Effect of alkyl chain on micellisation properties of dodecylsulphate based surface active ionic liquids in aqueous solutions using conductance and surface tension techniques

ABSTRACT

Two surface active ionic liquids (ILs) having 1-alkyl-3-methylimidazolium cationic moiety and dodecylsulphate based anionic moiety, i.e. [C₅mim][DS] and [C₇mim][DS], have been synthesised. ¹H-NMR, thin layer chromatography was done for their characterisation. The electrical conductivity and surface tension measurements were performed to investigate the interfacial and bulk properties of the aqueous solutions of different alkyl chain ionic liquids. These techniques were employed to study the aggregation behaviour in aqueous conditions. Various surface active parameters were evaluated at 298.15 K from the surface tension measurements. The lowest surface tension (${\gamma }_{CMC}$.) and maximum surface excess concentration (${\tau }_{max}$) values showed that [C₇mim][DS] had the highest surface activity. Conductance measurements were performed at three rising temperatures (288.15, 298.15, and 308.15) K, and their thermodynamic parameters were calculated. It indicated that micellisation of both ionic liquids was entropy driven at all temperatures.

KEYWORDS:

• Micellization
• electrical conductivity
• surface tension
• surface active parameters

Acknowledgments

Council of Scientific and Industrial Research (CSIR), Government of India (Grant No. 21(1005)/15/EMR-II) financed this work through Emeritus Scientist grant to A. Pal. One of the authors, Mohit Saini also acknowledges University Grant Commission (UGC), India for an SRF research fellowship (Sr. No. 2121010033).

Disclosure statement

No potential conflict of interest was reported by the authors.

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Funding

This work was supported by the Council of Scientific and Industrial Research (CSIR) [21(1005)/15/EMR-II];UGC University Grant Commission [SRF: 2121010033];