorption, and as the potential shifts to negative, a multilayer of PQH(2) may be formed at the Au electrode; (3) the reduced PQH(2) adsorbed preferentially in the area where the tip had been scanned continually; this result suggests that the tip induction may accelerate the adsorption of PQH(2) on the Au(111) electrode. Two kinds of possible reason have been discussed; (4) high resolution STM images show the strong substrate lattice information and the weak monolayer adsorbate lattice information simultaneously. The PQH(2) molecules pack into a not perfectly ordered condensed physisorbed layer at potentials of 0.1 and 0.2 V with an average lattice constant a = 11.5 +/- 0.4 Angstrom, b = 11.5 +/- 0.4 Angstrom, and gamma = 120 +/- 2 degrees; the molecular lattice is rotated with respect to the substrate lattice by about 23 +/- 2 degrees. (C) 1997 Elsevier Science S.A.

Cure processing modeling and cure cycle simulation of epoxy-terminated poly(phenylene ether ketone) .1. DSC characterization of curing reaction

The curing reaction process of epoxy-terminated poly(phenylene ether ketone) (E-PEK) with 4,4'-diaminodiphenyl sulfone (DDS) and hexahydrophthalic acid anhydride (Nadic) as curing agents was investigated using isothermal differential scanning calorimetry (IDSC) and nonisothermal differential scanning calorimetry (DDSC) techniques. It was found that the curing reactions of E-PEK/DDS and E-PEK/Nadic are nth-order reactions but not autoaccelerating. The experimental results revealed that the curing reaction kinetics parameters measured from IDSC and DDSC are not equivalent. This means that, in the curing reaction kinetics model for our E-PEK system, both isothermal and nonisothermal reaction kinetics parameters are needed to describe isothermal and nonisothermal curing processes, The isothermal and nonisothermal curing processes were successfully simulated using this model. A new extrapolation method was suggested. On the basis of this method the maximum extent of the curing reaction (A(ult)) that is able to reach a certain temperature can be predicted. The A(ult) for the E-PEK system estimated by the new method agrees well with the results obtained from another procedure reported in the literature. (C) 1997 John Wiley & Sons, Inc.

Characterization and catalytic behavior of La2-x(Sr,Th)(x)CuO4+/-lambda in reaction NO+CO

Two mixed oxide systems La2-xSrxCuO4+/-lambda(0.0 less than or equal to x less than or equal to 1.0) and La2+xThxCuO4+/-lambda(0.0 less than or equal to x less than or equal to 0.4) with K2NiF4 structure were prepared by varying re values; Their crystal structures were studied by means of XRD and IR spectra. The average valence of Cu ion at B site, nonstoichiometric oxygen (A) and the chemical composition in the bulk and on the surface of the catalysts were measured by means of chemical analysis and XPS. The catalytic behavior in reaction CO + NO was investigated under the regular change of average valence of Cu ion at B site and nonstoichiometric oxygen (lambda). Meanwhile, the adsorption and activation of the small molecules NO and the mixture of NO + CO over the mixed oxide catalysts were studied by means of MS-TPD. The catalytic mechanism of reaction NO + CO over these oxide catalysts were proposed; and it has been found that, at lower temperatures the activation of NO is the rate determining step and the catalytic activity is related to the lower valent metallic ion and its concentration, while at higher temperatures the adsorption of NO is the rate determining step and the catalytic activity is related to the oxygen vacancy and its concentration.

Studies of catalyzed reaction mechanism between co-polyether (THF/EO) and N-100 by NMR - Interaction and complex formation between reactants and catalysts

To elucidate the mechanism of the catalyzed reaction of co-polyether (EO/THF) with N-100, the interaction and complex formation between reactants and catalysts were investigated by means of NMR spectroscopy. It is shown that the resonance peak of isocyanate carbon splits into two parts when the solutions of N-100 and co-polyether were mixed. The disappearing of proton resonance peak of hydroxyl group in NMR spectra when dibutyltin dilaurate(DBTDL) were added to the copolyether(THF/EO) solution indicates the complex formation, This interaction appears to be a bonding of tin to the oxygen of hydroxyl and make the hydrogen of the hydroxyl group very mobile and active, then exchange with other protons, In the case of triphenyl bismuth(TPB), the high field shift and intensity enhancement of proton peak were observed, which suggest a nucleophilic attack of the bismuth to the hydroxyl hydrogen.

Catalytic mechanisms of triphenyl bismuth, dibutyltin dilaurate, and their combination in polyurethane-forming reaction

The catalytic mechanisms of triphenyl bismuth (TPB), dibutyltin dilaurate (DBTDL) and their combination have been studied in a model polyurethane reaction system consisting of copolyether (tetrahydrofuran-ethyleneoxide) and N-100; NMR spectroscopy was used to detect the associations between reactants and catalysts. A relatively stable complex was shown to be formed between hydroxyl and isocyanate; the catalysts showed different effects on the isocyanate-hydroxyl complex, therefore resulting in different curing characteristics. The formation of hydrogen bonding between the complexed hydroxyl and other hydroxyl or the resulting urethane provided an ''auto-catalysis'' to urethane formation. DBTDL destroyed the isocyanate-hydroxyl complex before catalyzing the reaction through the formation of a ternary complex, whereas TPB was able to activate the isocyanate-hydroxyl complex directly to form urethane. The reaction catalyzed by the combination of TPB and DBTDL gained advantages from the multiple catalytic entities, i.e., TPB, DBTDL, and a TPB-DBTDL complex. (C) 1997 John Wiley & Sons, Inc.

Formation of heterocyclic C-60 derivative by gas-phase ion/molecule reaction

Ion/molecule reactions of C-60 with vinyl acetate under chemical ionization conditions have been studied here. Compared with C2H3O+ from acetone, C2H3O+ from vinyl acetate undergoes the reactions more easily, a new heterocycle between C-60 and the studied ion is formed The generation of two sigma-bonds and little angle tensile force of pentatomic ring make it more stable.

Iron(II)-8-quinolinol/MCM-41-catalyzed phenol hydroxylation and reaction mechanism

Iron(II)-8-quinolino/MCM-41 is prepared. Its catalysis is studied in phenol hydroxylation using H2O2 (30%) as oxidant. The experiment shows that Iron(II)-8-quinolinol/MCM-41 has good catalytic activity and desired stability. Based on cyclic voltammetry, ESR, and UV-visible spectra studies of iron(II)-8-quinolinol complex in liquid phase, a radical substitution mechanism is proposed and used to demonstrate the experimental facts clearly. (C) 1997 Academic Press.