کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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5372676 | 1504180 | 2017 | 7 صفحه PDF | دانلود رایگان |
In ionic liquids (ILs), the effects of a quaternary ammonium cation containing a hydroxyl group were investigated and compared with the effect of a standard quaternary ammonium cation. The cation possessing a hydroxyl group is choline, Chol+, and the anion is bis(trifluoromethylsulfonyl)imide, TFSIâ. Crystal polymorphism of pure [Chol][TFSI] was observed upon both cooling and heating by simultaneous X-ray diffraction and differential scanning calorimetry measurements. In contrast, [N3111][TFSI] (N3111+: N-trimethyl-N-propylammonium), a standard IL, demonstrated simple crystallization upon cooling. By adding 1-propanol or 2-propanol, the phase behaviors of the [Chol][TFSI]-based and [N3111][TFSI]-based mixtures were clearly distinguished. By Raman spectroscopy, the TFSIâ anion conformers in the liquid state were shown to vary according to the propanol concentration, propanol isomer, and type of cation. The anomalous behaviors of pure [Chol][TFSI] and its mixtures are derived from hydrogen bonding of the hydroxyl group of Chol+ cation coupled with the hydrophobicity and packing efficiency of propanol.
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Journal: Chemical Physics - Volume 491, 10 July 2017, Pages 136-142