Multistep phase transition in 1-decyl-3-methylimidazolium nitrate ionic liquid

Cooling-rate dependent multistep phase transition of 1-decyl-3-methylimidazolium nitrate ([C10mim][NO3]) was investigated at low temperature (LT) by conducting simultaneous small- and wide-angle X-ray scattering and differential scanning calorimetry (DSC) measurements. Above 9 ℃/min (nonequilibrium), crystallization of [C10mim][NO3] was suppressed upon cooling, whereas cold crystallization appeared upon heating. At the cooling rate region between 5 ℃/min and 8 ℃/min (quasiequlibrium), a multistep phase transition was identified on the DSC thermal traces. The Bragg reflection at the lowest scattering angle was located at a different position from that of the prepeak in the liquid state. A long periodic layered structure was formed at LT.