Molecular configurations and solvation forces of confined i-tetradecane

This work is a molecular-dynamics simulation study of the influence of chain branching on the molecular configuration in confined tetradecane thin films. Simulations of layered interfacial films of n- and i-tetradecane on Pt(111) show, in contrast to experiments, that a side methyl group does not impart sufficient asymmetry to alter the solvation force law from oscillatory to non-oscillatory. Based on previous experimental findings, a novel vertical structure resembling a self-assembled monolayer, is proposed for confined, long-chain iso-alkanes. Simulations show that i-tetradecane in this structure is stable over the time scales that can be probed by molecular dynamics and that vertical films have a lower energy per molecule than layered films. With this structure, many experimental features, including the non-oscillatory solvation forces, of confined iso-alkanes are explainable and will be discussed in this paper.