STRESS-INDUCED DIFFUSION OF MACROMOLECULES.

A framework for analysis of stress-induced diffusion is presented. Diffusion of macromolecules is considered to be driven by gradients of entropic potential arising from distortion of the molecular conformation by deformation, as well as by gradients of entropic potential arising from distortion of the molecular conformation by deformation, as well as by gradients of concentration of individual molecular weight species. Resulting concentration profiles in circular capillary flow have been calculated for a system containing a single macromolecular species. Significant variations in concentration with capillary radius are predicted at full development. Estimates of the dynamics of development of these profiles indicate that the length to diameter ratios needed to see a measurable effect are proportional to the Peclet number, which may be quite large for macromolecular fluids depending on the geometry and flow velocity of the system. This effect may have implications in the rheology, chromatography, and technological uses of macromolecular fluids.