TY - JOUR
T1 - Rheology of Imidazolium-Based Ionic Liquids with Aromatic Functionality
AU - Tao, Ran
AU - Simon, Sindee L.
N1 - Publisher Copyright:
© 2015 American Chemical Society.
PY - 2015/7/31
Y1 - 2015/7/31
N2 - 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-temperature superposition and the viscosity both follow the same VFT or WLF relationship, and the dynamic fragility at Tg 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.
AB - 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-temperature superposition and the viscosity both follow the same VFT or WLF relationship, and the dynamic fragility at Tg 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.
UR - http://www.scopus.com/inward/record.url?scp=84940845729&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcb.5b06163
DO - 10.1021/acs.jpcb.5b06163
M3 - Article
AN - SCOPUS:84940845729
SN - 1520-6106
VL - 119
SP - 11953
EP - 11959
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 35
ER -