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To reveal the interaction between cationic fluorocarbon and cationic hydrocarbon surfactants, the mixed critical micelle concentration (CMC) of diethanolheptadecafluoro-2-undecanolmethylammonium chloride (DEFUMAC) and dodecyltrimethylammonium chloride (DTAC) in aqueous solution was determined using electrical conductivity measurements. An interaction parameter, β, of 1 was obtained by applying a regular solution theory (RST) to the mixed CMC. Further, partition coefficients of alcohols and pyrene-3-carboxaldehyde between the micelles and the aqueous phase were measured. All these data were interpretable using RST with β = 1, indicating a rather small repulsive interaction between DEFUMAC and DTAC compared with anionic fluorocarbon and hydrocarbon surfactant mixtures. This is due to the large different CMC values of the two surfactants.

Adsorption of Aerosol OT on alumina particles, preheated at 25°C or 300°C, from hexane and cyclohexanone was studied using two types of nitroxide probes. From the electron spin resonance spectra, the interaction between alumina surfaces having different amounts of water and Aerosol OT was discussed.

The interaction of poly(sodium 4-styrenesulfonate) (PSS) with the cationic surfactants hexadecyltrimethylammonium chloride (CTAC) and diethanol heptadecafluoro-2-undecanol methylammonium chloride (DEFUMAC), has been studied by surface tension, viscosity, fluorescence, and solubilization measurements. The anionic polymer can form complexes with CTAC or DEFUMAC. The complex ratio of the surfactant to PSS is lower for the PSS-DEFUMAC system than for PSS-CTAC, and complex formation of PSS-DEFUMAC is much more favorable than that of PSS-CTAC. These complexes provide a hydrophobic environment, where the micropolarity of the PSS-DEFUMAC complex sensed by pyrene-1-carboxaldehyde is higher than that of PSS-CTAC, and the solubilization capacity of Yellow OB by the PSS-DEFUMAC complex is lower than that of PSS-CTAC.

Adsorption of dioctadecyldimethylammonium chloride (DODAC) on silica from its vesicle in aqueous solution has been studied. The adsorption isotherm indicates that the interaction between DODAC and silica is strong because of the electrostatic attraction force and that a patch-like bilayer is probably formed. Fluorescence and ESR probe measurements show that the micropolarity of the DODAC adsorbed layer on silica is lower, but its microviscosity is higher, compared to those of the DODAC vesicle in aqueous solution. Further, Yellow OB, a water-insoluble dye, is incorporated in the DODAC adsorbed layer indicating its hydrophobic nature; the incorporated Yellow OB is barely removed by washing with deionized water.

The solubilization of hydrocarbon and fluorocarbon alcohols in single and mixed aqueous solutions containing fluorocarbon surfactant has been studied. Surfactants used are lithium dodecyl sulfate (LiDS), lithium perfluorooctane sulfonate (LiFOS), lithium perfluorooctanoate (LiPFO), and hexaethyleneglycol dodecyl ether (6ED). In single surfactant systems, the partition coefficients of the alcohols between anionic micelles and water are greater for the surfactants which have the same kind of alkyl chain as the alcohols than for the surfactants having a different kind of alkyl chain to the alcohols. The standard free energies calculated from the partition coefficients indicate that the transfer of the alcohols occurs more favorably to the micelles consisting of the same kind of alkyl chain as the alcohols than of the different kind of alkyl chain. Also, the mixed surfactant systems LiDS-LiFOS, LiFOS-LiPFO and 6ED-LiFOS have been characterized by the regular solution parameter β and the alcohol partition coefficient. In the LiDS-LiFOS system with a positive β value, the partition coefficients of both hydrocarbon and fluorocarbon alcohols are greater than in single surfactant systems. In the LiFOS-LiPFO system exhibiting almost ideal mixing, the partition coefficients of both hydrocarbon and fluorocarbon alcohols change ideally, whereas the partition coefficients of the fluorocarbon alcohols are greater than those of the hydrocarbon alcohols. By contrast, in the 6ED-LiFOS system with negative β values, the partition coefficients of both alcohols are lower than in single surfactant systems.

The cationic surfactant layer adsorbed on silica has been characterized by measuring the adsorbed amount of surfactant, electron spin resonance and fluorescence spectra. The adsorption of dodecylpyridinium chloride (DPCI) and cetylpyridinium chloride (CPCl) on negatively charged silica leads to formation of a bilayer by the interaction between hydrophobic chains of the first and second surfactant layers. The bilayers of these surfactants exhibit a lower micropolarity and a greater microviscosity than those in their micelles. Further, adsolubilization experiments indicate that hexanol is not solubilized in the bilayers of DPCl but is in the bilayer of CPCl. It is found that incorporation of hexanol renders the micropolarity of the DPCl bilayer slightly higher, whereas it renders the microviscosity of the CPCl bilayer much higher, compared with those without hexanol.

Precious metal particles (Au, Pt, Pd, Rh) were prepared using chitosan as a protective agent. The particle sizes decreased with increasing amounts of chitosan, while the dispersion stability against electrolyte increased. Similarly, stable bimetallic particles of AuPd and AuRh were obtained and their particle sizes were almost independent of feed composition. Furthermore, these bimetallic particles exhibited characteristic properties for the decomposition of hydrogen peroxide and hydrogenation of methylvinylketone.

