Evaluation of solute-solvent interaction and phase separation for aqueous polymers solutions containing choline chloride/D-sucrose natural deep eutectic solvent through vapor-liquid equilibria, volumetric and acoustic studies

In polymer-based aqueous biphasic systems (ABSs), the understanding the role of different types of polymers in phase separation is important in the selection of a suitable ABS used for separation of biomaterials. For this purpose, in this work, a systematic investigation of ternary aqueous solutions containing one deep eutectic solvent (NADES) obtained from mixtures of choline chloride as HBA and D-sucrose as HBD, and different water soluble polymers polyethylene glycol 400 (PEG(400)), polypropylene glycol 400 (PPG(400)), and polyethylene glycol dimethyl ether 250 (PEGDME(250)) at a molar ratio of 1:1 was made by the volumetric, ultrasonic, and vapor-liquid equilibria (VLE) studies at T = 298.15 K. The obtained water iso-activity lines showed that the system containing PPG(400) and NADES has negative deviation from the semi-ideal solution and therefore solute-solvent interactions are unfavorable suggesting the occurrence of phase separation in this system. But in the case of PEG(400) and PEGDME(250) these deviations are positive and there are favorable interactions between the polymers and NADES which means that phase separation in these systems is unlikely. The obtained values from the density and acoustic studies were used for calculating the limiting values for apparent molar volume (V-phi(0)), apparent molar isentropic compressibility (k(phi)(0)), the transfer molar volume (Delta V-tr(phi)0), and also isentropic compressibility (Delta(tr)k(phi)(0)) of polymers from water to aqueous NADES solutions. These results are consistent with the results of water activity measurements in regard to the solute-solvent interactions and phase separation in the studied ternary systems. (C) 2019 Elsevier Ltd.