Room-temperature ionic liquids (RTILs) constitute a new class of liquids that attract much attention because of their characteristic properties and potential utilities as functional liquids. Unique properties are remarkably manifested in their thermal behaviors such as low melting point despite being salts, hardness in crystallization, premelting over a wide temperature range, excessive supercooling, and the existence of complex thermal histories. In addition, we found peculiar thermal behaviours at the phase changes of imidazolium-based RTILs, namely ‘rhythmic melting and crystallization’, ‘intermittent crystallization’ in the premelting regions and ultraslow phase changes. These unique thermal behaviours of imidazolium-based RTILs are attributed to conformational changes and flexibility of alkyl chains bonding to the imidazolium ring.
