Application of the significant structure theory for the viscosity modeling of ionic fluids

The present work introduces the application of a modified significant structure theory (SST) in order to obtain improved representations of the dynamic viscosity of several representative last-generation ionic fluids: pure ionic liquids (ILs) and deep eutectic solvents (DESs). The activated-state variables present in the resulting SST-based model were related to well-known thermodynamic potentials (residual internal energy, liquid and solid molar volumes) which in turn were estimated from two simple cubic equations of state of the van der Waals type: Soave-Redlich-Kwong or Peng-Robinson. The modifications introduced to the SST approach were successfully verified during the correlation and prediction of experimental dynamic viscosities of 3 families of imidazolium-based ILs ([C_Xmim][BF₄], [C_Xmim][PF₆] and [C_Xmim][Tf₂N]), one pyridinium-based IL ([b3mpy][BF₄]), one pyrrolidinium-based IL ([P14][Tf₂N]), one ammonium-based IL ([N1114][Tf₂N]) and four ILs having nonfluorinated anions ([dmim][MeSO₄], [bmim][EtSO₄], [bmim][Ac] and [b3mpy][dca]) over a temperature range varying from 273.15 to 438.15 K and at pressures from 1 to 3,000 bar We also considered three archetypal choline chloride-based DESs for model validation: Reline, Ethaline and Glyceline within a temperature range varying from 293.15 to 373.15 K and at pressures from 1 to 1,000 bar