Electrical Conductance Behavior of Oil-in-Water Microemulsions Stabilized by Sodium Dodecyl Sulfate and 1-Butanol

Abstract

The specific conductivity of several oil-in-water (o/w) microemulsions (MEs) stabilized by sodium dodecyl sulfate and 1-butanol was measured at 25 °C as functions of the volume fraction of oil (φ0) and the molar ratio of water to surfactant (R). The oils used are octane, benzene, toluene, carbon tetrachloride, chloroform, cyclohexane, xylene, and nitrobenzene. The conductivity data were explained by the modified Bruggeman equation in the entire experimental range of φ0 in the case of octane and nitrobenzene and in a limited range of φ0 in the case of other oils. The value of the slope of this equation, f, is found to depend on (i) the concentration of surfactant or the R value, (ii) the nature of the oil, and (iii) the nature and number of substituents, if the oil is a substituted benzene. The specific conductivity data of o/w MEs of R ) 120 and 100 were also analyzed in the light of the mixed electrolyte model, and the values of aggregation number, counterion binding constant, and radius of droplet were computed.

Ion Exchange Effects on the Electrical Conductivity of Acidified (HCl) Sodium Dodecyl Sulfate Solutions

“…11 New approaches to determine micellization parameters such as micellization constants, aggregation numbers, numbers of counterions per micelle, and critical aggregation concentrations of mixed ionic-nonionic surfactants have been recently reported. 4,[12][13][14][15] Conductivity data have also been employed to interpret changes in the structure of mixed micelles, to explain micellar effects on chemical reactivity, and to evidence formation of ion pairs between ions of interest. [16][17][18][19][20] Much less attention has been given to analyzing the conductivity of micellar systems containing two or more different electrolytes.…”

“…Electric conductivity data are typically obtained by employing common electrodes and/or ion selective electrodes, and they are most commonly used to verify the presence of aggregates and to determine the critical micellar concentration, cmc, the degree of ionization of micelles α (or the fraction of bounded counterions, β = 1 − α), ,,, and a variety of thermodynamic data . New approaches to determine micellization parameters such as micellization constants, aggregation numbers, numbers of counterions per micelle, and critical aggregation concentrations of mixed ionic−nonionic surfactants have been recently reported. ,− Conductivity data have also been employed to interpret changes in the structure of mixed micelles, to explain micellar effects on chemical reactivity, and to evidence formation of ion pairs between ions of interest. − …”

Heat capacity, conductivity, and structural changes of water-sodium dodecylsulfate-triethanolamine-1-pentanol-1,1,2,2-tetrafluorodibromoethane microemulsions

“…In order to obtain additional data on the structure of microemulsions the concentration and temperature dependences of their specific conductivity and specific isobaric heat capacity were determined. The conductivity is most often used to study the structural changes in surfactant micellar solutions and microemulsions [18,19], e.g., to find the critical concentration of surfactant micellization [20], the percolation threshold in w/o type microemulsions [18,[21][22][23][24]. It should be noted that apart from the conductivity, a change in the structure of microemulsions is usually accompanied by an abrupt change in viscosity [17,18,23], some bulk properties, the temperature coefficient of the internal pressure [24][25][26], and optical [27] properties of the microemulsions.…”

Aggregation of sodium dodecylsulfate in aqueous nitric acid medium

“…Conductivity of ionic surfactant solutions is analyzed by using the mixed -electrolyte model (MEM) described elsewhere [5][6][7][8]. However, in the earlier studies [5][6][7][8] the MEM was applied to surfactant solutions containing single counterion only, whereas in the present study we could apply the MEM to surfactant solution containing mixed counterions (sodium and hydrogen) as well. In this model, a surfactant solution is treated as a mixed electrolyte system.…”