Deep eutectic solvents composed of tetrabutylammonium bromide and PEG: Density, speed of sound and viscosity as a function of temperature

Deep eutectic solvent (DES) is the latest entry in the spectrum of eco-friendly solvents. They are analogues of ionic liquid (IL) with similar physicochemical properties. The accurate value of physicochemical and transport properties at various temperatures are paramount information required for the utilization of DES in industry. In this context, the densities (rho), speeds of sound (u) and viscosities (eta) of tetrabutylammonium bromide based DESs at atmospheric pressure and temperature ranges from 298.15 K to 343.15 K are reported here. The studied DESs were prepared by complexing tetrabutylammonium bromide (HBA) and polyethylene glycol (HBD) of different molar mass (200, 400 and 600). The thermal expansion coefficient alpha(rho), isentropic compressibility kappa(s), intermolecular free length L-f and activation energy for viscosity E-eta have been derived from the measured value of rho, u and eta, respectively. The measured properties of DESs are greatly influenced by temperature, mole ratio of HBA: HBD, molar mass of PEG and strength of H-bonding between HBA and HBD. The experimental value of rho, u and eta for DESs decrease with increase in temperature whereas increase with increase in molar mass of PEG from 200 to 600. However very small change was observed in studied properties when mole ratio of PEG was increased. The eta of DESs steeply decreases between 298.15 K and 323.15 K. The measured and derived properties of DESs will be used to calculate various process parameters for applications of DESs. (C) 2019 Elsevier Ltd.