A non-Gaussian model for the chemo-mechanical coupling behavior of largely deformed hydrogels

A non-Gaussian model is developed to precisely describe the chemo-mechanical coupled large deformation of responsive hydrogels. In this model, the free-energy density is composed of two parts, including the elastic energy due to stretching of cross-linked polymer networks described by Gent hyperelastic model, and the mixture energy of polymer network and described by Flory–Huggins theory. The effects of junction functionality and chain entanglements are investigated by analyzing free swelling of a cubic hydrogel and constrained swelling of a blanket layer of the gel. The present model is found to exhibit obvious hardening characteristic during large deformation of the hydrogel, and the considerations of functionality of junctions and chain entanglements are essential in the coupled chemo-mechanical deformation analysis of hydrogels.