SOLVENT SORPTION IN GLASSY POLYMER FILMS COUPLING BETWEEN SOLVENT DIFFUSION AND VISCOELASTIC RELAXATION

Swelling or drying of glassy polymer films exhibit complex kinetics. For such films local thermodynamic equilibrium is no more ensured at each time since the relaxation of the stresses induced by the volume variations involves slow rearrangements of macromolecular chains. A numerical comparison of two models is presented, as a function of the two pertinent parameters describing the coupling between solvent diffusion and polymer relaxation: the Deborah number that defines the ratio between the relaxation and diffusion characteristic times, and R the ratio between the “instantaneous” and “delayed ” components of swelling. Then a numerical study of a global estimation method (SIVIA) is made, in order to estimate these parameters from weight uptake kinetics. The robustness of the estimation is analyzed according to R and the Deborah number