(692g) Ice Formation in the Presence of Hydrogels

Antifreeze hydrogels, consisting of hydrophilic polymer networks, exhibit excellent resistance to freezing at temperatures as low as -100^oC. In recent years, they have been proposed to mitigate freeze-thaw damage in infrastructural materials in cold, Arctic regions. While there exists an abundance of experimental literature that demonstrates their functionality in subzero conditions, very few simulation studies have looked at the fundamental aspects of the freezing mechanism of hydrogels in supercooled water. Here, we use molecular dynamics (MD) simulations to investigate the effects of polymer-water interactions and crosslinking distance (polymer chain length between crosslinkers) during a slow freezing process. Our gel has a cubic lattice structure consisting of fully-flexible polymer chains connecting each crosslinker. Water is modeled explicitly in our system and uses the mW potential for their pairwise interactions. Our results indicate that amount of frozen vs unfrozen water depends on polymer hydrophobicity or hydrophilicity, and polymer crosslinking distance. Polymer interactions can dictate the type and strength of binding to water, while simultaneously, the gel introduces nanoconfinement effects where we observed the suppression of ice formation inside pore sizes of 1-3nm. We also plan on studying different sequences of hydrophobic and hydrophilic monomers, effectively introducing a range of alternating, random, or various block copolymers.