Viscosity, surface tension, and density as well as molar volume and expansion coefficient of imidazolium based amino acid ionic liquids (AAILs) including alaninate ([ALA] -), glycinate ([GLY] -), glutamate ([GLU] -), serinate ([SER] -), and valinate ([VAL] -) anions were investigated at the extended temperature until 373.15 K. Raising the temperature resulted in a downward trend on the density, viscosity, and surface tension of all systems. In addition, the hypothetical critical temperatures of the AAILs were estimated making use of the Eötvos and Guggenheim equations. The results revealed that the critical temperature decreases with alkyl chain length and [EMIM][GLY] had the highest critical temperature. Investigating viscosity as a transport property demonstrates that the lowest viscosity is observed for AAILs involving [GLY]- anion that is described by high flexibility of the anion; besides, its sharply varying with surface tension was studied. Finally, the change in volume of AAILs is small as the temperature increases confirming AAILs as solvent do not expand much which explains their good solvent characteristics.

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