Molecular Dynamics Study of N-Dodecyl-N,N-Dimethyl-3-Ammonio-1-Propanesulfonate Mono-Layer Adsorbed at the Air/Water Interface

Abstract

Molecular dynamics (MD) simulation has been carried out to investigate the properties of a mono-layer of N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (SB12-3) adsorbed at the air/water interface. The simulation results show that SB12-3 can form a closely packed mono-layer at the air/water interface, the anionic sulfonic groups of the hydrophilic head group have stronger interactions with the water molecules by comparison with the cationic quaternary nitrogen of the hydrophilic head group, and water molecules can gather more easily and aggregate around the sulfonic groups. With the addition of the Ca²⁺ ions, the number of hydrogen bonds between the SB12-3 surfactant molecules and water molecules remains almost unchanged, which may explain the salt resistance behavior for SB12-3 especially for di-valent ions. The hydrophobic tail in SB12-3 is more ordered in the beginning of the chain.

GRAPHICAL ABSTRACT

Keywords:

• Aggregation
• molecular dynamics
• mono-layer
• N-dodecyl-N
• N-dimethyl-3-ammonio-1-propanesulfonate