Thermal Analysis and Raman Spectra of Different Phases of the Ionic Liquid Butyltrimethylammonium Bis(trifluoromethylsulfonyl)imide
Thermal Analysis and Raman Spectra of Different Phases of the Ionic Liquid Butyltrimethylammonium Bis(trifluoromethylsulfonyl)imide
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DOI：
10.1021/jp3051824
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发表时间：
2012-08-02
影响因子：
3.3
通讯作者：
Ribeiro, Mauro C. C.
中科院分区：
文献类型：
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作者：
Faria, Luiz F. O.;Matos, Jivaldo R.;Ribeiro, Mauro C. C.
离子液体丁基三甲基铵双（三氟甲基磺酰基）酰亚胺，[C4 C1 C1 C1 N][Tf 2N]，是一种玻璃形成液体，其根据冷却速率表现出部分结晶。差示扫描量热法（DSC）表明在T-c = 227 K下结晶，在T-m = 258 K下熔融，在类似于191 K的T-g下玻璃化转变，以及在类似于219 K的T-cc下冷结晶。拉曼光谱表明，缓慢冷却得到的晶体结构是由顺式构象的[Tf 2 N]（-）形成的，而快速冷却得到的晶体结构是由反式构象的[Tf 2 N]（-）形成的。[C4 C1 C1 C1 N][Tf 2N]的缓慢或快速冷却不有利于[C4 C1 C1 C1 N]（+）阳离子的丁基链的优选构象。低频拉曼光谱表明，在过冷液体中的结晶域的发展导致在一个由微晶和非晶相的混合物的冰态。然而，通过缓慢冷却或冷结晶获得的这些晶体结构是不相同的，因为阴离子-阳离子相互作用促进具有[Tf 2N]（-）阴离子的不同构象的局部结构。
The ionic liquid butyltrimethylammonium bis(trifluoromethylsulfonyl)imide, [C4C1C1C1N][Tf2N], is a glass-forming liquid that exhibits partial crystallization depending on the cooling rate. Differential scanning calorimetry (DSC) indicates crystallization at T-c = 227 K, melting at T-m = 258 K, glass transition at T-g similar to 191 K, and also cold crystallization at T-cc similar to 219 K. Raman spectroscopy shows that the crystalline structure obtained by slow cooling is formed with [Tf2N](-) in cisoid conformation, whereas [Tf2N](-) in transoid conformation results from fast cooling. No preferred conformation of the butyl chain of the [C4C1C1C1N](+) cation is favored by slow or fast cooling of [C4C1C1C1N][Tf2N]. Low-frequency Raman spectroscopy shows that crystalline domains developing in the supercooled liquid result in a glacial state made of a mixture of crystallites and amorphous phase. However, these crystalline structures obtained by slow cooling or cold crystallization are not the same because anion-cation interactions promote local structures with distinct conformations of the [Tf2N](-) anion.