# Densities and Viscosities of Ionic Liquid with Organic Solvents
## 3 Results and Discussion
### Effects of Organic Solvents on The Viscosities of IL
Figure 3: The viscosities of binary mixtures for [C\({}_{6}\)mim] [OAc] with solvents as a function of ionic liquid mole fraction. Towards further understanding the effects of organic solvents on the viscosity of IL, the viscosity deviation \(\Delta\eta\) is obtained by:  
\[\Delta\eta=\eta_{m}-\sum x_{i}\eta_{i} \tag{9}\]  
where \(\eta_{\rm m}\) is the viscosity of binary mixture, \(x_{\rm i}\) and \(\eta_{\rm i}\) are the mole fraction and viscosity of pure substance \(i\), respectively. Figure 4 and Figures S16-S18 (in the Supplementary Material) present the viscosity deviations of binary mixtures as a function of IL mole fraction at atmospheric pressure. As shown in the figures, in the studied temperatures and compositions, all the deviations are negative, and the graphs are asymmetric. The absolute values decrease with the increase of temperature, indicating that at low temperature, the viscosities of the binary mixtures are far from those of the ideal mixtures. Moreover, the maximum absolute values are detected at the IL-rich area. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**(1 – \(x\)) Co-Solvent** & \(x\) **IL** & \(\eta_{0}\)**/mPa-s** & **B/K** & \(T_{0}\)**/K** & **AARD/\%** & \(E_{\eta_{1}\)(303.15 K)/kJ\(\cdot\)mol\({}^{-1}\)** \\ \hline DMA & 1.000 & 0.29 & 713.53 & 213.03 & 0.34 & 67.13 \\  & 0.880 & 0.62 & 532.00 & 218.60 & 1.15 & 56.86 \\  & 0.776 & 0.00 & 4731.69 & 30.50 & 0.96 & 48.64 \\  & 0.606 & 0.27 & 553.48 & 200.43 & 0.98 & 40.08 \\  & 0.473 & 0.00 & 1913.12 & 89.26 & 0.44 & 31.95 \\  & 0.366 & 0.27 & 353.04 & 205.97 & 0.93 & 28.57 \\  & 0.278 & 0.08 & 626.69 & 158.80 & 0.47 & 22.98 \\  & 0.204 & 0.10 & 544.50 & 154.29 & 1.39 & 18.77 \\  & 0.064 & 0.31 & 110.03 & 230.29 & 0.52 & 15.84 \\  & 0.000 & 0.06 & 541.64 & 99.64 & 0.10 & 9.99 \\ DMF & 0.860 & 0.01 & 1844.67 & 126.91 & 1.11 & 45.38 \\  & 0.744 & 2.96 & 222.14 & 248.34 & 0.71 & 43.12 \\  & 0.564 & 0.04 & 1001.77 & 166.63 & 1.17 & 41.07 \\  & 0.430 & 0.23 & 568.28 & 187.96 & 0.98 & 32.72 \\  & 0.326 & 0.02 & 1776.25 & 26.16 & 0.68 & 28.22 \\  & 0.244 & 1.13 & 127.29 & 240.03 & 0.75 & 24.42 \\  & 0.177 & 0.78 & 119.72 & 248.63 & 0.98 & 16.95 \\  & 0.054 & 0.62 & 43.92 & 248.21 & 0.40 & 11.12 \\  & 0.000 & 0.12 & 288.97 & 149.77 & 0.25 & 9.39 \\ DMSO & 0.868 & 0.02 & 1412.70 & 163.95 & 0.63 & 55.71 \\  & 0.757 & 0.03 & 1149.61 & 174.13 & 0.80 & 52.77 \\  & 0.580 & 0.04 & 1348.75 & 124.03 & 0.41 & 43.39 \\  & 0.446 & 0.03 & 1163.37 & 144.04 & 0.84 & 35.11 \\  & 0.341 & 0.14 & 586.78 & 183.05 & 1.01 & 31.08 \\  & 0.257 & 0.02 & 1122.56 & 113.98 & 1.31 & 23.97 \\  & 0.187 & 0.00 & 2047.47 & 21.19 & 0.53 & 19.68 \\  & 0.057 & 0.21 & 289.89 & 191.35 & 0.43 & 17.72 \\  & 0.000 & 0.04 & 791.15 & 95.50 & 0.20 & 14.02 \\ \hline \hline \end{tabular}
\end{table} 
Table 13: The parameters for Equation (7), the average absolute relative deviations, and the energy barriers at 303.15 K.  
For the analysis, the solvatochromism is introduced to study the interactions in the binary mixtures using empirical solvent parameters: solvent acidity (\(\alpha\)), solvent basicity (\(\beta\)), normalized empirical polarity (\(E_{T}^{N}\)), and dipolarity/polarizability (\(\pi^{*}\)). These values are \(\alpha=0\), \(\beta=0.76\), \(E_{T}^{N}=0.377\), \(\pi^{*}=0.88\) for DMA, \(\alpha=0\), \(\beta=0.69\), \(E_{T}^{N}=0.386\), \(\pi^{*}=0.88\) for DMF, \(\alpha=0\), \(\beta=0.76\), \(E_{T}^{N}=0.444\), \(\pi^{*}\approx\)1 for DMSO. The parameters for IL anion are \(\alpha=0.43\), \(\beta=1.05\), \(E_{T}^{N}=0.611\), \(\pi^{*}=1.04\)[9]. The parameter of solvent acidity means the ability to be as the hydrogen bond donor and the values are zero, indicating that the solvents lack the ability. The parameters of solvent basicity in the solvents are in the range of 0.69-0.76, showing the ability to perform as the hydrogen bond acceptor.