Enhancing surface/interface activity and wettability via trimeric surfactant-containing mixtures

The aggregation behaviors of a trimeric surfactant (Citric-3C12) in combination with anionic-nonionic surfactants of varying hydrophobic tail lengths (9-EOS/12-EOS) at different molar fractions were explored by surface tension measurements, dynamic light scattering (DLS), ζ potential analysis, and Cryo-TEM. Surface activity parameters, the interaction parameter (β), and the interfacial and micellar composition were evaluated by both the ideal mixing model and the regular solution model, with the values of β^σ and β^m found to be negative. The combination of the trimeric cationic surfactant with anionic-nonionic surfactants exhibits a pronounced synergistic effect driven by electrostatic, hydrophobic and hydrogen bonding interactions. The surface tension and critical micelle concentration (CMC) of the mixed system are significantly lower than those of the individual surfactants. Above the CMC, the surfactants form vesicles, with vesicle size tending to decrease as charge neutralization occurred. Furthermore, the adsorption behaviors of the binary mixtures were examined through surface tension, interfacial tension, and contact angle measurements. The synergistic effect is also evident in the interface adsorption behavior, where the mixed system exhibits enhanced oil-water interface activity and superior wettability on the hydrophobic surfaces.