Temperature dependence of non-Fickian water transport and swelling in glassy gelatin matrices.

The effect of temperature on the swelling kinetics of glassy gelatin matrices exposed to water was studied. The movement of two distinct and characteristic swelling boundaries was measured directly using an optical microscope. Swelling rate constants associated with these moving boundaries demonstrated Arrhenius behavior over the temperature range of 15 to 40 degrees C. The apparent activation energy for non-Fickian water transport into the gelatin glassy core was determined to be 8.1 kcal/mol, and 3.5 kcal/mol was found for the outer expansion of the swelling gelatin network due to water sorption. These findings are compared with activation energies for other solvent-glassy polymer systems, and possible reasons for the unexpectedly low value for non-Fickian water transport in the glassy gelatin solid are considered.