Mamontov Eugene, Osti Naresh C, Ryder Matthew R
Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
Struct Dyn. 2021 Apr 5;8(2):024303. doi: 10.1063/4.0000094. eCollection 2021 Mar.
Room-temperature ionic liquids are promising candidates for applications ranging from electrolytes for energy storage devices to lubricants for food and cellulose processing to compounds for pharmaceutics, biotransformation, and biopreservation. Due to the ion complexity, many room-temperature ionic liquids readily form amorphous phases upon cooling, even at modest rates. Here, we investigate two commonly studied imidazolium-based room-temperature ionic liquids, 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, as well as their mixtures, to demonstrate how the complex interplay between the crystalline and amorphous phases is affected by the processing conditions, such as thermal history, liquid mixing, and applied pressure. We show that quantum tunneling in the cation methyl groups, measured by high-resolution inelastic neutron scattering, can be used to probe the order-disorder in room-temperature ionic liquids (crystalline vs amorphous state) that develops as a result of variable processing conditions.
室温离子液体是很有前景的候选材料，其应用范围涵盖从储能设备的电解质到食品和纤维素加工的润滑剂，再到用于制药、生物转化和生物保存的化合物。由于离子的复杂性，许多室温离子液体即使在适度冷却速率下冷却时也容易形成非晶相。在此，我们研究了两种常用的基于咪唑鎓的室温离子液体，四氟硼酸1-乙基-3-甲基咪唑鎓和双（三氟甲基磺酰基）亚胺1-乙基-3-甲基咪唑鎓，以及它们的混合物，以证明结晶相和非晶相之间的复杂相互作用如何受到加工条件的影响，如热历史、液体混合和外加压力。我们表明，通过高分辨率非弹性中子散射测量的阳离子甲基中的量子隧穿可用于探测室温离子液体中因可变加工条件而产生的有序-无序（结晶态与非晶态）。
