Anion effect on the aggregation behavior of the long-chain spacers dicationic imidazolium-based ionic liquids

作者：Frizzo Clarissa P; Bender Caroline R; Gindri Izabelle M; Salbego Paulo R S; Villetti Marcos A; Martins Marcos A P

来源：Colloid and Polymer Science, 2015, 293(10): 2901-2910.

DOI：10.1007/s00396-015-3680-y

• Dicationic ionic liquids
• Aggregation
• CAC
• Anions
• Hydrophobicity

This work reports the study of the anion effect on the aggregation behavior of the long-chain spacers of dicationic imidazolium-based ionic liquids (ILs) in a 4.75 % (v/v) ethanol-water solution as well as in ethanol (95 %). The anions studied were Br-, NO3 (-), BF4 (-), SCN- and NTf2 (-). Aggregation behavior was investigated by differential scanning calorimetry (DSC), conductivity, surface tension, and fluorescence. In the ethanol-water solution, the critical aggregation concentration (CAC), free energy aggregation (a dagger GA degrees(a)), and the ionization degree (alpha) all significantly decreased with the increase in anion hydrophobicity. In ethanol, the CAC and a dagger GA degrees(a) values also decreased with the increase in anion size and hydrophobicity. The free energy adsorption (a dagger GA degrees(ads)) data showed that the dicationic ILs have good surfactant activity, and this property improved with the decrease in the hydration radius of the anions. The anion volumes calculated also showed a good correlation with the CAC values for aggregation in ethanol-water solution and ethanol.

• 出版日期2015-10