Abstract Mixtures of ionic liquids (ILs) with molecular cosolvents are attracting increased attention for the development of their technological applications. As a result, understanding the interaction between the heterogeneous structure… Click to show full abstract
Abstract Mixtures of ionic liquids (ILs) with molecular cosolvents are attracting increased attention for the development of their technological applications. As a result, understanding the interaction between the heterogeneous structure of ILs and molecular cosolvents at a microscopic level with the aim of fine-tuning the properties of ILs is of utmost importance. In this study, the local structure of the IL 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([bmim][TFSA]) in a series of mixtures of primary alcohol (from methanol to 1-dodecanol) is investigated as a function of alcohol concentration by Raman spectroscopy, providing a unique picture of the evolution of the local structure of alcohol clusters formed in [bmim][TFSA]. The Raman spectra reveal the presence of various types of O H species in the [bmim][TFSA]–alcohol mixtures, with the major fractions corresponding to monomers at lower alcohol concentrations. Presented in this study is a plausible mechanism for the filling of the nanoheterogeneous structures of the [bmim][TFSA] matrix by alcohol molecules, revealing the occurrence of conformational changes in the bmim+ cation and TFSA− anion, which involves an increase of the population of the gauche and transoid conformers with alcohol concentration. Interestingly, the results show that the local structures of bmim+ and TFSA− cooperatively change along with the conformational change in the alcohol molecules toward a smaller total volume.
               
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