Applicability of lattice-based thermodynamic models to various types of hydrogel swelling behaviors

Various types of hydrogel swelling behaviors can be examined using one of two lattice-based thermodynamic models, a modified double lattice model (MDL) and a Xin model combined with the Flory-Erman theory as a contribution for network elasticity. Depending on the thermoresponsibility of the hydrogel, we investigate the swelling behaviors of lower critical solution temperature (LCST) and upper critical solution temperature (UCST) types. Hourglass, closed-loop, and LCST- and UCST-types are also hypothetically described. In addition, reentrant-type swelling behaviors are analyzed for the given hydrogel systems. The swelling equilibriums of the gel networks are calculated using predetermined molecular interaction parameters obtained from phase equilibrium of the corresponding linear polymer systems. The calculated results for the various types of swelling behaviors verify the applicability of the lattice-based thermodynamic models for swelling equilibrium of the given hydrogel systems.