Thermodynamics of Microemulsions: Combined Effects of Dispersion Entropy of Drops and Bending Energy of Surfactant Films


A theory of dilute microemulsions is presented which includes for the first time both the entropy of dispersion of the drops and energy effects associated with bending the surfactant films at the drop interfaces. It yields expressions for drop size for (a) a dilute microemulsion in equilibrium with an excess bulk phase, e. g. , an oil-in-water microemulsion in equilibrium with excess oil and (b) dilute oil-continuous and water-continuous microemulsions in equilibrium and containing equal amounts of surfactant. in the latter case, our theory indicates that existence of the two microemulsion phases sometimes is favored over a layered or lamellar phase, even though the ″natural curvature″ of the surfactant films is zero, corresponding to a perfectly flat film. This work is pertinent to cutting oils, pesticides, and increasing recovery of petroleum from underground reservoirs.


Chemical and Biochemical Engineering

Keywords and Phrases

Cutting Fluids; Emulsion; Microemulsions; Oil Well Production - Enhanced Recovery; Pesticides

Document Type

Article - Journal

Document Version


File Type





© 1980 Wiley-Blackwell, All rights reserved.

Publication Date

01 Mar 1980