A Molecular Dynamics Study of Ice Formation in the Presence of Hydrogels

Higher global temperatures are causing multiple freeze-thaw cycles in a year, leading to failure of infrastructural materials such as soil and cement. In recent years, polymer-based hydrogels with anti-freezing properties are being used to prolong the longevity of earthen/cementitious infrastructures. Despite the large number of experimental studies on such gels, computational literature of hydrogels undergoing a freezing process is extremely limited. Here, we use coarse-grained molecular dynamics (MD) simulations to investigate the effects of various chain lengths of a strongly-hydrophilic gel on the freezing behavior of water. We simulate a defect-free, cubic polymer lattice with either fully- or partially-flexible polymer chains connecting each permanent crosslinker. Water is explicitly included as LJ spheres following the mW model. Our results indicate that changes in freezing temperatures highly depend on polymer crosslinking density, whereas liquid water is exclusively found within gel boundaries irrespective of chain lengths. Such a computational framework can accurately predict whether antifreeze properties arise from confinement effects, or if the polymer chains uniquely hinder water’s ability to crystallize due to chemical or physical interactions.