Phase behavior and heat capacities of the 1-benzyl-3-methylimidazolium ionic liquids

作者：Serra Paulo B P; Ribeiro Filipe M S; Rocha Marisa A A; Fulem Michal^*; Ruzicka Kvetoslav; Santos Luis M N B F^*

来源：Journal of Chemical Thermodynamics, 2016, 100: 124-130.

DOI：10.1016/j.jct.2016.04.009

• Drop calorimeter
• Tian-Calvet calorimeter
• Heat capacity
• Phase behavior
• Benzylimidazolium
• Ionic liquids

The thermal behavior, solid and liquid heat capacities of the 1-benzyl-3-methylimidazolium, [Bzmim](+), based ionic liquid series with Cl, PF6, BF4, CHF2CF2SO3 and NTf2 as anions were used to evaluate the effect of the insertion of an aromatic character (benzyl group) and the expected increase of the pi-pi interactions as well as the impact in the cation-anion hindrance and charge delocalization in the ionic liquid properties. It was found that the molar liquid heat capacities of [Bzmim][X] are in the same order as the 1-pentyl-3-methylimidazolium, [C(5)C(1)im][X] analogs. A good correlation between the molar (solid and liquid) heat capacity and the number of atoms of the anion was found. Two different crystalline forms for [Bzmim][BF4] differing by 10 K in the melting temperature and about 10% in the heat capacity were found. The crystallization behavior, melting temperatures, and enthalpies and entropies of fusion show that the insertion of an aromatic character (benzyl group) in the imidazolium cation leads to a significant and systematic change of the thermophysical properties of the ionic liquids associated with an increase of the glass transition and melting temperatures arising from the additional pi-pi interactions.

• 出版日期2016-9