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Updated: Feb 22, 2026

From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
Low-temperature and high-pressure phases of a room-temperature ionic liquid and polyiodides:
Hiroshi Abe1, Hiroaki Kishimura1, Mayumi Takaku2
1Department of Materials Science and Engineering, National Defense Academy, Yokosuka 239-8686, Japan. ab@nda.ac.jp.
Abstract:
Using simultaneous small-angle X-ray scattering (SAXS) combined with differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS) combined with DSC measurements, low-temperature (LT) solid phases of a room-temperature ionic liquid (RTIL) and its mixtures were examined at ambient pressure. The considered RTIL was 1-methyl-3-propylimidazolium iodide ([C3mim][I]), and the mixtures could be expressed as [C3mim][Im]. Under high-pressure (HP), the crystallization of pure [C3mim][I] was suppressed, as a LT-amorphous form of pure [C3mim][I] was formed. In the mixed system, the HP crystallization of [C3mim][I3] occurred at 0.95 GPa of compression. In [C3mim][I3.66] as a non-stoichiometric system, complicated phase changes were observed. Upon compression, the edge of a sample container was crystallized. By further compression, a crystal-crystal phase transition was observed as a HP-crystal polymorph appeared. In the centre, HP amorphization was observed upon compression, whereas decompression crystallization was induced by decreasing the pressure. The HP complicated behaviors of non-stoichiometric [C3mim][I3.66] are caused by the excess of iodide/iodine.
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