Zhiyong Hu

Synthesis and Properties of Alkyl Dibenzyl Ether Quaternary Ammonium Gemini Surfactant

Abstract Three gemini surfactants with dibenzyl ether spacer (10-B-10, 12-B-12, and 14-B-14) were synthesized and characterized. The surface activity and thermodynamic properties of micellization were determined by surface tension, steady-state fluorescence microscopy, and conductivity methods. The thermodynamic parameters of micellization (ΔmicG0, ΔmicH0, and ΔmicS0) derived from the electrical conductivity measurement implied that the micellization of these surfactants was driven by enthalpy. The enthalpy–entropy compensation of micellization showed that the stability of micelles increased with increasing alkyl chain length. Finally, we evaluated the effects of alkyl chain length on the interfacial tension, foam ability, and the emulsion stability.

Synthesis and Physicochemical Characterization of Chiral Pyrrolidinium-Based Surfactants

Chiral surfactants, (2S)-2-(hydroxymethyl)-1-methyl-1-alkyl pyrrolidinium bromides (L-CnPB, n = 12, 14, 16), were synthesized by the reaction of N-methyl-L-prolinol with long-chain alkyl bromides. The structures were characterized by IR spectra, 1H NMR, ESI-MS, and elemental analysis. Their surface activity, thermodynamic properties, and aggregation behavior were investigated by surface tension, electrical conductivity, and steady-state fluorescence. It was found that L-CnPB have lower critical micelle concentration (CMC) and surface tension at CMC (γcmc) in comparison with N,N,N-trimethyl-1-alkyl ammonium bromide (CnTAB) and N-alkyl-N-methyl pyrrolidinium bromide (CnMP). The CMC and the minimum average area per surfactant molecule (Amin) values of L-CnPB decreased with the increase in the alkyl chain length from 12 to 16. A series of thermodynamic parameters (, and ) of micellization obtained from electrical conductivity indicated that micellization is a spontaneous and entropy-driven process. Furthermore, the micelle aggregation number (Nagg) of L-CnPB obtained from steady-state fluorescence quenching was found to be 42, 48, and 53 for L-C12PB, L-C14PB, and L-C16PB, respectively. GRAPHICAL ABSTRACT

Study on the Synthesis and Surface Activities of Novel Alkyl Sulfonate Gemini Surfactants

Abstract Three novel dialkyl disulfonate gemini surfactants (Cn-6-Cn, n = 6, 8, 12; n is carbon number of hydrophobic chain) were synthesized from cyanuric chloride, aliphatic amine and taurine. The chemical structures of the prepared compounds were confirmed by 1H NMR, 13C NMR, IR spectra and ESI-MS. Their critical micelle concentrations (CMC) in the aqueous solutions at 25°C were determined by surface-tension method. With the increasing length of the hydrophobic carbon chain, the values of their CMC decreased. The surface tension measurements of Cn-6-Cn give low CMC, great efficiency in lowering the surface tension, and strong adsorption at air–water interface. In addition, adsorption and micellization behavior of Cn-6-Cn were estimated by the parameter of pC20, the minimum average area per surfactant molecule (Amin).