Effect of Interaggregate Forces on the Size Distribution of Micelles

The size distributions of given shapes of micelles, in aqueous solutions of soap molecules, are believed to be determined primarily by amphiphile geometry and hydrophobicity. Accordingly, direct forces between the aggregates have generally been neglected. In the present paper we extend the Onsager-McMillan-Mayer theory of dilute colloidal suspensions to allow for the exchange of molecules between aggregates. By so doing we are able to describe the effects of intermicelle interactions on the size distribution of aggregates. We conclude, from simple excluded volume considerations, that these effects depend upon the shape of micelle involved, e.g., they are more important for “disks” than for ‘rods“. It is also possible, with the same formalism, to treat the effects of interaggregate forces on the formation of orientationally ordered (nematic) phases.