MACROMOLECULES IN NONHOMOGENEOUS VELOCITY GRADIENT FIELDS: RHEOLOGICAL AND DIFFUSION PHENOMENA.

Rheological anomalies and migration phenomena have been observed and/or speculated upon in kinematically nonhomogeneous flows. The paper explores two alternatives to explain the phenomena, analyzing and discussing bead-spring model macromolecules with equivalent beads and linear zero-rest-length springs for the purpose. It shows how the contribution to the viscosity of the Rouse model is different in a nonhomogeneous flow than in a homogeneous flow at the same velocity gradient level. The paper examines what sort of relative motions of macromolecule and solvent are predicted by introducing nonhomogeneous kinematics into the otherwise standard bead-spring kinetic theory. Nonuniform concentration profiles develop in some, but not all, nonhomogeneous flows. Parallels are pointed out between these results and those for other types of particles.