Thermophysical Properties of Two Ammonium-Based Protic Ionic Liquids

Experimental data for density, viscosity, refractive index and surface tension are reported, for the first time, in the temperature range between 288.15 and 353.15 K and at atmospheric pressure for two protic ionic liquids, namely 2-(dimethylamino)-N,N-dimethylethan-1-ammonium acetate, [N11{2(N11)}H][CH3CO2], and N-ethyl-N,N-dimethylammonium phenylacetate, [N112H][C7H7CO2]. The effect of the anion’s aromaticity and the cation’s aliphatic tails on the studied properties is discussed. Additional derived properties, such as isobaric thermal expansion coefficient, surface entropy and enthalpy and critical temperature, were estimated.