(342ab) Obtaining the Equilibrium Adsorption Morphologies of Surfactant Molecules at Metal-Water Interfaces through Advanced Molecular Dynamics Simulations

Adsorption of surfactants on metal-water interfaces is useful for many applications, such as, in corrosion inhibition, heterogeneous catalysis, electrochemical reactions, and synthesis of anisotropic metal nanoparticles. At these interfaces, surfactant molecules are understood to adsorb in high-density adsorbed morphologies. These morphologies, however, have not been studied effectively from the current simulation techniques.

In this work, we report a new free energy sampling methodology that enables studying the formation of high-density adsorption morphologies. Using this methodology, we have studied adsorption of cationic and uncharged surfactant molecules of different alkyl tail lengths on metal-water interfaces. Our free energy calculations show that cationic molecules with small tail lengths (C-4) adsorb in a monolayer of molecules lying flat onto the surface, whereas the molecules with large tail lengths (C-12) adsorb in a mixed morphology such that some molecules lie-flat on the surface and rest of the molecules are aggregated as hemi-micelles on the surface. The uncharged molecules adsorb in much higher densely packed morphologies than cationic molecules.