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Title: Quaternary water in oil microemulsions. 1. Effect of alcohol chain length and concentration on droplet size and exchange of material between droplets

Abstract

Water solubility, electrical conductivity, and time-resolved fluorescence quenching measurements have been performed in water/chlorobenzene/cationic surfactants/1-alcohol water-in-oil (w/o) microemulsions in order to investigate the effect of alcohol chain length and concentration on various properties of these systems: surfactant aggregation number, N, per aggregate; radius, R{sub w}, of the droplet water core; intensity of attractive interdroplet interactions; onset of percolation of electrical conductivity; and rate constant, k{sub e}, for the exchange of material between droplets through collisions with temporary merging. The variations of these properties with the molar concentration ratio {omega} = (water)/(surfactant) for alcohols of increasing chain length are strikingly similar to those found when investigating the effect of surfactant chain length. In particular, N and R{sub w} and the intensity of attractive interactions decrease when the alcohol chain length increases as predicted by current theory of the stability of w/o microemulsions. For a series of microemulsions based on alkyltrimethylammonium bromide surfactants, the water solubility results indicate that the stability of the microemulsions containing short chain alcohols (propanol, butanol) is determined by the attractive interdroplet interactions. The results give support to the mechanism postulated for electrical conductivity above the percolation threshold, namely, motion of counterions through transient water tubes formed inmore » the droplet clusters present in the systems. Finally, it is shown that simple electrical conductivity and water solubility measurements can yield of quantitative information about the investigated microemulsions.« less

Authors:
; ;  [1]
  1. (Inst. Charles Sadron (France))
Publication Date:
OSTI Identifier:
7017457
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry; (United States); Journal Volume: 95:23
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 02 PETROLEUM; CHLORINATED AROMATIC HYDROCARBONS; FLUORESCENCE SPECTROSCOPY; PHYSICAL PROPERTIES; OILS; SURFACTANTS; WATER; CATIONS; DROPLETS; ELECTRIC CONDUCTIVITY; EXPERIMENTAL DATA; MASS TRANSFER; MICROEMULSIONS; PARTICLE SIZE; QUANTITY RATIO; QUENCHING; SOLUBILITY; TIME RESOLUTION; AROMATICS; CHARGED PARTICLES; COLLOIDS; DATA; DISPERSIONS; ELECTRICAL PROPERTIES; EMISSION SPECTROSCOPY; EMULSIONS; HALOGENATED AROMATIC HYDROCARBONS; HYDROGEN COMPOUNDS; INFORMATION; IONS; NUMERICAL DATA; ORGANIC CHLORINE COMPOUNDS; ORGANIC COMPOUNDS; ORGANIC HALOGEN COMPOUNDS; OTHER ORGANIC COMPOUNDS; OXYGEN COMPOUNDS; PARTICLES; RESOLUTION; SIZE; SPECTROSCOPY; TIMING PROPERTIES; 400201* - Chemical & Physicochemical Properties; 020300 - Petroleum- Drilling & Production