The surfactant layer formed on alumina by addition of lithium perfluorooctane sulfonate (LiFOS) was characterized in the water—dioxane system. Alumina exhibited a dispersion—flocculation—redispersion process by the addition of LiFOS as a result of the formation of a bilayer at low, but not high dioxane levels. The behavior was well correlated with zeta potential measurements and the amount of adsorbed LiFOS. Furthermore, fluorescence and electron spin resonance measurements indicate that the micropolarity and microviscosity of a LiFOS adsorbed layer on alumina are significantly altered on increasing the content of dioxane in solution.

The effect of lithium perfluorooctane sulfonate (LiFOS) on a dispersion of alumina in water—alcohol mixtures was studied by measuring the zeta potential, the turbidity of alumina, and the amount of LiFOS adsorbed. With a low alcohol content, flocculation, then redispersion of alumina by adsorption of LiFOS was observed, whereas the dispersion of alumina in a high alcohol content gradually decreased with adsorption of LiFOS. This dispersion behavior of alumina is also affected with the length of carbon chain of the alcohol.

Gold particles were prepared by the reduction of extracted chlorauric acid with hydrazine/ formaldehyde/benzaldehyde. The extractants used were as follows: distearyldimethylammonium chloride (DDAC), trioctylmethylammonium chloride (TMAC) and trioctylphosphine oxide (TOPO). The extraction ratio of Au(III) increased in chloroform and cyclohexane with an increase in the concentration of extractants. The particle size of gold obtained by reduction of the extracts decreased with an increase in extraction ratio. In the TOPO-cyclohexane-hydrazine system in particular, very stable gold particles with an average diameter of 6.8 nm were obtained in the presence of excess of TOPO.

Properties of mixed bilayers of anionic hydrocarbon-anionic fluorocarbon or non—ionic hydrocarbon surfactants, and of anionic fluorocarbon—anionic hydrocarbon or non-ionic hydrocarbon surfactants on monodispersed ferric hydro sols have been investigated by measuring the amount of surfactant adsorbed, particle size and zeta potential. After the positive charged sols are flocculated upon addition of anionic hydrocarbon or anionic fluorocarbon surfactant as a first additive, a second additive different from the first one is added to it. The data on the amount of surfactant adsorbed indicate that the mixed bilayers of anionic hydrocarbon—non-ionic hydrocarbon surfactants and of anionic fluorocarbon—non-ionic hydrocarbon surfactants are formed more preferentially than those of anionic hydrocarbon—anionic fluorocarbon surfactants. These behaviors are correlated with those for particle size and zeta potential of the sols.

The interaction between hydrocarbon and fluorocarbon surfactants has been studied through flocculation-redispersion of monodispersed ferric hydro sols. When a very low concentration of anionic hydrocarbon or anionic fluorocarbon surfactant is added to positively charged sols, the sols flocculate. Whether the flocculated sols redisperse upon further addition of fluorocarbon or hydrocarbon surfactant has been investigated by measuring zeta potential, turbidity and particle size. From the results of redispersion of the sols, it is found that the hydrophobic interaction between anionic fluorocarbon and anionic hydrocarbon surfactants is less significant than that between anionic-nonionic fluorocarbon and hydrocarbon surfactants.

An emulsion polymerization of styrene in the presence of a zwitterionic emulsifier,N,N-dimethyl-n-laurylbetaine (LNB), was carried out at pH 7.0. The stability of mixed dispersions composed of latex particles prepared with the emulsifier (LNB) and titanium dioxide particles was studied as a function of pH. The zeta potential of the synthesized latex particles was significantly dependent on the pH and showed the existence of an isoelectric point. In the pH range of 3.0–8.3, where the latices are positively charged while titanium dioxide pigment particles are negatively charged, the mixed suspensions of the latices and titanium dioxide particles were dispersed but exhibited heterocoagulation with increasing particle number of the latices. Furthermore, titanium dioxide particles were restabilized with further addition of the latices. The mechanisms of these processes are discussed. A similar experiment was conducted with silica particles.

Adsorption of 7,7,8,8-tetracyanoquinonedimethane (TCNQ) onto alumina and titania from three basic and two acidic solvents was carried out. The amount of adsorption of TCNQ on the metal oxides was fairly well correlated with the basicity or acidity of the solvent which is estimated by their calculated heat of interaction with TCNQ or with the electron-donor sites of the metal oxide. Furthermore, the concentration of TCNQ radicals formed as a result of electron transfer from the electron-donor sites to TCNQ for the two metal oxides decreased considerably with increasing basicity of the solvent, but changed a little with increasing acidity of the solvent, particularly for titania.

The color of an aqueous tri-iodide ion (I 3 − ) solution fades in the presence of anionic surfactants, such as sodium dodecyl sulfate (SDS), sodium di-2-ethylhexyl sulfosuccinate (Aerosol OT) and sodium 4-sulfobutyl laurate (11C-4), when the added concentration of anionic surfactant is above the c.m.c. These results can be explained by the acceleration of hydrolysis of I 3 − in the presence of negatively charged micelles. The hydrogen ions are sequestered by anionic micelles from the aqueous solution, resulting in a change in the bulk solution property due to hydroxyl ions remaining after the fixation of protons at the micelles, and leading to an increase in the rate of hydrolysis of I 3 − . Further, the fading of I 3 − in aqueous solution depends on the type of surfactant and the concentration of sodium chloride. Above the surfactant c.m.c. the fading of the color of the I 3 − solution becomes slower with increasing concentration of sodium chloride, eventually reaching zero, except in the case of SDS. This salt effect can be explained by the exchange between hydrogen and sodium ion at the surface of the anionic micelle. The magnitude of hydrolysis of I 3 − in the various anionic surfactants in the presence of sodium chloride occurs in the following order: AOT>11C-4>SDS.