Boundary Conditions in the Diffusion of Fluids in Swelling Polymers

Diffusion of fluids in polymers may lead to swelling, which induces stress-diffusion coupling. A simple coupling model is considered, where boundary conditions only are altered, and it leads to a sigmoidal water-uptake curve for a plate in water. Several other models are studied, which are able to induce similar sorption curves by using various boundary conditions, but comparisons between other predictions of the models reveal significant differences. Eventually, none of the models considered is able to reproduce all features of the coupling model.