Towards Accurate Coarse-Grained Simulation of Sodium Laureth Sulfate(SLES) Morphology

As essential ingredients in personal care products, surfactants control product performance. To understand surfactant morphology, molecular dynamics simulation methods can provide insight at the molecular level. Moreover, a reliable and robust simulation method could guide the optimization of formulation designs in less time and in a more sustainable manner. As one of the widely used surfactants in shampoo and conditioner, sodium laureth sulfate (SLES), has been studied extensively. Simulation studies to date, however, can only predict surfactant morphology for a limited composition range and do not reflect the effects of solution conditions (e.g. salt dependence) on morphology. To improve the utility of these models across a wide composition range and incorporate the salt dependency, we adapted the MARTINI coarse-grained framework. Standard MARTINI force field parameters for these surfactants have thus far only been applied to predict aggregate size and micelle morphology at low surfactant concentrations without considering the impact of ionic strength. By reparameterizing the long range electrostatic interaction strengths, the modified MARTINI SLES models could successfully reproduce the salt dependent effects on SLES micelle morphology across a wide composition range. Micelle morphology and geometric properties were analyzed and are consistent with previous studies. This implementation of distance dependent electrostatic treatment in the MARTINI coarse-grained model has shown promising results on SLES molecules and can be extended to more complex formulations allowing for targeted design of new formulations.