Synthesis and surface activity of two trisiloxane-based sulfonate surfactants

Abstract In this work, sulfonate Gemini surfactant with two trisiloxane hydrophobic chains (2Si3SO3Na) and sulfonate surfactant with single trisiloxane hydrophobic chain (Si3SO3Na) were prepared. The structure of the surfactant was characterised by Fourier transform infrared spectroscopy, 1 H nuclear magnetic resonance and thermogravimetric analysis. Surface tension was used to study the thermodynamic parameters, such as the critical micelle concentration (CMC) and the corresponding surface tension at the CMC ( γ CMC ), of two trisiloxane surfactants. Additionally, surface tension measurements were employed to investigate the effects of temperature and inorganic salts on surface activity. The results showed that at 298 K, the CMC and γ CMC of 2Si3SO3Na were 0.24 μmol L −1 and 23.78 mN m −1 , respectively, significantly lower than those of Si3SO3Na. Dynamic Light Scattering tests indicated that the aggregate size of 2Si3SO3Na at CMC concentration was much larger than that of Si3SO3Na at its CMC concentration. Finally, wettability tests demonstrated that 2Si3SO3Na exhibited higher interfacial activity and wettability compared to Si3SO3Na.