Investigation of adsorption of surfactant at the air-water interface with quantum chemistry method

Density functional theory (DFT) of quantum chemistry was used to optimize the configuration of the anionic surfactant complexes CH3(CH2)7OSO?3 (H2O)n (n=0―6) and calculate their molecular frequencies at the B3LYP/6-311+G* level. The interaction of CH3(CH2)7OSO?3 with 1 to 6 water molecules was inves-tigated at the air-water interface with DFT. The results revealed that the hydration shell was formed in the form of H-bond between the hydrophilic group of CH3(CH2)7OSO?3 and 6 waters. The strength of H-bonds belongs to medium. Binding free energy revealed that the hydration shell was stable. The in-crease of the number of water molecules will cause increases of the total charge of hydrophilic group and S10-O9-C8 bond angle,but decreases of the alkyl chain length and the bond lengths of S10-O11,S10-O12 as well as S10-O13,respectively.