Molecular dynamics simulations of tethered alkane chromatographic stationary phases

We present molecular dynamics simulations of intermediate density disordered alkane monolayer systems tethered to model silica surfaces. The densities and chain lengths studied are typical of reversed phase liquid chromatography (RPLC) stationary phases. The simulations are used to elucidate at the molecular level the complicated nature of the structure and dynamics of the stationary phases, which may critically affect the retention mechanisms of RPLC. We examine temperature, chain length, chain density, and surface structure effects on the chain properties. Also, we explore the driving forces responsible for observed interfacial ordering of the chain system in relation to previous simulations and analytical theories. An attractive surface potential and an attractive interparticle potential are both necessary to obtain the structure with the most realistic features. A corrugated surface perturbs the chain density profile relative to that on a flat surface but does not appreciably affect the dynamics of the chains.