Molecular dynamics simulation study of the adsorption of chain alkanes from solution onto graphite

Abstract

We use the molecular dynamics simulation method to study the adsorption of an n alkane from a benzene solution onto the basal plane of graphite. We show that it is possible to simulate the entire adsorption process, i.e., the diffusion of the alkanes to the surface, the penetration of the highly structured solvent layers near the surface, and the physisorption of the chains on the graphite. Specifically, we consider a solution of C14H30 in benzene confined between two graphite surfaces. The alkane chains are initially dispersed near the center of the slit where the solvent is bulklike. During the simulation, the chains are attracted by the surfaces where they adsorb replacing benzene molecules in the structured liquid near the surfaces. The alkane chains adsorb parallel to the graphite plane assuming predominately stretched conformations without tails extending into the solution. The simulation also shows evidence for the onset of self-organization due to strong lateral interactions between the adsorbed molecules.