Effect of imidazolium-based ionic liquids on the aggregation behavior of twin-tailed cationic gemini surfactant in aqueous solution

ABSTRACT

Micellization behavior of the twin-tailed surfactants can be modulated by the addition of various modifiers. Ionic liquids (ILs) are one of them and are documented here. The beauty of these environmentally benign neoteric molecules lies in their structural versatility. Here, we have investigated the effect of three ILs: 1-butyl-3-methylimidazolium bromide ([C₄mim][Br]), 1-hexyl-3-methylimidazolium bromide ([C₆mim][Br]), and 1-octyl-3-methylimidazolium bromide ([C₈mim][Br]) on the aggregation and surface adsorption behavior of cationic gemini surfactant, bis(hexadecyldimethyl ammonium)propane dibromide (16-3-16) through experimentally measured electrical conductivities, surface tensions, and by spectral methods (UV-vis absorbance and fluorescence measurements). The main focus of the study is to observe the effect of added ILs on the critical micelle concentration (cmc), various surface parameters, aggregation number, and size of the aggregates of gemini surfactant. The results show that the more hydrophobic ILs, that is, [C₆mim][Br] and [C₈mim][Br] behave as electrolyte at lower concentration and cosurfactant at higher concentration, whereas moderately hydrophobic IL [C₄mim][Br] acts as an electrolyte at all concentration ranges studied. The modulating effects of ILs were also compared with conventional electrolyte (NaBr) at similar conditions.

GRAPHICAL ABSTRACT

KEYWORDS:

• Aggregation number
• cationic gemini surfactant
• dynamic light scattering
• ionic liquids