KINETICS OF SOLVENT DIFFUSION AND SWELLING IN A MODEL ELASTOMERIC SYSTEM

We measure solvent uptake (and loss) taking place as toluene diffuses in and out of cross-linked polyisoprene spheres. We analyze our experimental data using a theoretical description of the swelling process recently put forward by two of us and use these data to test the physical assumptions at the basis of our description. We find that even though this system displays features which are commonly regarded as signature for anomalous or "non-Fickian" behavior (sigmoidal uptake), a correct use of Fick's law accounts for the evolution of the system within the limits of our experimental error. Our data analysis allows us to obtain information on the dependence of the diffusion coefficient on concentration.