Intermicellar interaction in surfactant solutions; a review study

The study of intermicellar interaction is of a great deal of importance regarding its fundamental effect on micellar stability as a determining criterion which affects applied aspects of micellar aggregation especially drug delivery in biological systems. This review deals with the intermicellar interaction and stability of pure and binary mixed system of conventional and gemini surfactants. Since the colloidal stability is strictly dependent upon the micelle-micelle interaction, both electrostatic and van der Waals interactions have been taken into account and discussed according to DLVO theory. The effects of miscellaneous structural parameters such as head group, chain length, and counter ion on intermicellar interaction are studied which may affect the size and shape of micellar systems determining the surface charge density. Also, the medium effects including ionic strength, temperature, electrolyte conditions such as salts and ionic liquids on intermicellar interaction have been discussed. Additionally, the effects on non-DLVO forces such as hydration, hydrophobic, and steric interactions on micellar stability have been studied. The interaction between aggregates of binary mixed systems of cationic surfactants with Triton X-100 has been reported for the first time. The hydrodynamic radius (Rh0), aggregation number, and micellar diffusion coefficient have been calculated using the linear combination theory. The electrostatic and van der Waals attraction contributions have been also calculated and their magnitude was compared indicating that the van der Waals attractive contribution is often negligible compared to repulsive electrostatic interaction.