Swelling Behavior of Physically Cross-Linked Gelatin Gels in Varied Salt Solutions

Abstract

A series of physically cross-linked gelatin networks were prepared and the effects of salt concentration and chemical valence of the salt ions on the swelling properties of the gelatin gels were studied in detail. It was found that the swelling behaviors as polyelectrolytic or polyampholytic gels depended on the charge distribution on the gelatin chains. The swelling capacity of polyelectrolytic gels with excess positive charges decreased with an increase in salt concentrations. However, the swelling capacity of polyelectrolytic gels with excess negative charges showed a nonmonotonic change with salt concentration. For polyampholytic gels, the equilibrium swelling ratio increased monotonously with the concentration of NaCl and CaCl2 solutions. On the other hand, the swelling capacities of the polymer networks increased first and were then followed by a decrease with an increase in the concentration of AlCl3 solution. Moreover, the swelling kinetics of the gelatin gels in varied salt solutions with different concentrations was also investigated.