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We have found for the first time the reentrant lamellar/onion (lamellar-onion-lamellar) transition with varying temperature under constant shear rate by using simultaneous measurements of shear stress and small-angle X-ray scattering (Rheo-SAXS) for a nonionic surfactant (C(14)E(5))/water system, which exhibits the lamellar phase in a wide temperature range from 15-75 °C. The onion state exists in a closed region in the temperature-concentration diagram at a constant shear rate. Temperature dependence of the lamellar repeat distance (d) at rest has also been measured at several concentrations. It is shown that the increase of d with increasing temperature is necessary for the existence of the lower transition. We have investigated the change in the lamellar orientation in the lamellar-to-onion and onion-to-lamellar transition processes near the upper and lower transition temperatures. For all four kinds of transition processes, the following change in the lamellar orientation is observed; lamellar state (oriented to the velocity gradient direction) ↔ further enhancement of the orientation to the velocity gradient direction ↔ enhancement of the orientation to the neutral direction ↔ onion state.

It has been empirically known that cholesterol largely increases the viscosity of oleic acid. To clarify the mechanism of the effect of cholesterol on the intermolecular and the intramolecular (segmental) movements of oleic acid in the liquid state, we measured density, viscosity, IR, 1H NMR chemical shift, self-diffusion coefficient, and 13C NMR spin-lattice relaxation time for the liquid samples of oleic acid containing a small amount of cholesterol. Furthermore, the above measurements were also carried out for the samples of oleic acid containing a small amount of cholestanol, cholestane, cholesteryl oleate, ethanol, or benzene. Cholesterol, possessing one OH group and one double bond in its molecular structure, largely increased the viscosity and reduced the self-diffusion and the intramolecular movement of oleic acid. Cholestanol, possessing one OH group but not a double bond, and cholesteryl oleate, not possessing an OH group, also reduced the self-diffusion and the intramolecular movement; cholestane, not possessing an OH group, slightly reduced the self-diffusion and the intramolecular movements. In contrast with these sterols, ethanol and benzene reduced the viscosity and increased the self-diffusion and the intramolecular movements. In addition, cholesterol and ethanol, both having one OH group, promoted the upfield shift of the 1H NMR signal of the carboxyl group of oleic acid; IR difference spectra for the cholesterol/oleic acid system quite resemble those for the ethanol/oleic acid system. These results suggest that oleic acid makes a complex with cholesterol as well as with ethanol. On the basis of the formation of the complex, we have revealed the role and the functional mechanism of cholesterol to the intermolecular and the intramolecular movements of oleic acid in the liquid state.

The translational movement, the dynamical molecular conformation, and the aggregate structure in the liquid state for three kinds of cis-type unsaturated fatty acids (cis-6-, cis-9-, and cis-11-octadecenoic acids), trans-type unsaturated acid (trans-9-octadecenoic acid), and n-saturated acid (octadecanoic acid) have been studied through the measurements of density, self-diffusion coefficient, 13C NMR spin−lattice relaxation time, and X-ray diffraction. The magnitude of the self-diffusion coefficient, D, fell in sequence of cis-type unsaturated acids > trans-type acid > saturated acid below 350 K. Above 350 K the value of D for the trans-type acid rose to those for the cis-type acids. On the other hand, the density ρ for the acids also fell in the order of cis-type acids > trans-type acid > saturated acid; the order of the density is just opposite to that expected from the results of the self-diffusion coefficient and other physical properties such as melting point and heat of fusion. This discrepancy betw...

Two-dimensional (2D) near-infrared (NIR) correlation spectroscopy was used to study the temperature-induced changes in the hydrogen bonding of butan-1-(ol-d) and 2-methylpropan-2-(ol-d) in the pure liquid phase. The similarity between the 2D correlation spectra of both studied butanols and their nondeuterated analogues proves that the isotopic substitution in the hydroxyl group affects little the dynamic properties of the hydrogen bonding. This conclusion also confirms the heterospectral analysis, performed for the spectra of the deuterated samples and their nondeuterated counterparts. In the asynchronous spectra of 2-methylpropan-2-ol and its deuterated analogue, we identified new bands at 7040 and 5226 cm-1, respectively, which are probably due to an intramolecular effect. Moreover, a heterospectral asynchronous plot develops a peak at (5286, 7085), not seen in the homospectral 2D plots of butan-1-(ol-d) and butan-1-ol, giving rise to an additional resolution enhancement. This new peak reveals different...

The temperature-dependent near-infrared (NIR) spectral variations of n- and tert-butyl alcohols in the pure liquid state have been studied by generalized two-dimensional (2D) correlation analysis. ...

Morphological study of thin-film systems of pure fullerene (C[sub 60]) and some other amphiphilic compounds adsorbed on glass plates was conducted on the electron microscopic scale. Each component in benzene was placed on the aqueous subphase of distilled water (pH 5.8) according to the Langmuir technique to form its thin film; the thin film was transferred onto one side of a glass-plate surface by the subphase-lowering method. Each film-adsorbed site was replicated with a plasma-induced polymerized naphthalene film. The glass plates thus surface-treated were gradually dipped into 5% fluoric acid solution in order to obtain their respective single replica stage films for transmission electron microscopic observation. For example, the replica image of the C[sub 60] thin-film was able to show numerous necklace-like patterns forming a two-dimensional network on the electron microscopic scale. This network structure provides the possibility of applicational utilities such as a superconductive thin-film. 22 refs., 9 figs.

Flow (rheological) properties and dynamic viscoelasticity of concentrated solutions of a hybrid surfactant containing a fluorocarbon chain and hydrocarbon chain within a single molecule were analyzed. The results indicated that the viscosity of the hybrid surfactant solution is not proportional to the increase in its concentration, and it showed an anomalously large value around a 10 wt % solution. It was also indicated that the surfactant solution in this range of concentration behaves like a viscoelastic substance with a characteristic of rubber like elasticity.

The thermal viscosity behavior or temperature-dependent viscosity of an aqueous solution of sodium 1-oxo-1-[4-(tridecafluorohexyl)phenyl]-2-hexanesulfonate (FC6-HC4), a fluoro-hybrid type surfactan...