Mapping and classification of ionic liquids in terms of glass transition and fragility

In contrast with the numerous application studies conducted on ionic liquids (ILs), systematic investigations on their glass transition thermodynamics and kinetics are relatively scarce. This study aims to map and classify typical ILs simply in terms of their glass transition temperature ( T g ), heat capacity change (Δ C p ) at T g , and fragility index ( m ) as a function of the molar mass ( M ). For 16 kinds of ILs containing cation groups such as imidazolium, pyrrolidinium, pyridinium, phosphonium, and ammonium, T g and Δ C p were determined as the representative thermodynamic parameters by performing differential scanning calorimetry (DSC) measurements. The kinetic parameter m and the ideal glass transition temperature ( T 0 ) were calculated according to the scanning rate dependence of T g . The M dependence of T g , T 0 , Δ C p , and m and the glass-forming tendency were evaluated among the 16 samples. This mapping and classification of ILs is expected to be useful for the easy prediction of the glass transition and fragility of ILs.