Aggregation Behaviors of Dodecyl Sulfate-Based Anionic Surface Active Ionic Liquids in Water

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• 作者：Jingjing Jiao ; Bin Dong ; Huina Zhang ; Yingyuan Zhao ; Xiaoqing Wang ; Rui Wang ; Li Yu
• 刊名：The Journal of Physical Chemistry B
• 出版年：2012
• 出版时间：January 26, 2012
• 年：2012
• 卷：116
• 期：3
• 页码：958-965
• 全文大小：450K
• 年卷期：v.116,no.3(January 26, 2012)
• ISSN：1520-5207

文摘

Halogen-free, low-cost alkyl sulfate-based surface active ionic liquids (SAILs), 1-butyl-3-methylimidazolium dodecyl sulfate ([C₄mim][C₁₂SO₄]), and N-butyl-N-methylpyrrolidinium dodecyl sulfate ([C₄MP][C₁₂SO₄]) were easily synthesized through ion exchange reaction. The aggregation behaviors of [C₄mim][C₁₂SO₄] and [C₄MP][C₁₂SO₄] in aqueous solution were investigated by surface tension, electric conductivity, and static fluorescence quenching. Both [C₄mim][C₁₂SO₄] and [C₄MP][C₁₂SO₄] have rather lower cmc, 纬_cmc values and higher pC₂₀, 蟺_cmc values than those reported for the traditional ionic surfactant, sodium dodecyl sulfate (SDS), and imidazolium-based SAIL, 1-dodecyl-3-methylimidazolium bromide ([C₁₂mim]Br), with the same hydrocarbon chain length. The thermodynamic parameters evaluated from electric conductivity measurements show that the micelle formation of [C₄mim][C₁₂SO₄] and [C₄MP][C₁₂SO₄] is entropy-driven in the temperature range investigated. Lower average aggregation number indicates that the micelles of two SAILs present much looser structure. It is found that both the nature and the ring type of counterions can affect the aggregation behavior in aqueous solution. ¹H NMR results of [C₄mim][C₁₂SO₄] were used to further verify the mechanism of micelle formation. Hydration ability and steric hindrance of the imidazolium or pyrrolidinium counterion as well as the cooperative hydrophobic interaction of longer alkyl chain of [C₁₂SO₄] anion and comparatively shorter alkyl chain of [C₄mim] or [C₄MP] cation are proposed to play critical roles in the aggregation of [C₄mim][C₁₂SO₄] and [C₄MP][C₁₂SO₄].