Hexadecyltrimethylammonium bromide (CTA-Br) and 1-butyl-3-methylimidazolium tetrafluoroborate (bmim-BF₄) in aqueous solution: An ephemeral binary system

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• 作者：Francesc Comelles ; ^{fcffte@cid.csic.es} ; Isabel Ribosa ^{irfbet@cid.csic.es} ; Juan José ; Gonzalez ^{juanj.g@gmail.com} ; M. Teresa Garcia ^{teresa.garcia@iqac.csic.es}
• 关键词：Cationic surfactant ; CTAB ; Ionic liquid ; bmim-BF4 ; CTA-BF4 ; cac ; Surface tension ; Conductivity ; Binary systems ; Synergism
• 刊名：Journal of Colloid and Interface Science
• 出版年：2017
• 出版时间：15 March 2017
• 年：2017
• 卷：490
• 期：Complete
• 页码：119-128
• 全文大小：716 K
• 卷排序：490

文摘

Mixtures of the cationic surfactant hexadecyltrimethylammonium bromide (CTA-Br) and the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (bmim-BF4) in aqueous solutions are expected to behave as typical binary cationic surfactant system taking into account the surface activity displayed by the ionic liquid, instead of considering the IL as a water cosolvent.ExperimentsSurface tension and conductivity measurements have been conducted as a function of the total concentration of the mixtures at different surfactant mole fraction (αCTA-Br) to investigate the surface active properties.FindingsTurbidity immediately appearing when the compounds are mixed in water suggests the spontaneous formation of the low soluble compound hexadecyltrimethylammonium tetrafluoroborate (CTA-BF4), together with the salt formed by the respective counterions bmim+and Br− in solution. For αCTA-Br ≠ 0.5, furthermore of the mentioned compounds, the spare bmim-BF4 (for αCTA-Br < 0.5) or CTA-Br (for αCTA-Br > 0.5), are also present in the aqueous solution. Systems containing excess of bmim-BF4 show a low critical aggregate concentration (cac), but an unexpected high surface tension at cac (γcac ≈ 53–56 mN/m), as pure CTA-BF4. For systems containing excess of CTA-Br, cac increases but γcac decreases up to 36 mN/m. Mixtures of pure CTA-BF4 and bmim-BF4 or CTA-Br behave as typical binary surfactant systems.