Molecular dynamics simulations have been carried out to study the microscopic properties of monolayer of monododecyl ethers of poly-oxyethylene glycol absorbed at the air/water interface. The structure-behavior relationship was investigate through the calculation of the interfacial tension. The calculated interfacial tensions with the number of ethylene oxide groups agree well with the experimental data with the error within 5 mN•m^－1. The thickness of the hydrophilic parts increased as the increasing of ethylene oxide groups while there was the maximum thickness of hydrophobic parts with six ethylene oxide groups, which are also in good agreement with the neutron reflection experiments. It is also found that the hydrophilic parts are more tilted toward the plane of the interface compared to the hydrophobic parts.

Key words: nonionic surfactant, air/water interface, molecular dynamics, interfacial tension