Thermodynamic Properties of [C₆mim][NTf₂] in the Condensed State

Abstract

Heat capacities of 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C6mim][NTf2] have been measured with a new adiabatic calorimeter in a range of temperatures of (5 to 370) K. The substance was found to form glass with Tg = 184.3 K and Cs,m = (170.7 ± 2.8) J·K-1·mol-1. At different modes of crystallization [C6mim][NTf2] forms at least three crystals, the heat capacities of which differ up to 2 % in the temperature range of (220 to 250) K but coincide within 0.1 % in the temperature range of (80 to 220) K. Triple-point temperature for all the crystals is T0 = (272.03 ± 0.01) K, but the enthalpies of fusion are somewhat different. Thermodynamic properties for [C6mim][NTf2] are calculated based on the obtained data.