Diffusion of polymer molecules: The need for a diffusive time scale (Q1094219)

A model system for diffusion of polymer molecules, based on a dilute solution of the Hookean dumbell-model macromolecules, is developed, and rheological constitutive equations are derived. It is shown that this model cannot determine whether nonuniform polymer concentrations occur in circular Couette flow. This implies that the constitutive equations for the polymer mass flux must be modified; this is accomplished by using the socalled migration velocity. The modified theory shows that Metzner's thermodynamic approach to polymer diffusion is incorrect [\textit{A. B. Metzner} in: Improved oil recovery by surfactant and polymer flooding, B.O. Shah and R. S. Schechter (eds.), Academic Press, New York (1977)]. This work is the first of its kind in the non-Fickian model for polymer diffusion.