Minimal and versatile description of diffusion and swelling in polymer-solvent systems: Modeling and experimental validation

The interplay between solvent diffusion and swelling of the absorbing solid leads to a variety of possible behaviors. In the case of polymer matrices, sharp penetration and swelling fronts are commonly found, with their dynamics depending on the specific features of the polymer-solvent system. Here, at the continuum mechanical level, we introduce a model to predict both concentration profile and swelling for whatever motion of the penetration front, in the one-dimensional case. A distinctive feature of our approach is that a constitutive equation for the thermodynamics of the dry side is not required. The model is validated against paradigmatic experiments available in literature, as well as through our own data (including optical microscopy) on a water–polyvinyl alcohol system. In spite of using only a small number of parameters, the model succeeds in predicting all the tested observables of the diffusion/swelling process in those polymeric systems.