Molecular Simulations of Adsorption and Self-Assembly

of Surfactants on Metal Surfaces

Dr. Sumit Sharma

Assistant Professor

Department of Chemical and Biomolecular Engineering

Ohio University

Adsorption of surfactants is a facile way of adjusting interfacial properties of metals, which has applications in electrochemistry, corrosion inhibition, heterogeneous catalysis and synthesis of anisotropic metal nanoparticles. The traditional viewpoint is that the adsorption of surfactant molecules on metals is driven by a strong affinity of the polar head group of surfactants for metals, and that surfactant molecules adsorb in a planar self-assembled monolayer (SAM). By employing atomistic and coarse-grained molecular simulations as well as statistical mechanics theory, we show that the traditional viewpoint is imprecise on many fronts. We demonstrate that the hydrophobic interactions between alkyl tails of surfactants play an active role in the adsorption process. Surfactants adsorb in various morphologies (planar SAM, cylinders and spheres) depending on their molecular geometry. Furthermore, adsorption free energy profiles of surfactants are function their aggregation state in the bulk phase – while the molecules infinite dilution strongly adsorb on to metals with no free energy barrier, surfactant micelles experience a long-range free energy barrier from the metal surface. Surfactant molecules strongly adsorb by disintegrating on the metal surface. From the knowledge of free energy profiles of surfactants at air-water and metal-water interface, we design new surfactant molecules that are expected to have better corrosion inhibition properties.

Dr. Sumit Sharma earned PhD in Chemical Engineering from Columbia University and was a post-doctoral research fellow at Princeton University. Prior to joining Ohio University, he worked as a Yield and Integration Engineer at Intel corporation. His research interests are in molecular simulations and statistical mechanics theory of soft matter, including proteins, polymers and surfactants.