Direct assessment of ionic liquid fragility from transport property variation at moderate temperatures

Abstract

An approach to assess the ionic liquid (IL) dynamic fragility is discussed in this work; for this, viscosity data (a transport property) of 48 ILs of different classes (aprotic, protic, surfactant and magnetic) were surveyed. The fitting approach taken here enables, for the most part, IL-viscosity data at relatively mild to moderate temperatures for precise reproduction of experimentally resolved glass transition temperatures (T_g). This, in turn, suggests that ILs are likely to be intermediate between strong- and highly fragile liquids – analogous to ionic inorganic melts such as ZnCl₂, Ca(NO₃)₂·4H₂O, or CKN (mixture of calcium and potassium nitrates).