New levulinic acid-based deep eutectic solvents: Synthesis and physicochemical property determination

Recently, deep eutectic solvents (DESs) have emerged as new and inexpensive ionic liquids (ILs) analogues. They possess attractive and similar solvent properties with traditional ILs. In present work a serials of DESs were prepared by pairing renewable levulinic acid (LA) as hydrogen donor with seven quarternary ammonium salts as hydrogen acceptor. The samples were further characterized in the temperature ranging from 293.15 to 333.15 K at atmospheric pressure with the results of density (0.99891-1.17735 g cm− 3), dynamic viscosity (12.70-376.50 mPa s), electrical conductivity (0.35-8.27 mS cm− 1), and refractive index data (1.44384-1.47273). The temperature dependence of these properties was explored and correlated with simple linear or Vogel-Fulcher-Tamman (VFT) models. The volume expansivities (β), molar volumes (Vm), molar refractions (Rm), and free volumes (fm) values have been calculated on the basis of density and refractive index data. The active energy of viscosity (Eη), molar electric conductivity (Λ), and ionicity were also determined. Partial structure-property relationship for DESs was also investigated. The tunable properties make DESs as a potential reaction medium, electrochemical process medium, solvent and absorbent. Therefore, the determination and correlation can provide relevant information for the engineering and industrial applications of DESs.