Classic Force Field for Predicting Surface Tension and Interfacial Properties of Sodium Dodecyl Sulfate

A classical force field capable for accurately predicting surface tensions, surface concentration, and other interfacial properties is reported for sodium dodecyl sulfate (SDS). This force field is proposed by combining parameters from well established force fields for components of the air/SDS/water interface and optimized by adjusting the van der Waals diameter of sulfate oxygen to fit experimental data of surface tension. The force field parameters are transferable; as good agreement with experimental data is achieved from independent calculations on activity derivatives of aqueous solution of sodium methyl sulfate using the Kirkwood-Buff theory. The adjusted parameter effectively modulates the electrostatic interactions of solvated ions in solutions. This modification has a strong impact to surface tension and location and mobility of sodium cations but minimal impact to properties such as density profiles of bulk phase and conformations and orientations of surfactant chain, for which consistent results compared with previous studies are obtained.