Abstract
We studied melting and crystallization behaviors of some imidazolium-based ionic liquids using a laboratory-made differential scanning calorimeter (DSC) with nano-Watt stability and sensitivity. In addition to common behaviors for many ionic liquids such as pre-melting over a wide temperature range and excessive super-cooling, we observed unique thermal phenomena: reversible phase transitions of domains in the pre-melting region, rhythmic crystallization and melting, and intermittent crystallization. The last two phenomena of them were observed in the experiments at extremely slow heating/cooling rates. It is considered that they occur because an imidazolium-based cation is capable of taking plural stable conformations and the conformational changes occur linking with melting and crystallization. We interpret these curious phenomena as the phase changes of the locally melted domains composed of different conformers, which significantly hinders the phase changes.
https://ror.org/01hjzeq58 
