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Synthesis, physiochemical properties, and antimicrobial activities of a novel gemini surfactants with biphenyl and multiple amide groups

Liyu Zhang, Lihua Jia, Zhenlong Zhao, Rui Yang, Jinping Wang, Xiangfeng Guo
Colloids and surfaces 2020 v.593 pp. 124628
Escherichia coli, Fourier transform infrared spectroscopy, Staphylococcus aureus, amides, ammonium chloride, antibacterial properties, aqueous solutions, biphenyl, calorimetry, carbon, electrospray ionization mass spectrometry, emulsifying, foaming, heat production, hydrogen bonding, hydrophobicity, micelles, moieties, nuclear magnetic resonance spectroscopy, stable isotopes, surface active properties, surface tension, surfactants, titration, toluene
The structure of aqueous solution surfactants, particularly the spacer group used to link the polar head groups, can significantly affect its surface activities and application properties. Herein, we designed and synthesized cationic gemini surfactants (i. e., CₙDBH, n = 12, 14, 16, 18) with biphenyl and multiple amide groups as rigid spacer and characterized their structures using ¹H NMR, ¹³C NMR, FT-IR and ESI-MS. Surface-active properties and micellization thermodynamics of CₙDBH in aqueous solution were studied by surface tension and isothermal titration calorimetry at 298.2 K. Compared to the traditional surfactant of dodecyl dimethyl benzyl ammonium chloride (1227), the synthesized cationic gemini surfactants were found to have lower critical micelle concentrations (0.494–0.00711 mmol L⁻¹) and excellent surface-tension-reducing abilities. The micellization process is thermodynamically spontaneous, exothermic and entropy-driven. Moreover, the cationic gemini surfactants show excellent foaming power and efficient emulsifying abilities for white-oil/water and toluene/water mixtures. Furthermore, they exhibit significant antimicrobial activities against Escherichia coli and Staphylococcus aureus. These excellent properties are attributed to the special molecular structure of CₙDBH, in which the four amides is more easily form intermolecular and intramolecular hydrogen bonds, while the hydrophobic biphenyl group is in favour of pointing towards the micellar core in order to interact with the long hydrocarbon chains during the assembly process. Consequently, they can potentially be applicable in a variety of fields as highly efficient agents.