ION–ION CORRELATIONS IN LIQUID DISPERSIONS

Abstract

Ion–ion correlations play an important role in liquid dispersion with strong electrostatic interactions. Examples can be found in very diverse areas with the setting of cement paste as one extreme and the compactation of DNA as another. One particularly spectacular effect of ion–ion correlations is that the traditional double layer repulsion sometimes can be converted into a net attraction. This typically takes place in the presence of multivalent counterions and/or in solutions with low dielectric permittivity. The attractive forces are driven by the energy while the repulsive are mainly of entropic origin, and the final outcome is a delicate balance of these contributions. Here we present two simple models, which give a conceptually simple description of this balance.

Keywords:

• Electric double layer
• Ion-ion correlation
• Attractive forces
• Monte Carlo simulation
• Multivalent ions
• Surfactant systems

Acknowledgments

One of a collection of papers honoring Jacob Israelachvili, the recipient in February 2003 of The Adhesion Society Award for Excellence in Adhesion Science, Sponsored by 3M.