A Comprehensive Study on the Synthesis and Micellization of Disymmetric Gemini Imidazolium Surfactants |
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| Authors: | Xiaohui Zhao Dong An Zhiwen Ye |
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| Affiliation: | 1.School of Chemical Engineering,Nanjing University of Science and Technology,Nanjing,People’s Republic of China |
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| Abstract: | Two groups of disymmetric Gemini imidazolium surfactants, C14C4C m im]Br2 (m = 10, 12, 14) and C m C4C n im]Br2 (m + n = 24, m = 12, 14, 16, 18) surfactants, were synthesized and their structures were confirmed by 1H NMR and ESI–MS spectroscopy. Their adsorption at the air/water interface, thermodynamic parameters and aggregation behavior were explored by means of surface tension, electrical conductivity and steady-state fluorescence. A series of surface activity parameters, including cmc, γ cmc, π cmc, pC 20, cmc/C 20, Γ max and A min, were obtained from surface tension measurements. The results revealed that the overall hydrophobic chain length (N c) for C14C4C m im]Br2 and the disymmetry (m/n) for C m C4C n im]Br2 had a significant effect on the surface activity. The cmc values decreased with an increase of N c or m/n. The thermodynamic parameters of micellization (ΔG m θ , ΔH m θ , ΔS m θ ) derived from the electrical conductivity indicated that the micellization process of C14C4C m im]Br2 and C m C4C n im]Br2 was entropy-driven at different temperatures, but the contribution of ΔH m θ to ΔG m θ was enhanced by increasing N c or m/n. The micropolarity and micellar aggregation number (N agg) were estimated by steady-state fluorescence measurements. The results showed that the surfactant with higher N c or m/n can form larger micelles, due to a tighter micellar structure. |
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| Keywords: | Disymmetric Gemini imidazolium surfactants Synthesis Surface activity Thermodynamic parameters Micropolarity Aggregation number |
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