Polyoxyethylene Group-Dependent Surface Properties and Aggregation Behavior in Oleyl-Based Sulfosuccinate Systems

Three oleyl-based sulfosuccinates with different polyoxyethylene (EO) chain length (MS-OE_n, where <i>n</i> = 3, 5, 7) were synthesized, and their structure were confirmed using FT-IR and ¹H NMR analyses. The surfactant's adsorption properties, aggregation behavior and practical performance were systematically investigated. Equilibrium surface tension measurements elucidated the surface adsorption properties such as critical micelle concentration (cmc) values and the corresponding surface tensions at cmc (<i>γ</i>_cmc). Dynamic surface tension analysis indicated slower adsorption kinetics for surfactants with longer EO chains. Aggregation studies demonstrated that MS-OE₃ formed vesicles, whereas no such vesicular structures were observed in the aqueous solutions of MS-OE₅ and MS-OE₇ at equivalent concentrations. Further, it was observed that foam stability decreased with an increase in EO units, while MS-OE₃ exhibited the best wetting ability. Notably, the liquid crystal emulsion formulated with MS-OE₇ demonstrated exceptional long-term stability.