title: Low-temperature heat capacity of room-temperature ionic liquid, 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.
abstract: Heat capacities of liquid, stable crystal, and liquid-quenched glass of a room-temperature ionic liquid (RTIL), 1-hexyl-3-methylimidazolium bis(trifluromethylsulfonyl)imide were measured between 5 and 310 K by adiabatic calorimetry. Heat capacity of the liquid at 298.15 K was determined for an IUPAC project as (631.6 +/- 0.5) J K(-1) mol(-1). Fusion was observed at T(fus) = 272.10 K for the stable crystalline phase, with enthalpy and entropy of fusion of 28.34 kJ mol(-1) and 104.2 J K(-1) mol(-1), respectively. The purity of the sample was estimated as 99.83 mol % by the fractional melting method. The liquid could be supercooled easily and the glass transition was observed around T(g) approximately 183 K, which was in agreement with the empirical relation, T(g) approximately ((2)/(3)) T(fus). The heat capacity of the liquid-quenched glass was larger than that of the crystal as a whole. In the lowest temperature region, however, the difference between the two showed a maximum around 6 K and a minimum around 15 K, at which the heat capacity of the glass was a little smaller than that of crystal.
authors.affiliation: National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, Tsukuba Central 3,1-1-1 Umezono, Tsukuba, Ibaraki 305-8563, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Shimizu
authors.forename: Yoko
authors.initials: Y
authors.lastname: Ohte
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Yamamura
authors.forename: Kazuya
authors.initials: K
authors.lastname: Saito
authors.forename: Tooru
authors.initials: T
authors.lastname: Atake
mesh_terms: D007093:Imidazoles / Q000737:chemistry*; D007094:Imides / Q000737:chemistry*; D052578:Ionic Liquids / Q000737:chemistry*; D013696:Temperature
chemical_list: C502489:1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide; D007093:Imidazoles; D007094:Imides; D052578:Ionic Liquids