Effect of Diglycerol Derivatives on Interfacial Adsorption and Micelle Properties of Potassium Dodecanoate

In this study, mixtures of potassium dodecanoate (C₁₁COOK) and diglycerol derivatives with poly(oxyethylene) (EO) or poly(oxypropylene) (PO) chains (2GlyEO₉ and 2GlyPO₉) were prepared. Their adsorption behavior at the air/water interface and aggregation properties in aqueous solution were investigated by using surface tension and small-angle X-ray scattering analyses. Our observations revealed that at concentrations above the critical micelle concentration, C₁₁COOK adsorbs and desorbs from the interface in C₁₁COOK/2GlyPO₉ and C₁₁COOK/2GlyEO₉ mixtures, respectively. A hydrophobic interaction was observed between the alkyl chain of C₁₁COOK and the PO chain of the diglycerol derivatives in the C₁₁COOK/2GlyPO₉ mixture. However, there was no interaction between the alkyl chain of C₁₁COOK and the EO chain of the diglycerol derivatives in the C₁₁COOK/2GlyEO₉ mixture. Moreover, the aggregates of the mixtures of C₁₁COOK and diglycerol derivatives collapsed in aqueous solutions, regardless of the structure of the added diglycerol derivatives due to the penetration of diglycerol derivatives with EO and PO chains into the micelles or their adsorption onto the micelle surface. Therefore, different interactions occur between C₁₁COOK and 2GlyEO₉ or 2GlyPO_9, resulting in distinct interfacial adsorption and micelle formation behaviors, especially the difference in diglycerol derivative adducts observed in interfacial adsorption. 2GlyPO₉ disrupts the C₁₁COOK micelles in solution and improves surface properties such as static and dynamic surface tension, resulting in a lower pump pressure of pump foamers.