Multiphase Coexistence\nin an Ionic Liquid: 1‑Decyl-3-methylimidazolium\nNitrate

Complicated phase transitions were observed in a single-component\n1-decyl-3-methylimidazolium nitrate ([C<sub>10</sub>mim][NO<sub>3</sub>]) ionic liquid (IL) using Raman spectroscopy and synchrotron small-\nand wide-angle X-ray scattering (SWAXS). Time-resolved synchrotron\nSWAXS could distinguish the phase transitions depending upon the cooling\nrate. Low-<i>Q</i> peaks representing a few kinds of layered\nstructures were decomposed. Multiphase coexistence was observed in\n[C<sub>10</sub>mim][NO<sub>3</sub>] at specific cooling rates (8–9\nK/min). Ionic liquid crystals (ILCs), hybrid-layered crystals, and\nhexagonal close-packed structures coexisted simultaneously. At the\ncooling rate region, the reentrant phase transition of the ILC phase\nupon heating was observed.