Surface properties, aggregation behavior and wettability of the mixed system of fluorocarbon cationic surfactant and hydrocarbon anionic surfactant in dilute solutions

Traditional perfluorooctane sulfonic acid (PFOS) fluorocarbon surfactants endangered human health and environment. Therefore, an environmentally friendly quaternary ammonium cationic fluorocarbon surfactant (PFAS-IEt) was synthesized, and surface activities, aggregation behavior, adsorption properties and wettability of PFAS-IEt/sodium n-octyl sulfate (SOS) mixtures in dilute solutions were systematically investigated. The results demonstrated that PFAS-IEt possessed excellent surface activity in aqueous solution. Surprisingly, its surface tension was only 15.33 mN/m and critical micelle concentration (CMC) was 0.002 mol/L. It could be used as a potential substitute for PFOS. In addition, PFAS-IEt had the good synergistic effect with SOS. The PTFE plate with low surface energy could be completely wetted by the binary compound solution at low concentration (0.04 mol/L) (contact angle was 0°), which was superior to the reported long chain quaternary ammonium non-ionic fluorocarbon surfactants (MN-2C9F19 and EN-2C9F19).