A THEORY OF THE FORMATION OF MICROEMULSIONS

Abstract

A mathematical model was proposed (1) in a recently published paper in an attempt to represent the formation of microemulsion systems. However, the model fits microemulsion systems only up to certain critical dispersed phase volume, known as the percolation threshold. A single total free energy minimum corresponding to a stable system was found by the model for phase volumes below the percolation threshold. If the dispersed phase volume is further increased, the model predicts instability with no free energy minimum. However, experimental results (1,2) indicate percolation of microdroplets above the percolation threshold before the system eventually breaks down upon further increase of the phase volume. An extra free energy term from the interaction between microdroplets is introduced and incorporated into the model. This new model now predicts two free energy minima above the percolation threshold of the dispersed phase corresponding to polydispersity of the system. Further increase in dispersed phase volume will then cause the system to become unstable.

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Notes on contributors

Steven Y. Chan

Present address : BASF Corp., Coatings & Inks Div. Clifton, N.J. 07105