Investigation of the rheological properties of protic ionic liquids

This paper reports on the synthesis of five protic ionic liquids namely 2-hydroxy ethylammonium acetate, 2-hydroxy diethylammonium acetate, 2-hydroxy ethylammonium propionate, 2-hydroxy ethylammonium lactate, and 2-hydroxy diethylammonium lactate and the study of shear and temperature dependency of the viscosity at the range 313.15-343.15K. H-1 nuclear magnetic resonance and Fourier transform infrared spectroscopy spectra establish the simple ionic salt structure of these compounds. Because of their polar character, these protic ionic liquids are able to dissolve polar solvents and inorganic salts, all of them showing high tolerance into hydroxylic media. The experimental results showed that the viscosity of these fluids decreases strongly with increasing temperature, being of non-Newtonian trend over a range of shear rate. The parameters enthalpy of activation (H*), free energy of activation (G*), entropy of activation (S*), and change in heat capacity of activation (Cp*) for their viscous flow were evaluated. The temperature dependence of viscosities was fitted using the power law, Litovitz, Vogel-Fulcher-Tammann, and Ghatee equations. Copyright (c) 2016 John Wiley & Sons, Ltd.