Colloidal flocculation in near-critical binary mixtures

Colloids suspended in a binary host close to its critical. point of demixing are considered theoretically. The colloids do not interact directly, but couple to the host degrees of freedom by preferring one of the two binary components and by decreasing the local interaction strength in the host system. Both couplings lead to flocculation, i.e., reversible aggregation of colloids, as the host critical point is approached. The flocculation is more pronounced in binary mixtures which are poor in the binary component preferred by the colloids, in accord with experimental observations.