Electric Field-Induced Interface Behavior of Dodecyl Sulfate With Large Organic Counterions: A Molecular Dynamics Study

Dodecyl sulfate with tetramethylammonium counterions has employed to systematically investigate the influence of the different static electric fields on molecular structural properties, surface tension by adopting the MD simulations with IR and SFG spectrum calculations. The results indicated that DS- and large organic TMA+ counterions can form the mixed adsorption layer of which one head group of DS- is surrounded by two TMA+ and one water molecule. Additionally, it was observed that surface tension significantly decreases with the static electric field increases since the surfactant stands straighter at the interface as the electric field increases. This result can be instructively adopted in manufactural field to control surface tension. Moreover, it was found that the SFG stretch intensities of methylene decrease and the stretch intensities of methyl increase with the increasing of the static electric fields. The result is well-demonstrated that the static electric fields will make the DS- more orderly and more upright at the interface.