Rheology of Imidazolium-Based Ionic Liquids with Aromatic Functionality

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• 作者：Ran Tao ; Sindee L. Simon
• 刊名：Journal of Physical Chemistry B
• 出版年：2015
• 出版时间：September 3, 2015
• 年：2015
• 卷：119
• 期：35
• 页码：11953-11959
• 全文大小：478K
• ISSN：1520-5207

文摘

A series of imidazolium-based ionic liquids with cyclic and aromatic groups and a bis[(trifluoromethane)sulfonyl]amide anion were characterized using dynamic and steady shear rheology in a wide temperature range. The cations investigated include 1-(cyclohexylmethyl)-3-methylimidazolium ([CyhmC₁im]⁺), 1-benzyl-3-methylimidazolium ([BnzC₁im]⁺), 1,3-dibenzylimidazolium ([(Bnz)₂im]⁺), and 1-(2-naphthylmethyl)-3-methylimidazolium ([NapmC₁im]⁺). Rheological properties are reported from terminal flow to the glassy state. All ionic liquids show very similar flow behavior with a glassy modulus approaching 1 GPa. The temperature dependences of the shift factors used for time鈥搕emperature superposition and the viscosity both follow the same VFT or WLF relationship, and the dynamic fragility at T_g ranges from 117 to 130 for the aromatic ionic liquids investigated, considerably more fragile, in the Angell sense, than the aliphatic analogs. Additionally, an anomalous aging effect in the dynamic viscosity response (i.e., a maximum observed at intermediate frequencies) was found using a strain-controlled rheometer but not using a stress-controlled rheometer.