The cationic surfactants containing aromatic rings and amide bonds, N,N-dimethyl-N-dodecyl-2-pyrimidinylcarbamoylmethyl ammonium chloride (a), N,N-dimethyl-N-dodecyl-2-thiazolylcarbamoylmethyl ammonium chloride (b), and N,N-dimethyl-N-dodecylphenylcarbamoylmethyl ammonium chloride (c), were synthesized and characterized. The surface tension and conductivity values were employed to investigate the absorption and micellization behavior of the three cationic surfactants. The results showed that the synthesized surfactants have shown a low critical micelle concentration (CMC) and a high adsorption efficiency (pC 20 ) compared with the traditional cationic surfactant of N,N-dimethyl-Ndodecyl-N-benzyl ammonium chloride (BAC-12). The aromatic rings of the a, b, and c molecular structures were analyzed using the 1 H NMR spectra for electrostatic repulsion effects between hydrophilic headgroups. The size distribution of the micelles was derived using dynamic light scattering (DLS) techniques. In addition, the foaming ability of a, b, c, and BAC-12 was investigated and the antimicrobial activity of a, b, c, and BAC-12 against Escherichia coli, Staphylococcus aureus, and Bacillus subtilis was examined. The effects of amide bonds and aromatic rings on the surface properties and antimicrobial activity of a, b, and c were analyzed and compared with BAC-12 of the same alkyl chain length. The synthesized surfactants exhibited a high surface ability and better antibacterial activity compared with BAC-12.

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.

A fluorescent probe based on benzimidazole was synthesized, and its cascade recognition of PO 4 3À and

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