Self-Assembly and Thermal Stability of Ether-Functionalized Imidazolium Ionic Liquids

A series of short-chain ionic liquids with N-methylimidazolium headgroup have been synthesized and investigated for their self-aggregation behavior in aqueous medium by conductivity, surface tension, and fluorescence techniques. Structure elucidation of these ionic liquids has been done by NMR and mass spectroscopy. Physicochemical parameters such as critical aggregation concentration (cac), surface tension at the cac (gamma(cac)), adsorption efficiency (pC(20)), effectiveness of surface tension reduction (Pi(cac)), saturation adsorption (tau(max)), and minimum surface area/molecule (A(min)), Gibbs free energy of the aggregation (Delta G degrees(agg)) and Gibbs free energy of adsorption (Delta G degrees(ads)) at the air water interface of these ionic liquids have been measured. The adsorption and self-aggregation behavior of these short-chain cationics have been found to be better than those of conventional short-chain cationics. Dynamic light scattering (DLS) experiments have provided insights about the size of the aggregates. The thermal stability of these ionic liquids has also been evaluated by using thermal gravimetric analysis (TGA).