Research on phase behavior in polymer/clay composites combined the density functional formalism for the ordering of the clay sheets with the self consistent field calculated potential for the effective clay-clay interactions within a polymer melt. The potential was integrated into the Somoza-Tarazona free energy functional for anisotropic oblate ellipsoids of revolution. The model described the phase diagram for systems that consisted of clay discs with grafted organic modifiers (surfactants) dispersed in the polymer melt. When the polymer-surfactant interaction was attractive, the effective interaction between the clay sheets became repulsive, and intercalation could occur. For a repulsive interaction between the polymers and surfactants, the effective clay-clay interaction became attractive, driving the system toward phase separation between the pure polymer and the clay. Varying the clay volume fraction and the strength of the polymer-surfactant interaction derived phase diagrams for a range of values of surfactant grafting density and length. 8 refs.