Aggregation behavior of long-chain imidazolium ionic liquids in ethylammonium nitrate

The aggregation behavior of long-chain imidazolium ionic liquids, 1-alkyl-3-methyl-imidazolium bromide (C_nmimBr, n?=?12, 14, 16) was studied by surface tension measurements in a room temperature ionic liquid, ethylammonium nitrate (EAN), at various temperatures. A series of parameters including critical micelle concentration (cmc), surface tension at the cmc (γ _cmc), and the effectiveness of surface tension reduction (Π_cmc) were obtained. In addition, from the cmc values and their temperature dependence, we estimated the thermodynamic parameters of the micelle formation, $ Delta G_{rm{m}}^0 $ , $ Delta H_{rm{m}}^0 $ , and $ Delta S_{rm{m}}^0 $ . The contribution of enthalpy term to the micelle formation is superior to that of entropy term. ¹H NMR was performed to study the C_nmimBr micelle formation mechanism in EAN.