Recent advances of hydrogel network models for studies on mechanical behaviors

Abstract

Current constitutive theories face challenges when predicting the extremely large deformation and fracture of hydrogels, which calls for the demands to reveal the fundamental mechanism of the various mechanical behaviors of hydrogels from bottom up. Proper hydrogel network model provides a better approach to bridge the gap between the micro-structure and the macroscopic mechanical responses. This work summarizes the theoretical and numerical researches on the hydrogel network models, aiming to provide new insights into the effect of microstructure on the swelling-deswelling process, hyperelasticity, viscoelasticity and fracture of hydrogels. Hydrogel network models are divided into full-atom network models, realistic network models and abstract network models. Full-atom network models have detailed atomic structure but small size. Realistic network models with different coarse-graining degree have large model size to explain the swelling-deswelling process, hyperelasticity and viscoelasticity. Abstract network models abstract polymer chains into analytical interactions, leading to the great leap of model size. It shows advantages to reproduce the crack initiation and propagation in hydrogels by simulating chain scission. Further research directions on the network modeling are suggested. We hope this work can help integrate the merits of network modeling methods and continuum mechanics to capture the various mechanical behaviors of hydrogels. The random polymer network structure determines the macroscopic mechanical behaviors of hydrogels. This work summarizes the theoretical and numerical researches on the hydrogel network models. Full-atom network models depict the fundamental configurations of hydrogel network in atomic scale. Realistic network models based on different coarse-grain strategies have large model size. Abstract network models with much larger size are capable to not only bridge the underlying mechanism in microscale or mesoscale with the mechanical response in macroscale, but also integrate the merits of discrete methods and continuum mechanics.