Harnessing the Potential of Amide-Linked Gemini Surfactants for Corrosion Inhibition and Antimicrobial Activity: From Molecular Design to Functional Performance

Gemini surfactants, also called Gemini, especially those with quaternary ammonium head groups, are recognized for their distinctive aggregation behavior and enhanced structure-activity relationships. The unique dual-head and dual-tail structure of Gemini grants them superior surface activity, allowing them to effectively lower surface and interfacial tension. To investigate the self-assembly behavior and surface-active properties that make them suitable as anticorrosion and antimicrobial agents, a series of cationic Gemini featuring amide bonds and varying alkyl chain lengths were synthesized. Surface activity and self-assembly characteristics of these cationic Gemini were analyzed using methods such as surface tension, electrical conductivity, fluorescence, and isothermal titration calorimetry. The findings revealed that these Gemini possess enhanced surface-active and self-assembly properties in comparison to traditional single-tail, monoheaded surfactants. Thermodynamic studies confirmed that these Gemini self-assemble spontaneously in water above a relatively low threshold concentration, with the self-assembly process becoming less favorable as the alkyl chain length decreased. The length of the chains also affected the size and shape of the aggregates formed. These Gemini have been shown to exhibit remarkable anticorrosion properties on steel surface. The performance of these compounds as corrosion inhibitors showed a clear dependence on chain length, with the shortest chain length Gemini providing the highest inhibition efficiency. These Gemini have also exhibited pronounced antibacterial activities against <i>Escherichia coli</i> (DH5alpha) and <i>Staphylococcus aureus</i> bacteria.