title: Melting and freezing behaviors of prototype ionic liquids, 1-butyl-3-methylimidazolium bromide and its chloride, studied by using a nano-Watt differential scanning calorimeter.
abstract: 1-Butyl-3-methylimidazolium bromide ([bmim]Br) and its chloride ([bmim]Cl) are representative prototypes of ionic liquids. We investigated the melting and freezing behaviors of [bmim]Br and [bmim]Cl by using a homemade differential scanning calorimeter (DSC) with nano-Watt stability and sensitivity. The measurements were carried out at heating and cooling rates slow enough to mimic quasi-static processes. Their thermal behaviors of melting and freezing show characteristic features such as a wide pre-melting range and excessive supercooling and individual behaviors of single crystals even for the same substance. The melting temperatures of [bmim]Br and [bmim]Cl were determined from the broad DSC traces and discussed in relation to the crystal structure. We suggest that the observed characteristics are due to the dynamics of the cooperative change between gauche-trans (GT) and trans-trans (TT) conformations of the butyl group in the [bmim]+ cation.
authors: Graduate School of Science and Technology, Chiba University, Yayoi, Chiba, 263-8522, Japan. k.nishikawa@faculty.chiba-u.jp
authors: Keiko
authors: K
authors: Nishikawa
authors: Shaolan
authors: S
authors: Wang
authors: Hideki
authors: H
authors: Katayanagi
authors: Satoshi
authors: S
authors: Hayashi
authors: Hiro-o
authors: HO
authors: Hamaguchi
authors: Yoshikata
authors: Y
authors: Koga
authors: Ken-ichi
authors: K
authors: Tozaki
mesh_terms: D002152:Calorimetry, Differential Scanning / Q000295:instrumentation / Q000379:methods*; D007093:Imidazoles / Q000737:chemistry*; D052578:Ionic Liquids / Q000737:chemistry*; D015394:Molecular Structure; D012680:Sensitivity and Specificity; D013696:Temperature
chemical_list: D007093:Imidazoles; D052578:Ionic Liquids; C502841:1-butyl-3-methylimidazolium chloride