Raymond L. Venable

The effects of divalent metal ions on the micellar properties of sodium dodecyl sulfate

Abstract Critical micelle concentrations and micellar molecular weights have been determined for sodium dodecyl sulfate in the presence of nitrates of copper, lead, zinc, and magnesium and critical micelle concentrations have been determined with sodium nitrate and silver nitrate as the added electrolytes. The thickness of the ionic atmosphere at the critical micelle concentration has been found to be 34.1 A with no electrolyte present and 33.6 A with 9.66 × 10−6M sodium or silver nitrate and was found to increase upon addition of the 2:1 electrolytes. This is explained in terms of molecular and ionic interactions. Micellar molecular weights were found to be 14,200 in the absence of extraneous electrolyte, 14,700 in the presence of 4.86 × 10−4M copper II, zinc, and magnesium, 18,000 with 4.83 × 10−4M lead, and 25,000 with 9.66 × 10−4M zinc. Part of the change in micellar molecular weight is attributed to replacement of sodium ions with heavier ions, especially in the case of lead.

Conductivity study of the microemulsion system sodium dodecyl sulfate-hexylamine-heptane-water

Abstract Conductivity measurements on this system are interpreted in terms of the percolation and effective medium theories. From this interpretation, the ratio of hexylamine to sodium dodecyl sulfate in the microemulsion droplet surfaces can be deduced. Following that determination it is possible to obtain approximate values for the radius of the water pools and the number and surface area of droplets per unit volume of the microemulsion system.

Microemulsions with high water solubilizing capacity at high hydrocarbon levels and very low surfactant concentrations

Abstract Phase diagrams have been determined showing the extent of the inverse micellar or microemulsion region for systems consisting of water-surfactant-cosurfactant or water-surfactant-hydrocarbon cosurfactant mixture with three surfactants and four cosurfactants. The surfactants are sodium dodecyl sulfate, sodium laurate, and tetradecyltrimethylammonium bromide while the cosurfactants are pentanol, hexanol, pentylamine, and hexylamine. Hexylamine is found to be a very effective cosurfactant giving rise to very good water solubilizing capacity at extremely low surfactant concentrations and very low cosurfactant levels at rather high initial hydrocarbon levels.

A MICROEMULSION COSURFACTANT WITH EXCELLENT WATER SOLUBILIZATION AT HIGH OIL CONTENT

ABSTRACT Medium chain length alkyl amines were found to be more effective cosurfactants for microemulsion formation than are medium chain length alcohols at high hydrocarbon levels with sodium doecyl sulfate as the surfactant. Both aromatic and short chain aliphatic hydrocarbons were studied. By contrast, the amines were found virtually Ineffective with quaternary anmoniutn salts whereas the alcohols showed good performance. This suggests the possibility that complementarity of function between surfactant and cosurfactant may be a desirable feature of a microemulsion system at high hydrocarbon levels.

Microemulsions with excellent water solubilizing capacity at high hydrocarbon levels with quaternary ammonium salts as surfactants

In W/O microemulsions prepared by adding dry surfactant to a mixture of 85% heptane or toluene and 15% pentanol, then titrating with water, systems using quaternary ammonium salts have been shown to be capable of solubilizing much larger amounts of water than systems using the anionic sodium dodecyl sulfate. In homologous series in the range C12 to C16 it would appear that, with one exception, longer chain length quaternary salts are more effective at solubilizing water than are shorter chain length compounds. With quaternary salts of equal chain length, pyridinium salts are more effective at solubilizing water at high surfactant concentrations than are corresponding trimethyl salts.

Lamellar liquid crystal and other phases in the system sodium dodecyl sulfate, hexylamine, water, and heptane

Abstract Phase equilibria have been studied for the system composed of sodium dodecyl sulfate, hexylamine, heptane, and water. Greatest emphasis has been placed on the lamellar liquid crystal region and X-ray diffraction measurements. Equations are developed or modified to allow determination of the degree of penetration of water into the amphiphilic double layer as a function of water or amphiphile concentration. It is found that the interfacial area occupied by the polar or ionic head groups of amphiphiles increases with increasing water content.

Dynamic behavior in isotropic regions of tetradecylpyridinium bromide/pentanol/heptane/water system

Abstract Self-diffusion coefficients from pulsed-gradient spin-echo NMR are reported for four components of the tetradecylpyridinium bromide-85% heptane 15% pentanol-water pseudoternary system. Measurements were taken throughout the inverted microemulsion region and also in a small isotropic region beyond the domain of lamellar liquid crystals. Boundaries for the smaller isotropic region were also delineated. Observations of the self-diffusion coefficients for water relative to those of the surfactant, oil, and alcohol show several distinct structural transitions within the water-in-oil region of the phase diagram. The smaller isotropic region exhibits a complete inversion of phase relative to the water-in-oil region. Conductivity measurements were used to further clarify the NMR data.

MICROEMULS10NS WITH IMPROVED WATER SOLUBILIZATION AT HIGH OIL CONTENT

Considerations sur la solubilisation dans les microemulsions eau-huile, qui en general est proportionnellement plus faible aux concentrations elevees de la phase continue. Cas des microemulsions eau-huile stabilisees avec du bromure de myristylpyridinium en combinaison avec du pentanol (coagent de surface) presentant une capacite de solubilisation elevee

Calorimetric investigation of partitioning of alcohols between bulk and sodium dodecyl sulfate micellar pseudophases at 25°C and 45°C

Abstract A rigorous calorimetric model based on the pseudophase model at infinite diluties was employed to determine the partition coefficient and enthalpy of transfer of 1-pentanol, 3-methyl-1-butanol and benzyl alcohol between the aqueous and micellar phases of sodium dodecyl sulfate (SDDS) at 25 and 45°C. These values are in reasonable agreement with those available in the literature. The effect of temperature on the partition coefficient was found to be small, as opposed to that found for the enthalpy of transfer. An equation is derived for the limiting value of (—d ln m CMC /d m b c ) at m b c = 0 where m b c is the molality of the cosurfactant in the bulk phase. The derivation is based on a rigorous thermodynamic treatment for a pseudophase model. This constant, (—d ln m CMC /d m b c ), contains a number of terms: a partition coefficient, the degree of counter-ion binding, the Setchenov constant, the CMC and the ion—ion interaction parameter for mono-meric surfactant.

PGSE-NMR & Sans from TPB Based Microemulsions

Self-diffusion coefficients from pulsed-gradient spin-echo NMR are reported for four components of the tetradecylpyridinium bromide - 85% heptane/15% pentanol - water pseudoternary system. Measurements were taken throughout the inverted microemulsion region and also in a small isotropic region beyond the domain of lamellar liquid crystals. Observations of the self-diffusion coefficients for water relative to those of the surfactant, oil and alchohol show several distinct structural transitions within the water-in-oil region of the phase diagram. The smaller isotropic region exhibits a complete inversion of phase relative to the water-in-oil region. Conductivity measurements were used to further clarify the NMR data. Subsequent small angle neutron scattering (SANS) measurements on the same system show the transition from the single particle (heavy water + Stern layer droplet) scattering regime at low water concentration to the mixed single/interdroplet scattering regime when the intermicellar distance becomes comparable to the size of the micelles.