Properties of aqueous solutions of ammonium-based ionic liquids and thermodynamic modelling using Flory theory

The new protic ionic liquids mixtures properties and water are of great interest from a theoretical perspective. The objective of this study is to establish mixtures with different densities, viscosities, composition ranges and temperatures. The studied ionic liquids are N-methyl-2-hydroxy-ethylammonium acetate (m-2HEAA), N-methyl-2-hydroxy-ethylammonium propionate (m-2HEAPr) and N-methyl-2-hydroxy-ethylammonium butanoate (m-2HEAB), all based on the N-methyl-2-hydroxy-ethylammonium cation. The excess volume data are correlated using the Prigogine-Flory-Patterson equation of state (EOS) to evaluate the importance of their contributions with respect to the studied mixtures. The viscosity data were modeled combining Eyring mixture law for viscosity and excess Gibbs energy from Flory-Huggins model. The results reveal a large range of negative deviation and a non-significant contribution of the free EOS volume term compared to the interactional contribution and characteristic pressure terms. In general, the models studied in this work presented good agreement with the experimental data.