Structural Heterogeneities in Solutions of Triethylamine Nitrate Ionic Liquid: 1H NMR and LC Model Study

In order to uncover the micro-structural heterogeneities in solutions of ammonium based ionic liquids, triethylamine nitrate (N 222 NO 3 ) has been synthesized using acid–base neutralization and the 1 H NMR spectra of two binary mixtures, namely N 222 NO 3 /dimethyl sulfoxide (DMSO) and N 222 NO 3 /acetone at different concentrations, have been measured at 298.15 K. The internal reference method was adopted to obtain the concentration-dependent chemical shifts of –CH 3 in N 222 NO 3 , which have been correlated using the 1 H NMR local composition (LC) model to obtain the local mole fractions. It has been revealed that within N 222 NO 3 rich region, self-association of the ionic liquid was predominant instead of N 222 NO 3 –solvent interactions. However, in the solvent rich region, N 222 NO 3 mainly interacts with solvent molecules, indicating that the self-association network of N 222 NO 3 has been greatly destroyed by solvents. In addition, the different influences of DMSO and acetone have been detected. DMSO molecules more effectively destroy the original network of the ionic liquid, due to its higher dielectric constant. Also, LC behavior in N 222 NO 3 /DMSO systems is more significant than in N 222 NO 3 /acetone, indicating that DMSO can induce more obvious heterogeneities in DMSO/N 222 NO 3 mixtures, which is consistent with physicochemical properties and cellulose solubility of solutions.