Effect of syndiotacticity on the aqueous poly(vinyl alcohol) gel 4. X-ray diffraction analysis of gel

Summary The structure of syndiotacticity-rich poly(vinyl alcohol) (PVA)-water gel was investigated by the X-ray diffraction analysis. Diffuse haloes appeared in the gel prepared from lower aqueous solution of PVA (5 wt%) but diffraction pattern became sharper with increasing concentration of PVA. Thed-spacings of gels and films are agreed with each other. The half height width of value of peak position of (101) obtained by photodensitometer decreased with increasing syndiotacticity of PVA. The radius of gyration of gel obtained from theGuinier's plots by the small angle X-ray diffraction increases with increasing syndiotacticity. These results suggest that the syndiotactic sequence length increases with increasing content of syndiotacticity and the crystallites in gel networks become also larger with increasing syndiotacticity. The average size of gel junction is 73–89 Å (s-(diad)% = 49.₄-66.₂).

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Zusammenfassung Es wurden mit Röntgeninterferenzen die Strukturen von einem Polyvinylalkohol-Wasser-Gel mit syndiotaktisch angereichertem Polyvinylalkohol untersucht. Es erscheinen diffuse Halos in dem Gel, das aus niedrigeren wäßrigen Lösungen (5% PVA) präpariert wurde. Doch wurden die Beugungsinterferenzen schärfer mit steigender Konzentration an PVA. Died-Abstände in Gelen und Filmen stimmten miteinander überein. Die Halbwertsbreite der 101-Interferenzen, gemessen mit einem Photodensitometer, nahm mit steigender Syndiotaktizitat des PVA ab. Der Trägheitsradius des Gels aus Guinier-Auftragungen für die Kleinwinkelstreuung nimmt mit steigender Syndiotaktizitat zu. Diese Ergebnisse legen nahe, daß die syndiotaktische Segmentläange mit steigendem Gehalt an Syndiotaktizitat zunimmt und daß die Kristallite in den Gelnetzwerken mit zunehmender Syndiotaktizität gröBer wurden. Die mittlere Größe des Netzwerkabstandes ist 73–89 Å (s-(diad)% = 49.₄-66.₂).

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With 7 figures in 15 details and 3 tables     

Quantitative analysis of ethanol–methanol–water ternary solutions using Raman spectroscopy

Raman spectroscopy was used for rapid in-situ measurement of alcohols in ethanol-methanol-water ternary systems. Mass fractions of the individual components were determined using calibration curves for binary systems of ethanol-water, methanol-water, and ethanol-methanol. Calibration curves were constructed by calculating the ratio of the Raman peak intensity of a component and that of an external standard (acetonitrile). Assuming additivity of the spectra, simultaneous equations were written, and mass fractions of ethanol, methanol, and water in the ternary solutions were determined by solving the system of equations through calculating an inverse matrix. The relative errors between the mass fractions obtained from the Raman spectra and those obtained from mass measurements were <0.6%.     

Local structural analysis of In-doped Bi2Se3 topological insulator using X-ray fluorescence holography

We performed X-ray fluorescence holography measurements on an In-doped Bi₂Se₃ topological insulator and obtained an in-plane atomic image in the vicinity of In. We found that atomic images at the positions of the first nearest neighbors (NNs) are very weak whereas those at the positions of the second and the third NNs are relatively strong. On the basis of the fact that In is half of the atomic number of Bi, we attributed the origin of this feature to the clustering of the In atoms in the Bi plane. We calculated the intensity of the atomic images and confirmed that the formation of In cluster results in a decrease by 30% in the first NN atomic image intensity. However, the decrease in the magnitude is not enough to explain the experimental results, suggesting another contribution such as the lattice distortions. The effect of the lattice distortion on the atomic image intensity is discussed on the basis of the simulation including the positional fluctuation of In atoms.     

Neutron activation analysis of carbonate reference materials: coral (JCp-1) and giant clam (JCt-1)

Journal of Radioanalytical and Nuclear Chemistry - Two kinds of carbonate reference materials, coral (JCp-1) and giant clam (JCt-1), were subjected to neutron activation analysis (NAA) using the...     

Formation of an Azaruthenacyclopentadiene Skeleton via Ammonia Activation by an Electron-Deficient Ru3 Cluster

A dicationic triruthenium complex containing a μ₃-η³-C₃ ring, [(Cp*Ru)₃(μ₃-η³-C₃MeH₂−)(μ₃-CH)(μ-H)]²⁺ ( 1 a , Cp*=η⁵-C₅Me₅), reacted with ammonia to yield a μ-amido complex, [(Cp*Ru)₃(μ₃-η³-CHCMeCH) (μ₃-CH)(μ-NH₂)]²⁺ ( 5 ), via N−H bond scission. Subsequent treatment with base resulted in C−N bond formation to yield a μ₃-η²:η²-1-azabutadien-4-yl complex, [(Cp*Ru)₃(μ₃-CH)(μ₃-η²:η²-NH=CH−CMe=CH−)]⁺ ( 6 a ). The azaruthenacyclopentadiene skeleton was alternatively synthesized by the photolysis of mono-cationic complex [(Cp*Ru)₃(μ₃-η³-C₃RH₂−)(μ₃-CH)]⁺ ( 2 a ; R=Me, 2 b ; R=H) in the presence of ammonia. The C₃ ring skeleton was broken via the electron transfer to the π*(C−C) orbital in the C₃ ring, and a transiently generated unsaturated μ₃-allylic species can take up ammonia, resulting in N−H bond scission followed by C−N bond formation.     

Photoinduced Betaine Generation for Efficient Photothermal Energy Conversion

The conversion of solar energy to thermal, chemical, or electrical energy attracts great attention in chemistry and physics. There has been a considerable effort for the efficient extraction of photons throughout the entire solar spectrum. In this work light energy was efficiently harvested by using a long-lived betaine photogenerated from an acridinium-based electron donor–acceptor dyad. The photothermal energy-conversion efficiency of the dyad is significantly enhanced by simultaneous illumination with blue (420–440 nm) and yellow (>480 nm) light in comparison with the sum of the conversion efficiencies for individual illumination with blue or yellow light. The enhanced photothermal effect is due to the photogenerated betaine, which absorbs longer-wavelength light than the dyad, and thus the dyad–betaine combination is promising for efficient photothermal energy conversion. The mechanisms of betaine generation and energy conversion are discussed on the basis of steady-state and transient spectral measurements.