In this work, chitosan hydrogels crosslinked by covalent-ionic and covalent bonds were obtained, and the kinetic features of their swelling in physiological saline were studied. It was found that the first-order kinetic model is the least suitable for approximating the experimental data. While the second-order model and especially the mixed swelling model best describe the experimental data. Analysis of the kinetic parameters of equilibrium swelling showed that covalent-ionic chitosan hydrogels are characterized by a high content of swelling sites and a low rate of relaxation of polymer chains in these sites. Covalent chitosan hydrogels exhibit the opposite pattern: the content of swelling sites is lower, but the relaxation rate of their chains is higher. At the same time, the contribution of water diffusion to the swelling sites increases with decreasing cross-linker concentration, and this contribution for covalent-ionic hydrogels is higher than for covalent hydrogels.
Мингалеева et al. (Thu,) studied this question.