The interface between water and the amorphous silica surface affect both the structure and dynamics of the interfacial water molecules as well as that of the glass. For instance, diffusion, thermal expansion, hydrogen bonding, auto-ionization, and proton transport are all modified at the interface in comparison to that in bulk water. Concurrently, water ruptures siloxane bonds at the glass surface, enabling further penetration into the subsurface; water absorbed into silica affects volume changes that modify surface relaxation and fracture strength, the mechanisms of which are currently being debated within the glass community. Commonly employed non-reactive potentials in studies of the water/glass interface cannot address the realities of this interfacial behavior. In order to provide a more realistic evaluation of the behavior of water at the interface and in nanoconfinement, we use the highly accurate and transferrable reactive all-atom MG interatomic potential that matches many bulk water properties and reactions on silica surfaces as well as hydrogen bond lifetimes and proton transfer consistent with ab-initio calculations and experiment. Results show significantly higher proton transfers at the interface in comparison to bulk water, caused by extended hydrogen bond lifetimes and very low free energy barriers to proton transfer between the surface and adjacent waters and ions. Results also provide the mechanism by which nanoconfined water has a higher thermal expansion than bulk water, again caused by interfacial behavior.

Atomistic mechanisms by which the silica surface affects the properties of interfacial and nanoconfined water and water affects the properties of silica

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.