Study on the Surface Properties and Aggregation Behavior of Quaternary Ammonium Surfactants with Amide Bonds

[Image: see text] A number of techniques, including conductivity, surface tension, dynamic light scattering, transmission electron microscopy, and (1)H nuclear magnetic resonance ((1)H NMR), Fourier transform infrared (FT-IR), and (1)H–(1)H 2D nuclear Overhauser effect spectroscopy ((1)H–(1)H 2D NOESY), have been used to investigate the effect of amide bonds on the interfacial and assembly properties of a cationic surfactant, N-anilinoformylmethyl-N-cetyl-N,N-dimethyl ammonium chloride (AMC-C(16)), in aqueous solutions. The adsorption of AMC-C(16) has been found to be much better than that of the conventional cationic surfactant, benzyl cetyldimethylammonium chloride (BAC-16) at the air/water interface and in solution. The surface tension measurements show the presence of two critical aggregation concentrations (CAC(1) and CAC(2)) for AMC-C(16). The presence of a strong intermolecular hydrogen bond of AMC-C(16) was confirmed by (1)H NMR and FT-TR. The molecular interactions of AMC-C(16) were detected by (1)H–(1)H 2D NOESY. The results show that the rigid group (phenyl) of AMC-C(16) was partially overlapped with its alkyl chain in aqueous solution, and the possible aggregation behavior for AMC-C(16) was proposed. The effects of an inorganic salt (NaCl) and an organic salt (C(6)H(5)COONa) to the aggregates of AMC-C(16) have been discussed.