Swelling Kinetics\nof Hydrogel Beads in Aqueous Glycerin\nSolutions

This study examines the swelling kinetics of polyacrylamide\nhydrogel\nbeads in aqueous glycerin solutions of different concentrations. The\ntotal absorbed mass of the hydrogel beads remains nearly constant,\nindependent of glycerin concentration, but the swelling process is\nmarkedly slower with increasing glycerin concentration in the aqueous\nsolutions. Absorption capacity curves exhibit universal kinetics when\ntime is rescaled using a characteristic time proportional to the viscosity\nof the solutions. Additionally, a novel visualization technique is\nemployed to observe the core–shell structure of the hydrogel\nbeads at early times in the swelling process. The evolution of the\ncore–shell structure indicates a constant front velocity, which\nalso reveals universal behavior with the same nondimensional time,\nsuggesting a viscous dominated transport of the solution penetrating\nthe beads.