Effect of additives on the surface active and morphological features of 1-octyl-3-methylimidazolium halide aggregates in aqueous media

The influence of two salts as additives namely sodium chloride and sodium sulphate and a nonelectrolyte, 2-butoxyethanol on surface chemical and aggregation characteristics of ionic liquids (IL) of 1-octyl-3-methylimidazolium chloride, [C8mim][Cl], 1-octyl-3-methylimidazolium bromide, [C8mim][Br], and 1-octyl-3-methylimidazolium iodide, [C8mim][I] in aqueous media were monitored through surface tension and small angle neutron scattering measurements. The addition of salts drastically decreased the critical aggregation concentration (CAC) and increased the area per adsorbed IL molecule. The co-ions of salts modify the surface of IL molecules and aggregates through various interactions such as charge neutralization, specific interactions and dehydration The results obtained by analyzing the SANS curves in the whole Q range showed that the oblate ellipsoidal shape of the aggregates of ionic liquids is un-altered upon the addition of additives. However the additives facilitate the growth of the aggregates in to microstructures with cubic packing at high salt concentrations.

Figure optionsDownload as PowerPoint slideResearch highlights▶ The amphiphilic ionic liquids form oblate ellipsoidal aggregates in water. ▶ The sodium chloride, sodium sulphate and 2-butoxyethanol promotes aggregate growth. ▶ The co-ions modify the electrochemical and hydration characteristics of aggregates. ▶ The microstructure of larger aggregates is made up of cubic packing of molecules.