Shigeyoshi Miyagishi

Influence of external environment on microviscosity in micelles

Abstract N,N,N′,N′ -Tetramethyldiaminodiphenylketoimine hydrochloride was used as a probe to determine the microviscosity in micelles of sodium dodecyl sulfate (SDS). The fluorescence intensity of the probe increased with an increasing concentration of SDS up to its critical micelle concentration, and then it became nearly constant. The microviscosity in the SDS micelles was estimated to be 5 cP. Addition of urea or NaCl, a change from H 2 O to D 2 O, or a variation in temperature produced different effects on the probe in the micelle and bulk phase, respectively. Addition of urea and substitution of D 2 O for H 2 O increased the microviscosity. The microviscosity in the micelles decreased as the temperature rose. The increment in the fluorescence intensity in the micelle solution was small up to 0.3 M NaCl and then the intensity increased steeply with addition of more NaCl. This abrupt change corresponded to a sphere-rod transition in the micelle form.

Influence of chirality on micelle formation of sodium N-acylalanates and sodium N-lauroylvalinates

Abstract The critical micelle concentrations (cmc) of the optical isomers of sodium N -acylalanates and sodium N -lauroylvalinates were measured. The optically active isomers had the smallest cmcs in all NaCl solutions and at all temperatures. The degrees of counterion dissociation from the micelle (α) were determined and found to be identical for the optically active isomers and the racemic mixtures. The effective coefficients of electrostatic interaction ( K g ) and the free energy of transfer per methylene group from water to micelle (ω), respectively, are identical in both solutions. The thermodynamic parameters of micellization for the optically active surfactants were smaller than those for the racemic ones. It was concluded that the difference between the cmc values of the racemic and the optically active isomers results from the difference of the conformation of amino acid part in the surfactant molecule on the surface of the micelles.

Critical micelle concentration in mixtures of N-acyl amino acid surfactants

Abstract The critical micelle concentrations (CMC) were determined in the mixed solutions of N-lauroyl amino acid sodium salts. The results suggested that steric hindrance of its amino acid residue was not always significant on formation of the mixed micelle. In addition, a model was proposed to predict the CMC in the mixed system without an adjustable parameter. It was found that the model was applicable to the systems that deviated significantly from ideal mixing.

Fluorine nuclear magnetic resonance of fluorocarbon and hydrocarbon surfactant mixtures

Etudes des interactions dans les micelles mixtes fondees sur le deplacement chimique de 19 F du groupe CF 3 dans les systemes mixtes de tensioactifs fluorocarbure et hydrocarbure. Cas des perfluorooctanesulfonate de Li ou de Na et des decyl- ou -laurylsulfate de sodium

NMR study about solubilization of phenyl alkyl alcohol in sodium dodecyl sulfate micelle and in Brij 35 micelle

Abstract The NMR spectra of sodium dodecyl sulfate (SDS) solutions and of Brij 35 solutions were examined in the presence of benzyl alcohol, 2-phenylethanol, 3-phenylpropanol, or 2-phenylethylamine. The signal of the methylene chain in SDS split into an up-field signal and a down-field signal with broadening. The addition of 3-phenylpropanol produced a down-field shift of the methyl signal of SDS, and the addition of 2-phenylethylamine produced not only a down-field shift of the methyl signal but also a down-field shift of the inner methylenes in SDS. The other signals were up-field shifted by the addition of the phenyl derivatives. The signal of the methylene chain was resolved into three peaks (I, II, III) by a computer simulation method. Peak I was assigned to the methylene groups close in the β-methylene of the surfactant. It was concluded that the phenyl alcohol was solubilized with its polar head near the micelle surface and with the phenyl group in the region of the middle methylenes of the micelle. In the Brij 35 solutions, the solubilization site of the alcohol varied gradually from the polyoxyethylene mantle of the micelle to its inner hydrocarbon region with increasing size of the alcohol.

