Abstract:

The interfacial aggregates of anionic surfactant and hexadecane benzene sulfonate at the hexadecane-water interface were  studied by atomistic molecular dynamics simulations, and the effect of the attachment position of benzene sulfonate on the hexadecane backbone was discussed. Depending on the interface formation energy and the interfacial thickness, the 2C16-mediated system, in which the benzene sulfonate group  attached to the 2nd carbon in the hexadecane backbone, had the most energetic stable and  thickest interface. Furthermore, the arrangement of the surfactant monolayer at the interface was compared in terms of molecular interfacial area and conformational parameters. The results showed that the influence of the structure of branched alkyl benzene sulfonate was mainly attributed to the conformational alignment of the lipophilic alkyl tail for larger alkanes. As the substituted position of the benzene ring moved closer to the carbon chain endpoint, the surfactants were aligned with a smaller interfacial area, indicating stronger adsorption at the interface. As the extensibility and orderliness of the surfactants molecules increased, the interface arrangement compact more closely,which could make the surfactant correlate with a lower interfacial tension for the hexadecane-water interface and could make it easier for oil flooding.

Key words: alkyl benzene sulfonate, molecular dynamics simulation, interfacial properties, molecular conformation, oil-water interface, surfactants