Surfactant properties of ionic liquids containing short alkyl chain imidazolium cations and ibuprofenate anions

Interfacial tension, electrical conductivity, NMR self-diffusion and DLS experiments have been used to investigate the self-aggregation in water of ionic liquids associating an ibuprofenate anion and 1-alkyl-3-methylimidazolium C(n)MIm](+) (n = 4, 6, 8) cations. Despite the short alkyl chain on imidazolium cations (n ≤ 8), these ionic liquids exhibit particularly low Critical Aggregation Concentrations (CAC), significantly lower than their parent 1-alkyl-3-methylimidazolium chloride salts. This behaviour is attributed to the formation of catanionic pairs between ibuprofenate and imidazolium.