Solvation Thermodynamic Properties of Anionic and Natural Sulfate-Free Surfactant Molecules

Abstract

Anionic surfactants such as sodium dodecyl sulfate (SDS) and sodium lauryl ether sulfates (SLES) are commonly used to provide the cleansing action in consumer products such as shampoos and body washes. While many are harsh on skin, anionic surfactants provide these products with excellent foaming and lather characteristics that are desired by consumers. Alternatively, sulfate-free natural surfactants, including sugar-based, amino acid-based and plant-based materials, are sustainable and readily biodegradable commodities have excellent skin mildness, yet are difficult to incorporate into personal cleansing formulations because of their impact on formulation stability, thickening and rheology. In order to better understand the origin of these diverse solvation properties which results in diverse mechanisms of micellar self-assembly and dynamics we performed extensive molecular dynamics simulations and free energy calculations on the two types of surfactant molecules. In this study, we have investigated the single surfactant hydration thermodynamic properties, such as solvation entropy, enthalpy, and free energy of SDS, SLES compounds, and sulfate-free Sodium Lauroyl Sarcosinate (SLSar) to look for molecular descriptors that correlate with harshness. If successful such work could provide for rapid screening of new surfactant candidates