Synthesis and characterization of new cyno-group functionalized ionic liquids and their rheological properties

A series of cyno-group functionalized ionic liquids were synthesized and characterized by ¹H NMR and elemental analysis. The density, melting point and solubility of the ionic liquids were affected by the length of substituted group and the chemical structures of anions. The rheological properties of the ionic liquids under steady, transient and dynamic state were studied with a rheometer over a wide range of temperature and frequencies. It was found that the ionic liquids studied could be considered as Newtonian fluids. Arrhenius equation was employed to describe the relationship between the viscosity and the temperature. The viscous flow activation energy of the ionic liquids calculated was changed regularly with the length change of alkyl substituent. Under transient state condition, the shear stress and viscosity of the ionic liquid l-butyl-3-(β-propanenitrile) imidazolium hexafluorophosphate, as an example, kept constant with the change of time while the shear speed was fixed. However, a decreasing trend was observed when the temperature was increased. The dynamic rheological properties of this ionic liquid were also studied. The complex viscosity and loss modulus were also decreased with increasing temperature.