A dispersion force based interaction between the solvent and the beads of a bead-spring model macromolecule is used to couple the motion of the solvent and polymer in dilute solution flows. The polymer exerts a force on the solvent equal and opposite to the force that the solvent exerts on it. The friction coefficient approximation of the Rouse-Zimm theories is eliminated. Both the solvent and polymer are subject to ensemble averaging over their respective phase space. A constitutive equation for the polymer stress is presented. By appropriate selection of the interaction potential between the solvent and the polymer, any normal stress difference can be predicted.