Molecular dynamics simulations of surfactants at the silica-water interface: anionic vs nonionic headgroups

Understanding surfactant adsorption on surfaces at the molecular level will provide us with the ability to design specific surfactants for surface modification. We conducted molecular dynamics simulations for sodium dodecyl sulfate (SDS) and hexaethylene glycol monododecyl ether (C(12)E(6)) adsorbed on silica substrates with varying degree of hydroxylation. Our results shed light on the effects of hydroxylation on the surfactant aggregate morphology. The discrete charge distribution on the substrate surface appears to dictate both surfactant adsorption and aggregate morphology. The differences in aggregate morphology observed for anionic SDS and non-ionic C(12)E(6) on silica substrates are discussed quantitatively and compared to available experimental data.