EXPERIMENTAL AND MODELLING OF MICELLIZATION BEHAVIOR OF BIS-2-HIDROXYETHYLAMMONIUM ALKANOATES IN AQUEOUS MEDIUM

Ionic liquids (ILs) are composed of organic salts with surfactant properties, which provides them with a wide range of applications in micelles. Consequently, several studies have investigated the micelle formation process using these elements. This work focuses on the experimental evaluation of the thermodynamic process of micelle formation and the predicting of their properties as critical micelle concentration and micellization enthalpy based on a Gibbs free energy model. The studied ILs are based on the cation bis-2-hidroxy ethylammonium and three saturated fat acid anions (caprylate (C8OOH), caprate (C10COOH), and laurate (C12COOH)) There were studied the superficial tension  and conductivities of the mixture IL + water, as well as enthalpy of the  micelle formation by isothermal titration microcalorimetry. The used model was a modified form of Nagarajan et al.¹ with the geometric characteristics of the ionic liquids are obtained using semi-empirical quantum mechanics calculations using MOPAC². The values obtained experimentally for CMCs were compatible with the results from a similar cation (cholinium) with the same anions. The model could predict the CMC values of the studied ionic liquids using no experimental data. Validation of this method offers the opportunity to analyse the micelle formation behaviour in a set of ILs without the demand for exhaustive and expensive experiments. This advance opens new perspectives to expand the generation of data on the micellization of ionic liquids, representing a significant contribution to the scientific area.

¹Nagarajan, R. In Surfactant Science and Technology: Retrospects and Prospects, L. Romsted (Ed.), Taylor and Francis, New York, 2013

²MOPAC2016, James J. P. Stewart, Stewart Computational Chemistry, Colorado Springs, CO, USA, available in HTTP://OpenMOPAC.net, 2016, Consulted in  October 2nd, 2023.