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.
By using the binary anionic/cationic surfactants system CH3(CH2)nOSO_3/CH3(CH2)nN+(CH3)3 as an ex-ample, the molecular exchanging energy (ε) of adsorption on the surface monolayer of aqueous solu-tion has been studied. ε can be obtained with two methods. One is from the relationship between ε and the molecule interaction parameter (β). This relationship is founded by considering that the adsorption of mixed surfactants on the surface monolayer of solution satisfies the dimensional crystal model condition under which β can be obtained by testing the surface tension of solution. The other is directly from the molecular structure of surfactants with the Lennard-Jones formula. The results for the studied system show that these two methods coincide well.
WANG ZhengWu1 & YI XiZhang2 1 Department of Food Sciences & Technology, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China
With quantum chemical parameters,topological indexes,and physical chemistry parameters as descriptors,a quantitative structure-property relationship(QSPR)has been found for the cloud points of four series of nonionic surfactants(a total of 65 surfactants).The best-regressed model includes six descriptors,and the correlation coefficient of multiple determination is as high as 0.962.
