Synergistic effects of Gemini cationic surfactants with multiple quaternary ammonium groups and anionic surfactants with long EO chains in the mixed systems

In this study, two different anionic surfactants containing long polyoxyethylene chains involving sodium fatty alcohol ether carboxylates (AE9C) as well as isomeric sodium fatty alcohol ether sulfates (iso-AE9S) are mixed with a new Gemini cationic surfactant bearing four quaternary ammonium groups (TC-GS). Then, the surface properties and aggregation behavior of the two mixed systems were investigated. The effect of the long polyoxyethylene chains on the conformation and hydration of the hydrophilic head group of AE9C and iso-AE9S weakened their negative charge density, thus hindering their excessive elec- trostatic adsorption with TC-GS and improving the stability of the mixed systems. The positive synergis- tic effects of TC-GS/AE9C and TC-GS/iso-AE9S exhibited significantly lower critical micelle concentration, faster diffusion rates, and superior wetting capability compared to single surfactants. The micellization process of both mixed systems is spontaneously enthalpy-driven, and the diffusion-adsorption process is consistent with the mixed diffusion-kinetic mechanism. Finally, both mixed systems are capable of forming complex and interesting aggregate morphologies, with TC-GS/AE9C can form multilayer spheri- cal vesicles and TC-GS/iso-AE9S can form multicompartment concentric spherical vesicles.(c) 2023 Elsevier B.V. All rights reserved.

Automated summary

This study investigates the surface properties and aggregation behavior of mixed systems containing two different anionic surfactants and a new cationic surfactant. The presence of long polyoxyethylene chains weakens the negative charge density of the hydrophilic head groups, leading to enhanced stability of the mixed systems. The mixed systems exhibit lower critical micelle concentration, faster diffusion rates, and superior wetting capability compared to single surfactants.