The structure of micelles and microemulsions

Abstract

From simple micelles in water, nearly spherical aggregates of amphiphilic molecules, to bicontinuous microemulsions, oil and water microheterogeneous mixtures stabilised by a surfactant film with both local and large-scale disordered structures, the world of surfactant-containing systems is fascinating. Depending on a subtle balance of attractive and repulsive interactions between molecules at interfaces, an extraordinarily rich polymorphism of aggregated structures can be observed. After summarising the basic general constraints controlling surfactant aggregation and the formation of interfaces, different structures of micelles and microemulsions are reviewed and related to interfacial film properties and the intermolecular interactions inside them. With such systems, both static (time-averaged) and dynamic properties control structures equally well. Structures of very different systems can be described in simple ways in terms of surfactant film average curvatures and flexibility.

Influence of cholesterol on the structure of stratum corneum lipid model membrane

“…The average excess scattering-length density per unit mass ( m ) of the lipid mixtures in D 2 O was determined from the known chemical composition [37]. The calculated values are listed in Table 3.…”

Two-phase aqueous micellar systems: an alternative method for protein purification

“…When surfactant molecules are dissolved in water at concentrations above the critical micelle concentration (CMC), they form aggregates known as micelles. In a micelle, the hydrophobic tails flock to the interior in order to minimize their contact with water, and the hydrophilic heads remain on the outer surface in order to maximize their contact with water (see Figure 1) (Chevalier and Zemb, 1990;Tanford, 1980). The micellization process in water results from a delicate balance of intermolecular forces, including hydrophobic, steric, electrostatic, hydrogen bonding, and van der Waals interactions.…”

“…In particular, depending on the surfactant type and on the solution conditions, spherical micelles can grow one-dimensionally into cylindrical micelles or twodimensionally into bilayers or discoidal micelles. Micelle growth is controlled primarily by the surfactant heads, since both one-dimensional and two-dimensional growth require bringing the surfactant heads closer to each other in order to reduce the available area per surfactant molecule at the micelle surface, and hence the curvature of the micelle surface (see Figure 2) (Chevalier and Zemb, 1990;Puvvada and Blankschtein, 1990).…”

How to explain microemulsions formed by solvent mixtures without conventional surfactants

“…In ternary or quaternary mixtures containing at least one type of surfactant, the formation of microemulsions usually occurs in specific parts of the phase diagram. These macroscopically homogeneous, transparent liquids are composed of well-defined microstructures with specific signatures in scattering experiments (1). It was only recently that similar structures, designated as "pre-Ouzo," were found and characterized in ternary mixtures of two partly miscible solvents and one hydrotropic cosolvent (2).…”