Synthesis and characterization of gemini ester surfactant and its application in efficient fabric softening

Abstract Cationic surfactants with ester groups are considered as an important class of hydrolyzable and biodegradable materials utilized in multiple fields. In this work, a new type of gemini cationic surfactant containing two ester groups, N1,N1,N4,N4-tetramethyl-N1,N4-bis(2-(hexadecanoyloxy)ethyl)butane-1,4-diammonium bromide (TBDB), an 18-4-18 type gemini surfactant, has been successfully synthesized in a three-step reaction from natural palmitic acid, thionyl chloride, N,N-dimethylethanolamine and 1,4-dibromobutane. The maximum yield reaches about 94% under the optimum reaction conditions. The structures of the final product were characterized by FT-IR, 1H NMR and mass spectra. The critical micelle concentration (CMC) and surface tension of its aqueous solution are ~3.09 × 10−5 M and 38.4 mN/m at 25 °C, respectively, and the gemini ester surfactant shows high benzene solubilization capacity. When treating cotton fabric, it can effectively retain the whiteness and surface hydrophilicity of the fabric while exhibiting a higher fabric-softening ability than the corresponding monomeric surfactants, due to its more efficient adsorption onto the fabric surface. The discovery suggests that this kind gemini ester surfactant is promising with potential applications in the fields of surfactants and coatings.