Effects of Polymer-Grafted Silica Nanoparticles on the Freezing Behavior of Water

Nanocomposite hydrogels (NCHs) have addressed the mechanical fragility of traditional hydrogels, offering biodegradability and regeneration ability, making them suitable for use as permafrost inhibitors in Arctic soils. A key component of NCH is polymer-grafted silica nanoparticles. This study investigates how the polymer length and grafting density (the ratio of polymer chains to the surface area) affect the water-freezing behavior using coarse-grained molecular dynamics (MD) simulations. The polymer-grafted NPs are modeled as fully- or partially flexible hydrophilic polymer chains bonded to the surface of a rigid NP, while explicit water particles interact with each other using the mW model. The key characteristics such as the fundamental mechanisms of hydrogel dynamics and mechanical properties are studied alongside the spatial distribution of ice and liquid water, and freezing temperature variations. Major results suggest that an optimal grafting density is crucial for effective freezing inhibition, providing guidelines to enhance soil strength and water retention.