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

JOURNAL OF COLLOID AND INTERFACE SCIENCE

卷:490

Article

Comelles, Francesc¹  Ribosa, Isabel¹  Jose Gonzalez, Juan¹  Teresa Garcia, M.¹ 

[1] CSIC, Inst Adv Chem Catalonia IQAC, Dept Chem & Surfactants Technol, Barcelona, Spain

关键词: Cationic surfactant;    CTAB;    Ionic liquid;    bmim-BF4;    CTA-BF4;    cac;    Surface tension;    Conductivity Binary systems;    Synergism;   

DOI  :  10.1016/j.jcis.2016.11.022

来源: Elsevier

【 摘 要 】

Hypothesis: 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. Experiments: Surface tension and conductivity measurements have been conducted as a function of the total concentration of the mixtures at different surfactant mole fraction (alpha(CTA-Br)) to investigate the surface active properties. Findings Turbidity 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 alpha(CTA-Br) not equal 0.5, furthermore of the mentioned compounds, the spare bmim-BF4 (for alpha(CTA-Br) < 0.5) or CTA-Br (for alpha(CTA-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 (gamma(cac) approximate to 53-56 mN/m), as pure CTA-BF4. For systems containing excess of CTA-Br, cac increases but gamma(cac) decreases up to 36 mN/m. Mixtures of pure CTA-BF4 and bmim-BF4 or CTA-Br behave as typical binary surfactant systems. (C) 2016 Elsevier Inc. All rights reserved.

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