Hydrophobicity and surface activities of sodium salts of N-dodecanoyl amino acids

Abstract Surface tensions of N-dodecanoyl amino acids were measured in 100 mM NaOH solution at 45.0°C. The dependence of the surface tension γ on the surfactant concentration (CA−) was expressed by the equation γ = γ0 - RTΓmln(1 + KCA). The saturated adsorbed amount of surfactant at the air-water interface Γm varied somewhat with different amino acid side chains. The hydrophobicity of an amino acid was defined by using the critical micelle concentration (CMC(X)) of its N-dodecanoyl derivative as Δg = ln CMC(X) − ln CMC(glycinate). A progressive increase in hydrophobicity produced an increase in K and in the surface pressure at CMC (πCMC). A linear relationship existed between Δg and efficiency in surface tension reduction, pC20, i.e., the logarithm of reciprocal of the concentration when γ0 − γ is 20 mN/m. It was found that the amino acid side chains in the surfactants did not have a hydrophobic interaction with the dodecanoyl grup.

Effect of amino acid surfactants on phase transition of poly(N-isopropylacrylamide) gel

The volume phase transition behavior of a poly(N-isopropylacrylamide) gel (NIPA gel) in solutions of N-acyl amino acid surfactants were studied as a function of surfactant concentration. The addition of a surfactant beyond the critical micelle concentration (cmc) produced elevation in the transition temperature of the NIPA gel and its swelling. The changes in the volume phase transition temperature and in the swelling of the NIPA gel became more significant with the decreasing size of the amino acid side chain. This result could almost be explained only by the binding amount of surfactant onto the NIPA gel regardless of molecular structure of the amino acid. The binding amount increased in the order of sodium N-lauroyl-glycinate>-alaninate>-valinate>-leucinate>or=-phenylalaninate. For an N-acyl amino acid surfactant to bind onto the NIPA gel, to increase the transition temperature, and to facilitate swelling of the gel, the steric hindrance of the amino acid side chain was more effective than its hydrophobicity.

Association of alkylpyridinium halides in nonaqueous solvents

SummaryAssociation numbers and absorption spectra of alkylpyridinium halides were measured in nonaqueous solvents. The association behaviors depended on alkyl chain length of the surfactant, its counterion, the concentration, temperature, and the polarity of solvent. Alkylpyridinium bromides were found to associate even below the critical solubility temperature (CST).ZusammenfassungEs wurden Assoziationszahlen und Absorptionspektra von Alkylpyridiniumhaliden in den nichtwasserigen Lösungsmitteln untersucht. Die Assoziationstendenz wird von dem Alkylrest des Tensides, dem Gegenion, dem Lösungsmittel und der Temperatur beeinflußt. Alkylpyridiniumbromide assoziieren sogar unter der kritischen Lösungstemperatur.

Synthesis of Nano‐Sized TiO2 Colloidal Sol and Its Optical Properties

Nano‐sized TiO2 sol was prepared through a wet synthesis process. The synthesis procedure involved hydrolysis of TiCl4, acid treatment, and a SiO2 surface‐modifying process. Before surface modification, the TiO2 suspension was treated with acid to remove Na ions, soluble TiO2, and other impurities. The acid treatment of a TiO2 suspension at a higher temperature was proved to be useful for effective SiO2 modification. The colloidal sol provided high transparency in visible light as well as excellent UV‐shielding properties. Surface modification of TiO2 particles with SiO2 greatly improved both the dispersing stability in neutral pH and the photostability of TiO2 colloidal sol.

Solubilization of octafluoronaphthalene by mixed micelles of fluorocarbon and hydrocarbon surfactants in aqueous solutions

Solubilization of octafluoronaphthalene (OFN) by fluorocarbon and hydrocarbon surfactants in aqueous solutions has been examined to investigate the effects of mixing surfactants and added salt. Diethylammonium perfluoronanoate (DEAPFN) micelles have the most solubilization power toward OFN. The difference in micellar solubilization power will be caused by the hydrophobicity of ionic groups and micellar size. Large positive synergistic effects on solubilization behavior were observed in the DEAPFN-diethylammonium tetradecyl sulfate mixed micellar systems. Solubilization of OFN depended on the concentrations of added salt and the aggregation number, that is, the micellar size.