In this thesis, salting-out principle was used to produce new types of aqueous biphasic systems (ABS) consisting of deep eutectic solvent-polymer, tetra alkyl ammonium bromide–electrolyte and tetra alkyl ammonium bromide–polymer. In the first part of this work, phase behavior including vapor-liquid and liquid-liquid equilibria of aqueous solutions of three deep eutectic solvents (DES), prepared by mixing of choline chloride as hydrogen bond acceptor (HBA), and urea, ethylene glycol and glycerol as hydrogen bond donor (HBD) at a molar ratio of 1:2 (ChCl:2HBD), reline, ethaline and glyceline have been investigated in the absence and presence of water soluble polymers polypropylene glycol400 (PPG400), polyethylene glycol400 (PEG400) and polyethylene glycol10000 (PEG10000) at different temperatures. The results show that {PEG + DES} aqueous systems are not capable of inducing phase separation, whereas PPG–DES aqueous systems form ABS above critical concentrations (salting-out effect). It is evident that, the ABS formation seems to be controlled by the competition between the preferential hydration and hydrogen bonding interaction depends on structure of polymer and DES. The liquid–liquid equilibria results for {DES + PPG + water} systems show that the capability of DES for soluting-out of PPG in aqueous solutions follows order glyceline > ethaline > reline. In order to gain further insight regarding the DES properties which govern the preferential hydration in {DES + PPG + water} solutions, the ability of each DES component (HBA and HBD) to form aqueous biphasic systems with PPG was also evaluated. The results revealed that choline chloride as HBA and only glycerol as HBD could solute-out of PPG and undergo phase separation in the aqueous solutions. Finally, the effect of temperature and structure of polymer and DES on the equal water activity lines and binodal curve of the investigated systems has been studied. In addition, in this study, the density and sound velocity
