This study investigates the effects of ethanol mole fraction and temperature on the density and dynamic

viscosity of pseudobinary mixtures containing ethanol and deep eutectic solvents (DESs) composed of

methyltriphenylphosphonium bromide (MTPPB) and ethylene glycol (EG). DESs were prepared with fixed mole ratios of

1:6, 1:8, and 1:10 (MTPPB:EG). The mole fraction of ethanol varied from 0.1998 to 0.9000, and the temperature ranged

from 293.15 K to 323.15 K. Experimental data were correlated using empirical equations to assess the effects of

composition and temperature on the mixtures’ properties. Density and dynamic viscosity measurements demonstrated

that both properties decrease with increasing temperature and ethanol content. Excess molar volume and excess viscosity

calculations revealed negative deviations from ideal solution behavior, indicating strong molecular interactions.

These deviations were attributed to the interstitial effect and hydrogen bonding influenced by the mole fraction of the

components. The study highlights significant differences in molecular packing among the DES1, DES2, and DES3

systems, which were evident in both density and viscosity trends. The findings provide valuable insights into the

design and application of DES-ethanol mixtures in environmentally friendly processes, showcasing their potential in

various industrial applications.

Deep eutectic solvent, Dynamic viscosity, Excess molar volume, Correlation

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