Influence of sodium benzoate on key colloid properties of sodium lauryl ether sulfate: Identification of a possible interfacial structure decoupler

Surfactant–oil–water (SOW) systems, particularly when packaged in metal containers, require chemical reagents with preservative and anticorrosive properties. This study aims to investigate the influence of sodium benzoate (NaBz) on fundamental interfacial properties of the surfactant lauryl ether sulfate (SLES) with two ethoxylation units (EO = 2). Using a combination of surface tension, electrical conductivity, and isothermal titration calorimetry (ITC) measurements, we evaluated SLES systems in the presence of NaCl, NaBz, and various mixtures of these salts using salinity scans, at room temperature. NaBz inhibits the formation of triphasic system in SOW formulation. The thermodynamic stability of SLES micelles followed the order: ${∆G}_{\mathrm{mic},\text{NaCl}}^0<{∆G}_{\mathrm{mic},\text{NaBz}}^0~{∆G}_{\mathrm{mic},1:1}^0<{∆G}_{\mathrm{mic},H_{2}O}^0$ with entropy being the primary driving force. The results suggest that NaBz acts as a potential interfacial structure decoupler. This novel behavior of NaBz may have important implications for its use in SOW systems, particularly in formulations requiring stability and integrity in aggregation state.