Effects of the number of cationic sites on the surface/interfacial activity and application properties of quaternary ammonium surfactants

A novel Gemini surfactant containing four cationic sites (N,N'-bis((2-hydroxypropyl) dodecyl-tetradecyl dimethyl ammonium chloride)-N,N,N',N'-tetramethyl-N,N'-hexamethylene diammonium chloride, TC-GS) was synthesized and its structure was confirmed by FT-IR, 1 H NMR, 13 C NMR, and MALDI-TOF-MS analysis. The equilibrium/dynamic surface tension, oil-water interfacial tension, and antistatic/antibacterial properties of TC-GS were measured and compared with a Gemini surfactant containing two cation sites (Hexamethylene-1,2-bis(dodecyl-tetradecyldimethylammonium chloride, DC-GS) and a single-chain surfactant containing one cationic site (Dodecyl-tetradecyltrimethyl ammonium chloride, DTAC) to investigate the effect of the number of cationic sites on the surface/interfacial properties and application performance. The results showed that TC-GS exhibited lower critical micelle concentration (CMC) and faster dynamic adsorption rate than that of DC-GS and DTAC. And according to the measurement of oil-water interfacial tension, the TC-GS presented the superior ability to reduce the kerosene-water interfacial tension, and only of which was able to reach the ultra-low values (10 -3 mN/m) at lower concentrations. In addition, TC-GS shows better antistatic performance on polyester fabrics and has superior antibacterial ability against both Gram-negative and Gram-positive bacteria. The study reveals that quaternary ammonium surfactants containing more cationic sites are favorable to improving the surface and interfacial tension properties and application performance.