Rheology of self-assembled monolayers on solid-liquid interface oscillating at MHz frequency

The rheology properties (viscosity and elasticity) of chemisorbed soft matters on a solid-liquid interface oscillating at MHz were investigated using a quartz crystal microbalance (QCM). As a chemisorbed soft matter, we employed the self-assembled monolayers (SAMs) of mercapto oligo(ethylene oxide) methyl ethers, HS(CH₂CH₂O)_nCH₃ (n?=?5, 11, 12, 19, 27, 35 and 43), where those molecular weights had unity. The systematical analyses on the basis of the Voight model revealed the relationships of $\eta \propto M_n^{0.180}$ and $\mu \propto M_n^{0.344}$, where η and μ are the viscosity and elasticity of the SAM, and M_n is the molecular weight of HS(CH₂CH₂O)_nCH₃. As a result, we found that the SAM consisting of the oligomer followed the formula of polymer.     

Direct Carboxylation of Electron-Rich Heteroarenes Promoted by LiO-tBu with CsF and [18]Crown-6

We herein demonstrate that the combination of LiO-tBu, CsF, and [18]crown-6 efficiently promotes the direct C−H carboxylation of electron-rich heteroarenes (benzothiophene, thiophene, benzofuran, and furan derivatives). A variety of functional groups, including methyl, methoxy, halo, cyano, amide, and keto moieties, are compatible with this system. The reaction proceeds via the formation of a tert-butyl carbonate species.     

Control of nitrogen doping in NaTaO3 synthesized by hydrothermal reaction and chemical state of nitrogen

Nitrogen-doped NaTaO₃ was synthesized through 1-pot reaction, hydrothermal process using Ta₃N₅ as precursor. Changing concentration and amount of NaOH aqueous solution influenced nitrogen content in NaTaO₃. Absorption edge of nitrogen-doped NaTaO₃ was extended at 570 nm, and absorbance in visible light region depended on nitrogen content in NaTaO₃. Anodic photocurrent measured under visible light irradiation became larger with increasing nitrogen content in NaTaO_3-xN_y. Under ultraviolet light irradiation (λ ≤ 400 nm), the highest anodic photocurrent was observed when nitrogen concentration was y = 0.024. It was possible to expand the wavelength range that can be effectively utilized for the photoelectrochemical reaction.     

Two‐dimensional correlation gel permeation chromatography study of aggregate–aggregate interactions during acid‐catalyzed polymerization of triethoxysilyl‐terminated polystyrene

The three‐step polymerization of a well‐defined polymeric silane coupling agent, triethoxysilyl‐terminated polystyrene, catalyzed by acid (H₃PO₄), was traced as a function of the reaction time with gel permeation chromatography (GPC). Time‐resolved GPC traces collected during the polymerization process were then used to construct two‐dimensional (2D) correlation maps via generalized 2D correlation analysis. The results demonstrated that the synchronous and asynchronous 2D correlation GPC spectra directly reflected the dynamic variation of aggregate–aggregate interactions during each step of the polymerization. In particular, it was found that the formation of aggregates among the cyclic trimers (or tetramers) and monomers was critical for the preferential production of pentamers in the reaction system. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3447–3460, 2004     

On the fundamental group of the complement¶of certain affine hypersurfaces

Let and be two non-constant weighted homogeneous polynomials. Suppose that f and g are not powers of polynomials. Let p and q be two positive integers. In this paper, we calculate the fundamental group of the complement of the affine hypersurface in . In particular, we prove that the fundamental group is determined by p and q. Received: 29 January 1998     

An improved method for the measurement of the isotope ratio of ethanol in various samples, including alcoholic and non-alcoholic beverages

The isotope ratios of ethanol, an important constituent or ingredient of some foods and various beverages and fuels, provide information about biological and geographical origin and quality. We have developed an improved method for measuring the isotope ratio of ethanol in various samples by gas chromatography-high temperature conversion or combustion-isotope ratio mass spectrometry (GC-TC/C-IRMS) with headspace solid-phase microextraction (HS-SPME). A HS-SPME method was developed by optimizing several different parameters, including salt addition, incubation temperature and time, and extraction time. The HS-SPME method enabled us to determine the isotope ratio at low ethanol concentrations (0.08 mM) in 50 min with good precision (+/-0.3 per thousand for delta(13)C and +/-5 per thousand for deltaD). An advantage of this technique is that it can be adapted for use with samples which have high viscosity and contain many matrix compounds, such as alcoholic and non-alcoholic beverages.     

