Multiscale modeling of hydrogels

In this chapter, multiscale modeling methods for hydrogels are presented in nano-, meso-, and macroscales, respectively. In order to study the underlying mechanisms of the large deformation, energy dissipation, and fracture mechanics of hydrogels, the nanoscale modeling methods are first demonstrated through constructing their detailed atomic structure models or coarse-grained polymer network models. Methods such as molecular dynamics, coarse-grained method, and dissipative particle dynamics method have been developed to simulate their cross-linking nature, the solvent–polymer interaction and the mechanical response of the deformed polymer network. Moreover, the mesoscale modeling approaches are also essential to study the mechanical behaviors of hydrogels in terms of bridging the gaps of microscale modeling and microscale modeling. Thirdly, in continuum mechanics, the constitutive theories of hydrogels are developed based on the statistical understanding of the polymer network–water microstructure in hydrogels and thermodynamics, which can model a host of types of hydrogels under different stimuli, including but not limited to neutral gel, salt concentration–sensitive gel, pH-sensitive gel, temperature-sensitive gel, photo-thermal–sensitive gel, and magnetic-sensitive gel. In addition, finite-element methods and meshless method have been developed to predict the deformation behaviors of hydrogels based on these well-established constitutive theories.