Phenomenology of polymer migration

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Abstract
The diffusion mass flux in a mixture is usually written as the gradient of a chemical potential difference. When generalized to a solution of deformable polymers, this Fick's law leads to difficulties and, on the basis of a kinetic theory approach, Sekhon, Armstrong and Jones recently suggested that that part of the mass flux which depends on the polymer deformation could be written as the divergence of a second-rank tensor. Our aim here is to consider a mixture of polymers and solvent with two different velocities, and with the help of macroscopic thermodynamics, to determine the assumptions leading to each of the two proposed expressions. We then show how the Soret effect and the deformation-induced diffusion are different for the two fluxes. Thus an experimental determination of the right proposal should, in principle, be easy to perform