Raman Spectroscopy of Ionic Liquid [BMIM][TFSI] at Low Temperature
Journal Title: 河南科技大学学报（自然科学版） - Year 2017, Vol 38, Issue 5
Abstract
The temperature-induced phase transition and molecular conformation of the imidazole ionic liquid 1-butyl-3-methylimidazolium bis{ ( trifluoromethyl) sulfonyl} imide ( [BMIM][TFSI]) was studied by differential scanning calorimetry ( DSC) and raman spectroscopy. The results show that the sample remains liquid state when cooling down from room tempenture to 190 K. Fuether cooling to 184 K, the super-cooling liquid sample transforms into the glassy state. During the warming process, the exothermic peak appears at about 240 K, and new Raman peaks appear, indicating that [BMIM][TFSI] changes from a disordered structure to an ordered crystalline phase. When the temperature rises to about 270 K, [BMIM][TFSI]melts back to the initial liquid state, indicating that the process is reversible. The quantitative analysis of the Raman peaks of the molecular conformation shows that both the trans and cis conformations coexist at room temperature, but the proportion of the trans conformation increases as the temperature decreases. With increasing temperature, the trans conformation disappears with the transformation of the crystalline state at 240 K, indicating that the crystal obtained by cold crystallization has only cis conformation.
Authors and Affiliations
Jie WU, Fengchun JIANG, Xiang ZHU, Junyu LI
Keywords
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