Theoretical study of the role of head-group interactions in the micellization of non-ionic surfactants

Abstract

The critical micelle concentration (c.m.c.) and various properties of amphiphiles in solution have been simulated for a simple parametrization of the free energy of formation of micelles in terms of their aggregation numbers. A simple expression for the dependence of the c.m.c. on the energy parameters is obtained empirically from the numerical determinations of the c.m.c. The criterion used for the c.m.c. is that the rate of change of monomer concentration with respect to total amphiphile concentration is at a maximum. This is compared with the results of an alternative expression based on a horizontal inflection point in the micelle size distribution (the Ruckenstein–Nagarajan criterion).

Numerical results are scaled to highlight the effect of headgroup interactions, and experimental light-scattering results are simulated for a variety of systems.