Phase behavior and rheology of oil-swollen micellar cubic phase and gel emulsions in nonionic surfactant systems

We have studied the phase behavior and rheological property of the cubic phase and related gel emulsions in water/nonionic/dodecane systems. In the phase behavior study, it is pointed out that the formation of the discontinuous cubic phase (I₁) is not common in all nonionic surfactant systems; however, a cubic phase (I₁) with oil-swollen micelles or a cubic phase microemulsion is found in the water/C₁₆EO₆/dodecane system, which can solubilize large amount of oil. It was also observed that water/C₁₆EO₆/dodecane system forms stable gel emulsion. In the rheological study we have found an anomalous behavior of the I₁ phase in the water/C₁₂EO₆/dodecane and the water/C₁₆EO₆/dodecane systems. In the water/C₁₂EO₆/dodecane system, the viscoelastic nature of the I₁ phase has been observed, which is shifted to the elastic nature with the addition of dodecane, whereas, highly elastic nature was observed in the water/C₁₆EO₆/dodecane system. In both the cases shear-thinning behavior were seen. The elastic modulus, G′ and complex viscosity, |η1| of the I₁ phase increase with the dodecane concentration in the water/C₁₂EO₆/dodecane system, whereas, decreasing trend have been observed in the water/C₁₆EO₆/dodecane system. This anomalous behavior is suggested due to the nonspherical shape of micelles or polydispersity of the micelles in the water/C₁₆EO₆/dodecane system. The rheological behavior of the O/I₁ gel emulsion was also studied in both the systems.     

Formation of a highly ordered dot array of surface micelles of a block copolymer via liquid crystal-hybridized self-assembly

A highly ordered dot array pattern of surface micelles on water is formed by a spread monolayer of an amphiphilic block copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-4VP), via hybridization with a liquid crystal molecule, 4'-pentyl-4-cyanobiphenyl (5CB), on water. Simple co-spreading of PS-4VP with 5CB provides a flat homogeneous monolayer of PS-4VP on water without the aggregation of PS blocks. With increasing surface pressure, well-defined dots of the PS blocks start to grow and are arrayed in a highly ordered hexagonal structure. The exact coincidence of the surface pressure-area curves for the hybrid monolayer in the compression and expansion processes confirms that the flat spread monolayer and the dot array are formed on water in the equilibrium state by a self-assembly process.     

Thioridazine induces immediate and delayed erythema in photopatch test

Thioridazine is a phenothiazine derivative that has been used as an antipsychotic; it rarely causes photosensitization. However, we noticed that this drug induced an erythematous reaction in a photopatch test. Six volunteers were patch tested with various concentrations of thioridazine and irradiated with a range of UVA doses, and the time courses of the color of and blood flow to the test sites were monitored. The free-radical metabolites of thioridazine generated under UVA irradiation and its effects on ascorbate radical formation were examined with an electron paramagnetic resonance (EPR) spectrometer in vitro. As a result, immediate erythema developed during UVA irradiation in most subjects when 1% thioridazine was applied for 48 h and irradiation doses were higher than 4 J cm(-2). Another peak of erythematous reaction was observed 8-12 h after irradiation. The in vitro examination detected an apparent EPR signal, which appeared when 2 mM thioridazine in air-saturated phosphate buffer was irradiated with UVA, whereas this reaction was attenuated under anaerobic conditions. The EPR signal of the ascorbate radical was augmented under both aerobic and anaerobic conditions. Thioridazine-derived oxidants and/or thioridazine radicals generated during UVA irradiation seem to play an important role in this unique phototoxic reaction.     

Structures and phase transition of multi-layered water nanotube confined to nanochannels

We placed nanometer-scale water-tube clusters with phase transition within a porous crystal formed from molecular blocks specifically designed to investigate the molecular dynamics of confined water molecules.     

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.