Viscoelastic and structural properties of a phenyl-modified polysiloxane system with a three-dimensional structure

The relationships between the viscoelastic and structural properties of glass-forming materials with polysiloxane bonds, which serve as network formers, and phenyl groups, which act as network terminators, are examined based on shear viscoelasticity, (29)Si MAS NMR, and GPC measurements during the early stages of the network-forming process. The viscosities of the present samples do not depend on the frequency at temperatures up to 200 degrees C, suggesting that the origin of the viscous flow does not include intermolecular entanglement. According to the results of the strain dependence of the elastic modulus, the bridging-oxygen number, and molecular weight, the present polysiloxane system has a complex structure, or distribution of various-sized molecules composed of a polysiloxane network with various dimensionalities, and furthermore an elementary process of the viscosity is simple flow of these molecules. The structural factors that determine the viscosity and its temperature dependence are categorized into the molecular size and the intramolecular structure by using a theory based on the free-volume model. The relationship between the viscosity and the structure around the glass transition temperature is quantitatively examined and it is concluded that introducing larger numbers of Ph groups makes the viscosity less sensitive to structural factors.     

Facile synthesis of [1]benzothieno[3,2-b]benzothiophene from o-dihalostilbenes

A convenient one-pot synthesis of [1]benzothieno[3,2-b]benzothiophene from readily available o-dihalostilbenes using combined reagents of sodium sulfide nonahydrate (Na₂S·9H₂O) or sodium hydrosulfide hydrate (NaSH·nH₂O) and sulfur is described along with plausible reaction paths in this intriguing reaction.     

Applanatines A-E from the culture broth of Ganoderma applanatum

Five novel compounds, applanatines A-E (1-5), and a known one (6) were isolated from the culture broth of Ganoderma applanatum. Their structures including the relative configurations were determined by the interpretation of spectroscopic data. Compounds 3 and 4 suppressed the growth of Fusobacterium nucleatum, that is, a prominent member of the oral microflora implicated in periodontitis.     

Au-assisted visible laser MALDI

The excitation of UV-absorbing MALDI matrixes with visible laser (532 nm wavelength) and the desorption/ionization of biomolecules were performed by coating the analytes doped matrix with Au thin film (5–10 nm) using ion sputtering deposition. The Au film was first ablated with the laser of higher fluence, resulting in a crater/hole about the size of the laser beam spot on the target. After a few initial laser shots, analytes and matrix related ions were observed from the crater even at lower laser fluence. Electron microscopy inspection on the laser ablated region revealed the formation of nanoparticles with sizes ranging from <10 to 50 nm. Compared with the infra-red laser (1064 nm) excitation, the visible laser produced much higher abundance of matrix radical ions, and less heating effect as measured by the thermometer molecules. The results suggest the photo-excitation and photo-ionization of matrix molecules by the visible laser, possibly assisted by the gold nanoparticles and nanostructures left on the ablated crater.     

Hydrogen Storage Mediated by Pd and Pt Nanoparticles

The hydrogen storage properties of metal nanoparticles change with particle size. For example, in a palladium–hydrogen system, the hydrogen solubility and equilibrium pressure for the formation of palladium hydride decrease with a decrease in the particle size, whereas hydrogen solubility in nanoparticles of platinum, in which hydrogen cannot be stored in the bulk state, increases. Systematic studies of hydrogen storage in Pd and Pt nanoparticles have clarified the origins of these nanosize effects. We found a novel hydrogen absorption site in the hetero‐interface that forms between the Pd core and Pt shell of the Pd/Pt core/shell‐type bimetallic nanoparticles. It is proposed that the potential formed in the hetero‐interface stabilizes hydrogen atoms rather than interstitials in the Pd core and Pt shells. These results suggest that metal nanoparticles a few nanometers in size can act as a new type of hydrogen storage medium. Based on knowledge of the nanosize effects, we discuss how hydrogen storage media can be designed for improvement of the conditions of hydrogen storage.     

Membrane Preparation of Polysulfonic Acid Complexes by Layer-by-Layer Adsorption

Summary: The water-insoluble, thermostable and homogeneous polymer complex membrane formation of polysulfonic acids was examined by modifying the preparation conditions of the layer-by-layer adsorption method of the acid and base polymers. The complexation of poly(4-styrenesulfonic acid) in the 0.15 unit mM solution with poly(allylamine) gave a polymer complex membrane on a gold substrate in which one polymer layer was formed with a thickness of 1 nm. Properties including the proton conductivity of the membrane suggested possible applications of the polymer complex membrane.