Citation Formats

Lang, J., Lalem, N., and Zana, R. Quaternary water in oil microemulsions. 1. Effect of alcohol chain length and concentration on droplet size and exchange of material between droplets. United States: N. p., 1991. Web. doi:10.1021/j100176a090.
Lang, J., Lalem, N., & Zana, R. Quaternary water in oil microemulsions. 1. Effect of alcohol chain length and concentration on droplet size and exchange of material between droplets. United States. doi:10.1021/j100176a090.
Lang, J., Lalem, N., and Zana, R. 1991. "Quaternary water in oil microemulsions. 1. Effect of alcohol chain length and concentration on droplet size and exchange of material between droplets". United States. doi:10.1021/j100176a090.
@article{osti_7017457,
title = {Quaternary water in oil microemulsions. 1. Effect of alcohol chain length and concentration on droplet size and exchange of material between droplets},
author = {Lang, J. and Lalem, N. and Zana, R.},
abstractNote = {Water solubility, electrical conductivity, and time-resolved fluorescence quenching measurements have been performed in water/chlorobenzene/cationic surfactants/1-alcohol water-in-oil (w/o) microemulsions in order to investigate the effect of alcohol chain length and concentration on various properties of these systems: surfactant aggregation number, N, per aggregate; radius, R{sub w}, of the droplet water core; intensity of attractive interdroplet interactions; onset of percolation of electrical conductivity; and rate constant, k{sub e}, for the exchange of material between droplets through collisions with temporary merging. The variations of these properties with the molar concentration ratio {omega} = (water)/(surfactant) for alcohols of increasing chain length are strikingly similar to those found when investigating the effect of surfactant chain length. In particular, N and R{sub w} and the intensity of attractive interactions decrease when the alcohol chain length increases as predicted by current theory of the stability of w/o microemulsions. For a series of microemulsions based on alkyltrimethylammonium bromide surfactants, the water solubility results indicate that the stability of the microemulsions containing short chain alcohols (propanol, butanol) is determined by the attractive interdroplet interactions. The results give support to the mechanism postulated for electrical conductivity above the percolation threshold, namely, motion of counterions through transient water tubes formed in the droplet clusters present in the systems. Finally, it is shown that simple electrical conductivity and water solubility measurements can yield of quantitative information about the investigated microemulsions.},
doi = {10.1021/j100176a090},
journal = {Journal of Physical Chemistry; (United States)},
number = ,
volume = 95:23,
place = {United States},
year = 1991,
month =
}
  • Ternary water in oil microemulsions made of cationic surfactants, water, and aromatic solvents have been investigated by means of time-resolved fluorescence quenching, quasi-elastic light scattering, and electrical conductivity in order to determine the surfactant aggregation number N per water droplet, the rate constant k{sub e} for the exchange of material between droplets through collisions with temporary merging, the droplet diffusion coefficient D, and the coefficient of interaction between droplets {alpha} and to study the occurrence of electrical percolation as a function of the surfactant chain length, head-group size, and water content of system (expressed as the molar concentration ratio {omega}more » = (water)/(surfactant)). Most measurements were performed with chlorobenzene as solvent. In one instance, chlorobenzene was substituted by benzene in order to investigate the effect of the nature of the solvent. For a given surfactant, N and k{sub e} increased with {omega} and upon substituting chlorobenzene by benzene. Also, at a given {omega}, N and k{sub e} increased when the surfactant chain length was decreased. The increases of k{sub e} were always extremely large. The droplet hydrodynamic radii from quasi-elastic light scattering were found to agree with the droplet sizes calculated with the N values from fluorescence quenching. The droplet interaction coefficient {alpha} became more negative as the surfactant chain length decreased, indicating increasingly attractive interdroplet interactions. Finally, electrical percolation was found to occur in all systems where interdroplet interactions were sufficiently attractive. The percolation threshold {omega}-values increased with surfactant chain length.« less
  • The rate constant k{sub e} associated with the exchange of material upon collisions between droplets in ternary water in oil microemulsions stabilized by ionic surfactants has been determined by a time-resolved fluorescence method. The electrical conductivity of the same systems has been investigated. It appears that percolative conduction occurs only in systems where k{sub e} is larger than (1-2) {times} 10{sup 9} M{sup {minus}1} s{sup {minus}1}. This result supports the hypothesis that above percolation threshold the conductivity is mainly due to the motion of counterions through water channels or fusion between droplets in droplet clusters.
  • Ternary water-in-oil microemulsions using alkylbenzyldimethylammonium chloride (alkyl = dodecyl (N12), tetradecyl (N14), and hexadecyl (N16)) surfactants and benzene or chlorobenzene as oils have been investigated by means of electrical conductivity and NMR self-diffusion. The variations of the water self-diffusion coefficient with the (water)/(surfactant) molar concentration ratio {omega} and with the volume fraction of benzene in the oil mixture in water/(benzene + chlorobenzene)/N16 microemulsions are well correlated with the changes of electrical conductivity, as expected from a model of microemulsions where the water cores of the droplets become increasingly connected above the percolation threshold. These connections, however, have a strongly dynamicmore » character. This model permits the authors to explain the widely differing magnitudes of the changes of electrical conductivity, water self-diffusion coefficient, and rate of exchange reactants between droplets upon increasing {omega}. The self-diffusion coefficient of the oil has been found to be about half that of the bulk oil, as in studies reported by others.« less
  • The influence of counterion on micelle structure is examined for a series of trimethylammonium halide surfactants C{sub n}TAX = C{sub n}H{sub 2n+1} N(CH{sub 3}){sub 3}{sup +}X{sup {minus}}(X = NO{sub 3}, Br, CH{sub 3}SO{sub 4}, Cl, and OH) by small-angle neutron scattering. The variation of micelle structure as a function of chain length (n - 12, 14, and 16) and surfactant concentration (0.05, 0.1, and 0.2 mol dm{sup {minus}3}) is also studied. It was found that the aggregation number, N, increases in the order of NO{sub 3} > Br > CH{sub 3}SO{sub 4} > Cl >> OH. This order is roughlymore » correlated to the fractional micellar charge, {beta}, which follows the order OH > Cl > CH{sub 3}SO{sub 4} {approximately} Br {approximately}NO{sub 3}. Fractional charge changes very little and in an irregular fashion when n and/or surfactant concentration are increased, but the aggregation number increases with respect to both. 13 refs., 2 figs., 3 tabs.« less
  • Platinum nanoparticles size range from 1 to 8 nm deposited on mesoporous silica MCF-17 catalyzed alcohol oxidations were studied in the gas and liquid phases. Among methanol, ethanol, 2- propanol and 2-butanol reactions, the turnover frequency increased with Pt nanoparticle size for all the alcohols utilized. The activation energies for the oxidations were almost same among all alcohol species, but higher in the gas phase than those in the liquid phase. Water coadsorption poisoned the reaction in the gas phase, while it increased the reaction turnover rates in the liquid phase. Sum frequency generation (SFG) vibrational spectroscopy studies and DFTmore » calculations revealed that the alcohol molecules pack horizontally on the metal surface in low concentrations and stand up in high concentrations, which affect the dissociation of β-hydrogen of the alcohols as the critical step in alcohol oxidations.« less