Modeling of the swelling kinetics of hydrophilic polymer gels

The paper considers a new physico-mathematical model describing the kinetics of changes in the volume of a polymer gel granule when the concentration of the external solution changes. The model takes into account the influence of the following factors: the size of the granule, the change in the amount of water in the gel, which occurs when there is a difference in the chemical potential of the components (mainly water) inside and outside the granule, the diffusion of the solute in the granule and the relaxation of the polymer matrix to the equilibrium position under the action of elastic forces. The peculiarity of the model is the consideration of the influence of the near-surface layer formed near the surface of the polymer granule when changing the volume of the granule, which significantly affects the kinetics of the process. The possibility of applying the model to reduce the time of analysis of solute concentrations by optical micrometry is demonstrated.