Syntheses, crystal structures and Si solubilities of new layered carbides Zr2Al4C5 and Zr3Al4C6

Two types of new ternary carbides, Zr₂Al₄C₅ and Zr₃Al₄C₆, have been synthesized and characterized by X-ray powder diffraction. The crystal structures were refined from laboratory X-ray powder diffraction data (CuKα₁) using the Rietveld method. These carbides form a homologous series with the general formula (ZrC)_mAl₄C₃ (m=2 and 3). The crystal structures can be regarded as intergrowth structures where the Al₄C₃-type [Al₄C₄] layers are the same, while the NaCl-type [Zr_mC_m+1] layers increase in thickness with increasing m value. The new carbides are most probably the end members of continuous solid-solutions (ZrC)_m[Al_4−xSi_x]C₃ with 0?x?0.44.     

Two iron-containing tungstogermanates: [K(H2O)(beta-Fe2GeW10O37(OH))(gamma-GeW10O36)]12- and [{beta-Fe2GeW10O37(OH)2}2]12-

Interaction of the dilacunary polyanion precursor [gamma-GeW(10)O(36)](8-) with Fe(3+) ions in aqueous buffer medium (pH 4.8) results in the formation of two dimeric tungstogermanates depending on the reactant ratios. When using an Fe3+ to [gamma-GeW(10)O(36)](8-) ratio of 1:1, the asymmetric anion [K(H(2)O)(beta-Fe(2)GeW(10)O(37)(OH))(gamma-GeW(10)O(36))](12-) (1) is formed, whereas [{beta-Fe(2)GeW(10)O(37)(OH)2}2]12- (2) is formed when using a ratio of 2:1. Single-crystal X-ray analyses were carried out on Cs(3)K(9)[K(H(2)O)(beta-Fe(2)GeW(10)O(37)(OH))(gamma-GeW(10)O(36))].19H(2)O (CsK-1), which crystallizes in the triclinic system, space group P1, a = 11.4547(2), b = 19.9181(5), c = 21.0781(6) A, alpha = 66.7977(12), beta = 89.1061(12), gamma = 84.4457(11) degrees, and Z = 2 and on Cs(7)K(4)Na[{beta-Fe(2)GeW(10)O(37)(OH)(2)}(2)].39H(2)O (CsKNa-2), which crystallizes in the monoclinic system, space group C2/m, a = 32.7569(13), b = 12.2631(5), c = 14.2895(5) A, beta = 104.135(2) degrees , and Z = 2. Polyanion 1 consists of (beta-Fe(2)GeW(10)O(37)) and (gamma-GeW(10)O(36)) units linked via two Fe-O-W bridges and a central potassium ion. Two equivalent FeO(6) octahedra complete the belt of the beta-Keggin unit and link to the (gamma-GeW(10)O(36)) fragment. On the other hand, 2 consists of two {beta-Fe(2)GeW(10)O(37)(OH)(2)} units with four bridging hydroxo groups linking the four Fe(3+) ions, forming an eight-membered ring. The magnetic properties of CsK-1 and CsKNa-2 have been studied by magnetic susceptibility and magnetization measurements and fitted according to an isotropic exchange model. Both polyanions 1 and 2 exhibit diamagnetic ground states with a small amount of paramagnetic impurity. Electrochemistry studies on 1 and 2 were carried out in a pH 5 acetate medium. The two polyanions have in common the simultaneous reduction of all of their Fe(3+) centers. This observation suggests the existence of identical or almost-identical influences on these centers and their equivalence, especially in the reduced state. Controlled potential coulometry results indicate the presence of two Fe(3+) centers in 1 and four in 2. The splitting of the tungsten wave of 1 compared to the single tungsten wave of 2 is attributed to a difference in acid-base properties of the polyanions. Voltammetric peak-potential shifts as a function of pH were studied in the case of 2.