Catanionics: structural transition

Sanchayita Rajkhowa, Sekh Mahiuddin, Ranjit Biswas, Kochi Ismail

Department of Chemistry, North Eastern Hill University, Shillong-793022, Meghalaya, India

Email: sanchayita.rajkhowa@gmail.com

Abstract:

Aqueous mixtures of anionic and cationic surfactants, so-called catanionics, on solubilisation yield aggregates whose stability increases by adding alcohols of different chain lengths. The calorimetric patterns showed that the solubilization of the catanionics involves multiple endotherms because of different interactions of different magnitudes resulting in a multistep solubilisation [1]. The catanionics produce micelles or vesicles depending upon their compositions [2,3].  In this paper, the formation and properties of aggregates of sodium dodecyl sulphate (SDS) and cetyltrimethylammonium bromide (CTAB) mixtures at a fixed mole ratio in aqueous medium are investigated in the presence of n- propanol, isopropanol, C₃-diols and C₃-triol with particular emphasis on the size and nature of the micelle/vesicle  by  using  conductivity,  dynamic  light  scattering  and  fluorescence  spectroscopy methods. The influence of temperature on the micellization of SDS and CTAB mixtures has also been studied. The micelle-to-vesicle transition can be tuned by changing composition or temperature. Added alcohols, due to their tendency to modulate solvent properties, affect the size of the catanionic aggregates.

Keywords: Micelles, Vesicles, SDS, CTAB, Alcohols, Micelle-to-vesicle transition.

Reference:

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