Stabilization of hydrophobic domains in hydrogel by intermolecular hydrogen bonds between carboxylic groups at the distal end of alkyl side-chain

The role of intermolecular hydrogen bond on the stability of hydrophobically associated domains of hydrogel, consisting of 12-acryloyloxydodecanoic acid (ADA; hydrophobic) or 6-acryloyloxyhexanoic acid (AHA; hydrophobic) and acrylic acid (AA; hydrophilic), carrying an alkyl side group terminated by carboxylic acid, was studied by swelling behavior in an organic solvent/water mixture. We chose propionic acid (PAc) and 1-propanol (PrOH) as organic solvents whose solubility parameter, log P, logarithmic partition equilibrium coefficient for octanol/water, is similar. The equilibrated swelling ratio of poly(ADA-co-AA) and poly(AHA-co-AA) gels by PAc was higher than by PrOH at a lower composition (ca. 5–15 mol%) and that of homo-polymer poly(AHA) gel by PAc was higher even at a high composition (up to ca. 70 mol%). The variation in swelling with solvent/water composition indicated a cross-over between the two solvent systems and this phenomenon did not depend on the alkyl side-chain length. Using Fourier transfer infrared spectroscopy, we observed the remarkable shift of the wavelength corresponding to the hydrogen bond in PAc aqueous solutions. Non-dissociated short alkanoic acid, which can penetrate hydrophobic domains and form hydrogen bonds with non-dissociated carboxylic groups of the polymer gel, favors the disruption of hydrophobic domains, causing swelling. Intermolecular hydrogen bonds between carboxylic groups of the alkyl side-chain are thus closely involved in the stability of hydrophobic domains in copolymer gel.     

A Study on the Engineering Properties of Sand Improved by the Sand Compaction Pile Method

In order to directly evaluate the effects of soil improvement by the Sand Compaction Pile (SCP) method on the density, deformation, and static and liquefaction strength characteristics of sandy soils, a series of field and laboratory tests were performed. Laboratory tests were performed on high-quality undisturbed samples obtained from sandy soils both before and after soil improvement by the SCP method. The high-quality undisturbed samples were recovered by the in-situ freezing sampling method. The drained shear strength (internal friction angle, φ_d), liquefaction strength (R₁₅: cyclic stress ratio needed to cause 5% double amplitude axial strain in 15 cycles), and cyclic deformation characteristics (G~γ and h~γ relations) were determined by performing a series of laboratory tests on the undisturbed samples. Both the in-situ density and the relative density were measured on the undisturbed samples used in the laboratory tests. A standard penetration test (SPT) and a suspension-type P-S wave logging test were performed to investigate the soil profile of the test site before and after the sand compaction. Both the static and the liquefaction strengths of the sandy soils obtained in the laboratory tests were also compared with those estimated by empirical correlations used in practice based on the SPT N-value and soil gradations.     

Thermally Induced Behavior of the Openings in Rock Mass Affected by High Temperatures

The temporary storage of hot water in openings excavated in rock may be worthwhile for multiple land-use applications, environmental safeguards, and energy conservation. When used for hot water storage, the rock mass around the openings will respond by coupled thermomechanical effects induced by the hot water. In this study, a submergence test of granite and sandstone at 20 and 95°C was used to examine the thermal behavior of the rock mass around the openings to obtain the mechanical properties of uniaxial compressive strength and elastic modulus. A uniaxial compression creep test of the rock at high temperatures was also performed and calculations with various constants for the creep were examined. With the results obtained in this work, the temperature and stress distribution around the openings when hot water is stored was analyzed by considering the creep properties. The thermal behavior and stability of the openings were also examined. The displacement of the openings was predicted to be approximately 2% of the diameter after 1,000 days.     

Facile and scalable synthesis of a highly hydroxylated water-soluble fullerenol as a single nanoparticle

A water-soluble polyhydroxylated fullerene, i.e. a fullerenol, with 44 hydroxyl groups and 8 secondary bound water molecules, C₆₀(OH)₄₄·8H₂O (estimated average structure), has been synthesized in a facile one step reaction from pristine C₆₀ by hydroxylation with hydrogen peroxide in the presence of a phase-transfer catalyst, tetra-n-butylammonium hydroxide (TBAH), under organic/aqueous bilayer conditions. The fullerenol exhibited high water solubility, up to 64.9 mg/mL, under neutral (pH = 7) conditions. Dynamic light-scattering (DLS) analysis showed a narrow particle size distribution, of 1–2 nm, indicating that the fullerenol had high dispersion properties in water. The results of particle size analyses, which both focused on a single nanoregion and were conducted using a novel induced grating (IG) method and a scanning probe microscope (SPM), were consistent with the DLS results. A plausible reaction mechanism, which includes fullerene oxide intermediates detected by liquid chromatography-mass spectrometry (LC-MS), has been proposed.     

Effect of pulsed DC current on neck growth between tungsten wires and tungsten plates during the initial stage of sintering by the spark plasma sintering method

The spark plasma sintering of tungsten wires to tungsten plates was investigated to assess the effect of the current. Neck growth between wires and plates was about 1.5 larger in the presence of current than when the current was absent. The neck growth was controlled by an evaporation–condensation mechanism. The mechanism, however, does not relate to the sintering of tungsten, but to the control of a surface oxide reduction, in agreement with previous investigations.     

Study on the breaking behavior of self-bursting microcapsules

We have successfully prepared “self-bursting” microcapsule. The microcapsule retains its shape when suspended in water but breaks open quickly after the water evaporates. In this report, the breaking behavior of MC, which encapsulated insecticide (pyriproxyfen) with polyurethane via an interfacial polymerization method, was studied. In order to investigate the self-bursting phenomenon more detail, we studied the relationships between the self-burst ratio and the self-weight of the microcapsule, capillary force, and critical buckling stress. As a result, it was found that wall thickness affected the self-bursting phenomenon.