Investigating the Distribution of Potassium Perfluoro (2-Ethoxyethane) Sulfonic Acid in Water/Gas Systems using Molecular Dynamics Method

Abstract

Molecular dynamics method (MD) was used to study the distribution of potassium perfluoro (2-ethoxyethane) sulfonic acid (PESK) in water/gas systems. During the MD process, PES − spontaneously moves to the water surface, which is also the principle by which surfactants act. At equilibrium, most of the fluorocarbon chain faces the gas phase while the sulfonic acid radical faces the water, with a very small quantity of PES − and K + is still in the bulk solution. The distribution of quantity density and charge density both confirm that PES − is mainly distributed at the water/gas interface. Weak intermolecular interactions were analyzed using the IGMH method, with the main interaction energy between PES − and water coming from h-bonds formed by the oxygen atom in the sulfonic acid group and hydrogen atom in water molecules. There is only van der Waals interaction between K + and H2O molecules. The strength of the interaction between surfactants and water molecules was studied through energy decomposition.