Generalized diffusion model for viscoelastic mixtures

Diffusional processes in polymeric mixtures are often governed by the structural relaxation of the macromolecular chains.
Due to high molar masses, the polymeric component fails to respond instantaneously to incoming solvent molecules. In
fact, the relaxation process is overlaid to translational diffusion of the absorbed species and turns out to be the ratedetermining
step in many cases. Ignoring this relaxation kinetic leads to concentration- and even time-dependent diffusion
coefficients. This work addresses and solves this issue by incorporating the virtue of the relaxation process into the
chemical potential of the solvent, enabling quantification the kinetics of both diffusion and relaxation, using established
concepts for diffusion modelling.