Intermittent crystallization of an ionic liquid: 1-Isopropyl-3-methylimidazolium bromide

We measured the pre-melting behavior of an ionic liquid, [i-C3mim]Br, using a laboratory-made differential scanning calorimeter with nanowatt stability. A hitherto unknown behavior, intermittent crystallization, was clearly observed in the returning process of the premelting at a cooling rate as slow as 0.05 mK/s. This phenomenon occurred piece by piece in the time scale of 102 s in each domain containing ∼1014 ion pairs. By combination with our Raman spectroscopic study on the conformational changes of the [i-C3mim]+ ion, we interpret this behavior as the crystallization of locally melted domains composed of different conformers, which significantly hinders the crystallization.