Kenji Ohki

Some micellar properties of straight-chain sodium alkylbenzene sulfonates

SummaryMeasurements of viscosities, densities, sedimentation and diffusion coefficients have been made of the micellar solutions of a series of straight-chain sodium alkylbenzene sulfonates, CnH2n+1C6H4SO3Na withn from 10 to 15. For the lower members of the surfactants, withn=10 and 12, the effects of the position of phenyl group on the micellar proporties were examined. It is estimated from the above hydrodynamic data that the micelles of the lower members are small, spherical and highly hydrated while those of the higher members are comparatively large and asymmetric. The micellar properties of the lower members are dependent on their phenyl position. In addition, the electrophoretic mobilities of the micelles were measured to obtain theζ-potential of the micelles and to learn their electrochemical behaviors.ZusammenfassungAn Lösungen der geradkettigen Natrium-Alkylbenzolsulfonaten, CnH2n+1C6H4SO3Na mitn von 10 bis 15, wurden oberhalb der kritischen Mizellkonzentration die Viskosität, die Dichte sowie die Sedimentations- und Diffusionskoeffizienten gemessen. Bei den Verbindungen mit n=10 und 12 wurde untersucht, welchen Einfluß die Stellung der Phenylgruppe auf die Eigenschaften der Mizellen hat. Aus den hydrodynamischen Messungen wurde gefolgert, daß die Mizellen der kurzkettigen Verbindungen klein, kugelförmig und stark hydratisiert sind, während die der längerkettigen ziemlich groß und asymmetrisch sind. Die Eigenschaften der Mizellen der kurzkettigen Verbindungen sind dabei abhängig von der Stellung der Phenylgruppen. Weiterhin wurde die elektrophoretische Beweglichkeit der Mizellen gemessen, um ihreζ-Potentiale zu erhalten.

Surface chemical properties in aqueous solutions of sodium alkylbenzene sulfonates

Abstract Surface tension measurements have been made on aqueous solutions of sodium alkylbenzene sulfonates in the presence of sodium chloride. The total free energy change in adsorption, ΔGtotal, obtained from the above data by assuming two different types of adsorption models, has been discussed in the light of the treatment recently developed for adsorbed ionic monolayers. The adsorbed molecules at an air/water interface would seem to be immobile. With an immobile model, the free energy change in adsorption, ΔG0, exclusive of electrical energy and cohesional energy of the monolayer, involved in transferring a molecule from the bulk to the surface has been estimated in the presence of sodium chloride of a constant concentration. The value of ΔG0 does not depend on the fractional coverage, but increases approximately 1.3 kcal/mole in going from decyl- to dodecylbenzene sulfonate. This shows that Traubes rule holds good even for surfactants having a hydrocarbon chain to which a benzene ring is attached. The effect of the concentration of the electrolyte on the free energy of adsorption was obtained when the concentration of sodium chloride was changed up to 0.10 M. Addition of the excess electrolyte raises ΔGtotal whereas it lowers ΔG0.

The effects of small ions and long-chain alkyl ions on the potentiometric behavior of micelles of dimethyldodecylamine oxide

Abstract The effects of small ions (z+z− electrolytes) and long-chain alkyl ions (ionic surfactants) on the surface potential ψ0 of the micelle of a cationic-nonionic surfactant, dimethyldodecylamine oxide, have been studied by potentiometric titrations of its micellar solutions. The effect of small ions on ψ0 is in accord with the effect predicted from the Gotuy-Chapman equation for spherical particles. Small counter-ions, especially their valences, have considerable influence on ψ0 whereas co-ions have no remarkable influence. The effect of long-chain alkyl ions on ψ0 is directly related to the charge properties of the added surfactant, probably owing to the formation of mixed micelles with the amine oxide surfactant.

The effect of temperature on the surface potentials of surfactant micelles

SummaryThe effect of temperature on the surface potentials of the micelles of nonionic-cationic surfactants, dimethyldodecylamine oxide and dihydroxyethyldodecylamine oxide, have been determined by their potentiometric titrations at temperatures of 5°–35 °C. The relations between charge density at the micellar surface and temperature have been obtained on the basis ofGouy-Chapmans model for a charged plane, from which the structure of the micelles was discussed. Further, the heats of ionization of the micelles have been estimated from these charge density vs. temperature relations.ZusammenfassungEs wurde der Einfluß der Temperatur auf das Oberflächenpotential der Mizellen von nichtionisch-kationischen grenzflächenaktiven Substanzen (Dimethyldodecylaminoxyd und Dihydroxyäthyldodecylaminoxyd) durch potentiometrische Titrationen über den Temperaturbereich von 5–35 °C untersucht. Die Beziehungen zwischen der Ladungsdichte an der Oberfläche der Mizellen und der Temperatur wurden auf der Basis desGouy-Chapmanschen Modells für eine geladene plane Fläche abgeleitet und zur Ermittlung der Struktur der Mizellen herangezogen. Aus der Beziehung zwischen Oberflächenladungsdichte und Temperatur wurden die Ionisierungswärmen der Mizellen berechnet.

Thermodynamic studies of the micellization and micellar solubilization of a nonionic-cationic surfactant

SummaryThe effect of the charge of a nonionic-cationic surfactant, dimethyldodecylamine oxide, on micellization and micellar solubilization has been studied thermodynamically by means of solubilization measurements for Yellow OB. The enthalpy and entropy changes during micellization were positive for the nonionic species and negative for the ionic species. Similar sign reversal in the enthalpy of micellar solubilization was also obtained in the dimethyldodecylamine oxide-Yellow OB system. The results have been discussed in the light of current concepts of micelle formation.ZusammenfassungEs wurde der Einfluß der Ladung einer grenzflächenaktiven Verbindung (Dimethyldodecylaminoxyd), die je nach demph-Wert im System entweder als Kation oder als ungeladenes Molekül vorliegen kann, auf die Bildung von Mizellen und auf Mizellarsolubilisation im System Dimethyldodecylaminoxyd-Yellow OB-Wasser untersucht. Die Enthalpie- und Entropieänderungen der Mizellbildung waren mit der ungeladenen Form positiv, bei der geladenen negativ.Weiterhin wurde die Mizellarsolubilisation von Yellow OB in Abhängigkeit von der Konzentration der grenzflächenaktiven Substanzen bestimmt. Die hieraus ermittelten Lösungsenthalpien zeigen ebenfalls eine Änderung des Vorzeichens mit steigendemph-Wert.

A New Amphoteric Surfactant having Ether-Bonds in the Molecule

A new amphoteric surfactant, sodium N-dodecyl N, N-bisethoxyacetate (NaDEA), has been synthesized by the reaction of N-dodecyl N, N-bishydroxyethylamine with sodium monochloroacetate in the presence of sodium hydroxide. NaDEA has high solubility in water and is soluble even at its isoelectric point, probably owing to the ether-bonds in the molecule. The electrical state of NaDEA greatly depends on the pH of the solution, which governs its physicochemical properties. The electrostatic potential of the micelle calculated from the pH titration data is negative above pH 3. The solubilizing power for Yellow OB changes with the pH of the solution and it is greater in the acid region than in the alkaline region. The critical micelle concentration estimated from the solubilization-concentration curve also changes with pH. Some properties, such as solubilizing power, foaming power and adsorption, of the mixed solutions of NaDEA with sodium dodecyl polyoxyethylene sulfate or sodium dodecylbenzene sulfonate have been examined. Interactions between these surfactants have been observed in the mixed solutions.