van der Waals forces in electrorheological fluids

It is well known that dipole-dipole forces (induced by external electric fields) between colloidal particles play a central role in determining the thermodynamic phases of electrorheological fluids. Here, it is argued that the long-range van der Waals forces induced by photon exchange also play an important role. A theory, which quantitatively includes the van der Waals interactions, is developed using statistical thermodynamic mean-field approximations. A comparison with an experimental phase separation is shown to be satisfactory.