(331g) Hydration Force Between Mica Surfaces in Li+, K+, and Cs+ Aqueous Electrolyte Solutions

The properties of aqueous electrolyte films confined between charged surfaces are important subjects in colloid science, geological science, bio-lubrication and tribology. Understanding the hydration force mechanism when aqueous electrolyte solutions are confined between two charged surfaces is critical to the development of highly efficient aqueous lubricants for nanoscale machines and biolubrication in many biological environments. In this talk we present liquid-vapor molecular dynamics (LVMD) simulations on the hydration force mechanism of 1M electrolyte solutions of LiCl, KCl, and CsCl confined between two mica surfaces. Very strong repulsive hydration forces are observed at 1-2 nm distance between two mica surfaces in K+ solution, while Li+ and Cs+ electrolytes have less repulsion compared to K+ solution, which is consistent with surface force measurements (Pashley, J. Colloid. Interface Science, 1981; Goldberg, et al., Phys. Chem. Chem. Phys., 2008). These fundamental differences come from the hydration structures of different metal ions and hydration energies associate with these metal ions.