Synthesis and Performance of Double-Chain Quaternary Ammonium Salt Glucosamide Surfactants

A series of double-chain quaternary ammonium salt surfactants N-[N'[3-(gluconamide)] propyl-N'-alkyl]propyl-N,N-dimethyl-N-alkyl ammonium bromide (C_nDDGPB, where n represents a hydrocarbon chain length of 8, 10, 12, 14 and 16) were successfully synthesized from D (+)-glucose δ-lactone, N,N-dimethyldipropylenetriamine, and bromoalkane using a two-step method consisting of a proamine-ester reaction and postquaternization. Their surface activity, adsorption, and aggregation behavior in aqueous solution were investigated via measurements of dynamic/static surface tension, contact angle, dynamic light scattering, and transmission electron microscopy. An analysis of their application performance in terms of wettability, emulsifying properties, toxicity, and antibacterial properties was conducted. The results show that with increasing the carbon chain length of the C_nDDGPB surfactants, their critical micelle concentration (CMC) increased and the pC₂₀ and efficiency in the interface adsorption of the target product gradually decreased. Moreover, the influence of the hydrophobic carbon chain length on the surface of polytetrafluoroethylene (PTFE) was even greater for the wetting effect, reducing the contact angle to 32° within the length range of C8-C14. The results of the contact angle change and the wettability experiments proved that C₁₀DDGPB exhibited the best wettability. The liquid paraffin and soybean oil emulsification ability of C_nDDGPB showed an upward trend followed by a downward trend with the growth of the carbon chain, with C₁₂DDGPB exhibiting the best emulsification performance. The D_long/D_short ratio was far lower than 1, which indicates mixed-kinetic adsorption. The surfactants formed spherical micelles and showed a unique aggregation behavior in aqueous solution, which showed an increase-decrease-increase trend with the change in concentration. A cell toxicity and acute oral toxicity experiment showed that the C_nDDGPB surfactants were less toxic than the commonly used surfactant dodecyldimethylbenzyl ammonium chloride (1227). In addition, at a concentration of 150 ppm, C_nDDGPB exhibited the same bacteriostatic effect as 1227 at a concentration of 100 ppm. The results demonstrate that sugar-based amide cationic surfactants are promising as environmentally friendly disinfection products.