Conductance and fluorescent probe studies of sodium dodecyl sulfate/n-butyl alcohol/toluene brine microemulsions

Abstract

We report conductance and fluorescent probe measurements of one-phase microemulsions composed of sodium dodecyl sulfate (SDS), «-butyl alcohol, toluene, and 2.5% NaCl brine. We detected three patterns of microemulsion conductance as a function of toluene volume fraction and an interesting minimum in the pyrene excimer formation as a function of brine volume fraction. Our results imply that there are, at least, three types of microemulsions: water continuous, oil continuous, and bicontinuous. The last type forms in the vicinity of the three-phase region where the microemulsion is the middle phase. In this region, the water-to-oil ratio in the microemulsion is close to unity. In addition we suggest the existence of a water-continuous microemulsion at high toluene volume fractions in which the structure is a network of water-swollen inverse surfactant bilayers containing large discrete oil domains. M.S.R. was supported, in part, by a scholarship from CONACYT. He also acknowledges considerations from the Instituto Mexicano del Petróleo in the realization of this work.

Microstructure and Diffusion Properties of Oil-in-Water Vinyltoluene Microemulsions

“…Such transport behavior is characteristic of one can still arrive at significant values of D RO that can be used to predict the trend in microemulsions. The transport a transition from o/w to bicontinuous structure in microemulsions (18)(19)(20)(21).…”

Microemulsions studies: Correlation between viscosity, electrical conductivity and electrochemical and fluorescent probe measurements

“…1 Especially, steady-state fluorescence emission of hy-2 3 drophobic fluorescent probes has been studied in 4 order to have details concerning the microscopic prop-5 erties of microemulsions [14,17,18,32].…”

The effect of structure of oil phase, surfactant and co-surfactant on the physicochemical and electrochemical properties of bicontinuous microemulsion

“…Different experimental approaches are being employed to study the individual microemulsion phases and phase transitions [7]. These include the conductivity measurements [8][9][10][11][12][13][14][15], viscosity measurements [8,9,14], the fluorescence probe studies [15][16][17], the cyclic voltammetry [1,10,16,[18][19][20], NMR self-diffusion studies [11], and the cryo TEM studies [11]. Conductivity for example tends to decrease with decrease in the water content that is from O/W through bicontinuous to W/O phase.…”