Molecular dynamics simulations in hydrogel research and its applications in energy utilization: A review

Hydrogels are soft, highly absorbent and water-retaining polymers that are widely used in energy utilization. Molecular dynamics (MD) simulation is powerful in exploring micro/nano mechanisms and can assist material regulation and experimental design. This review summarizes recent MD simulations on the composition and structure characteristics of physically and chemically crosslinked hydrogels, focusing on the functionalities such as mechanical properties, heat transfer performance, hygroscopic properties and photocatalytic applications required in the energy conversion process. The fundamentals of MD simulations are also introduced, along with common modeling procedures for hydrogels. Literature review showed that MD simulations can visually display molecular-scale changes during cross-linking and absorption processes, thereby predicting changes in intermolecular interactions and associated microstructural change. Challenges for future research include constructing hydrogel networks that can be experimentally verified, and developing appropriate molecular force fields under various operating conditions. Incorporating quantum mechanics or coarse-graining methods in MD simulations further broaden its application into electronic or mesoscopic problems. Combining with machine learning, finite element or lattice Boltzmann methods may be also promising as it can be used to reveal the influence of 3D pores within hydrogels. This study aims to promote the use of MD simulations in exploring characteristics and mechanisms of hydrogel and other polymer materials in energy utilization.