Formation and Morphology of Reverse Micelles Formed by Nonionic Surfactants in “Dry” Organic Solvents

Title:Formation and Morphology of Reverse Micelles Formed by Nonionic Surfactants in “Dry” Organic Solvents

Volume: 14 Issue: 6

Author(s): Sofía V. Pérez, Andres F. Olea and M. Pilar Gárate

Affiliation:

Keywords: Reverse micelles, nonionic surfactants, non-polar solvents, NMR.

Abstract: The formation of reverse micelles by nonionic alcohol ethoxylates surfactants in two “dry” non polar solvents, heptane and dibutoxymethane (DBM), has been studied. These surfactants are formed by a linear hydrocarbon chain consisting of i carbons, and a poly(ethylene oxide) chain with j ethoxylate units (EO) ending with a hydroxyl group, C_iEO_j. The study is focused on the determination of the critical micelle concentration CMC and the size and morphology of the formed aggregates. The CMC was obtained from the decreasing of interfacial tension with increasing surfactant concentration and by using pyrene sulfonic acid sodium salt as fluorescence probe. The results show that the CMC in heptane is one order of magnitude higher than in DBM and two orders of magnitude higher than those determined in aqueous solution. The self-diffusion coefficients D of C₈EO₅, C₈EO₄ and C₁₀EO₆ in heptane, were obtained by diffusion ordered spectroscopy (DOSY ¹H-NMR). The experimental values of D were then fitted to four different configurations to determine the most probable morphology of the formed aggregates. In all cases the presence of large and compact aggregates, with aggregation numbers going from a few dozens of monomers to a hundred of them, was shown.

Cite this article as:

Pérez V. Sofía, Olea F. Andres and Gárate Pilar M., Formation and Morphology of Reverse Micelles Formed by Nonionic Surfactants in “Dry” Organic Solvents, Current Topics in Medicinal Chemistry 2014; 14 (6) . https://dx.doi.org/10.2174/1568026614666140118222419