In this work, a viscosity model for choline chloride-based deep eutectic solvents (DESs) was developed. In addition to temperature, the new model presented here considers the composition of the salt in the DES, which was not the case for all previously reported viscosity models. Two forms of the proposed model were optimized and fitted to viscosity experimental data. The developed model was tested using the experimental viscosity values for nine common choline chloride-based DES systems of different hydrogen bond donors. The performance of the model was evaluated using three different statistical indicators, namely average relative deviation, correlation coefficient (R2) and standard deviation. In addition, a significance t-test was also conducted on each of the fitted DES viscosity data. The statistical indicators showed a very good agreement between the model-predicted viscosity and the experimental viscosity values for the DESs with relatively low viscosities (DES1, DES2, DES4 and DES5). For DESs with high viscosities (DES3, DES7, DES8 and DES9), the second model gave better predictions. Overall, this proposed model was capable of predicting DES viscosities for different salt compositions at different temperatures as supported by the statistical significance t-test and other statistical indicators.
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