Two-dimensional imaging of atomic distribution morphology created by holographically induced mass transfer of monomer molecules and nanoparticles in a silica-nanoparticle-dispersed photopolymer film

We report an electron-probe microanalysis of a hologram recorded in a silica-nanoparticle-dispersed photopolymer film. We used S and Si atoms as label elements to identify formed polymer and nanoparticle species, respectively. It is found that the periodic density distributions of S and Si atoms are out of phase with each other, indicating that those of the formed polymer and nanoparticles are out of phase each other. This result shows decisive evidence of the mutual diffusion of monomer molecules and silica nanoparticles in the film under holographic two-beam interference exposure.     

Low-birefringent, chiral banana phase below calamitic nematic and/or smectic C phases in oxadiazole derivatives

Bent-shaped molecules based on the oxadiazole central core with various side wings and terminal chain groups have been synthesized, and their liquid-crystalline behavior was investigated by optical microscopic, X-ray, and electrooptic measurements. These molecules exhibit liquid-crystal polymorphism including both the calamitic and banana phases. Such a characteristic polymorphism is attributable to the larger bend angle of the oxadiazole core compared to that of the resorcinol core used in conventional banana molecules. Only one type of banana phase, designated as the Bx phase, is formed. It appears upon cooling from the nematic and smectic liquid crystals and exhibits chiral domains with a very weak birefringence (apparently optically isotropic). By applying an electric field, the Bx phase is altered to a high-birefringence B2 phase with a homochiral SmC(A)P(A) structure that exhibits an antiferroelectric response. From detailed analyses of the optical texture and X-ray patterns through the transformation from well-oriented calamitic phases, the Bx phase was found to exhibit a helical structure, which arises as a frustration from the ground-state B2 phase in such a manner that the blocks of B2 layers are twisted with respect to each other in a direction parallel to the layer plane similarly to the twisted grain boundary (TGB) phase.     

Reductive Rearrangement of Tetraphenyldiphosphine Disulfide To Trigger the Bisthiophosphinylation of Alkenes and Alkynes

The facile synthesis of organophosphorus compounds is of great importance for the development of new synthetic methods by using air-stable sources of phosphorus. In this respect, a synthetic method that is based on a reductive rearrangement and is capable of converting air-stable pentavalent phosphorus compounds into reactive trivalent phosphorus compounds is a powerful tool. Tetraphenyldiphosphine disulfide, which is a shelf-stable solid, was the focus of this study, and it was shown to undergo reductive rearrangement to trigger the bisthiophosphinylation of a variety of alkenes, such as terminal, cyclic, internal, and branched alkenes, 1,3-dienes, and terminal alkynes when exposed to light without any catalyst, base, or additive.     

Kinetic Monte Carlo simulation of nanoparticle film formation via nanocolloid drying

A kinetic Monte Carlo simulation of nanoparticle film formation via nanocolloid drying is presented. The proposed two-dimensional model addresses the dynamics of nanoparticles in the vertical plane of a drying nanocolloid film. The gas–liquid interface movement due to solvent evaporation was controlled by a time-dependent chemical potential, and the resultant particle dynamics including Brownian diffusion and aggregate growth were calculated. Simulations were performed at various Peclet numbers defined based on the rate ratio of solvent evaporation and nanoparticle diffusion. At high Peclet numbers, nanoparticles accumulated at the top layer of the liquid film and eventually formed a skin layer, causing the formation of a particulate film with a densely packed structure. At low Peclet numbers, enhanced particle diffusion led to significant particle aggregation in the bulk colloid, and the resulting film structure became highly porous. The simulated results showed some typical characteristics of a drying nanocolloid that had been reported experimentally. Finally, the potential of the model as well as the remaining challenges are discussed.     

Preparation of 2-Methoxy-3,4-methylenedioxybenzaldehyde (Croweacin Aldehyde) from Pyrogallol

2-Methoxy-3,4-methylenedioxybenzaldehyde (croweacin aldehyde) of high purity was prepared in 55% overall yield from pyrogallol.     

Preparation and properties of flexible free‐standing films via polyalkoxysiloxanes by acid‐catalyzed controlled hydrolytic polycondensation of tetraethoxysilane and tetramethoxysilane

Acid‐catalyzed controlled hydrolytic polycondensation of tetraethoxysilane (TEOS) and tetramethoxysilane (TMOS) provided polyalkoxysiloxanes PEOS and PMOS, with high molecular weight of 1100–12 000 or 2700–31 000, respectively. They were stable to self‐condensation, soluble in organic solvents, and especially characterized by high silica content of up to 62% (PEOS) and 72% (PMOS). Flexible and transparent free‐standing films with tensile strength of 1.6–5.2 MPa (PEOS) or 3.6–11.8 MPa (PMOS) were prepared by heating polyalkoxysilanes at 80°C for one to several days. They are also regarded to be a potential precursor for coatings and binders. Copyright © 2012 John Wiley & Sons, Ltd.