Equilibrium Phase Behavior of Triblock Copolymer + Salt + Water Two-Phase Systems at Different Temperatures and pH

Data on phase equilibrium of aqueous two-phase systems formed by mixture of triblock copolymer, potassium phosphate, and water were measured as a function of three temperatures (283.15 K, 298.15 K, and 313.15 K), two pH values (7 and 12), and two copolymer molar masses (L35 of 1900 g mol -1 and F68 of 8400 g mol -1 ). The effect of the temperature was more pronounced on the behavior of the ATPS formed by the L35 copolymer as compared with that induced by the F68 copolymer. Temperature variation affected more intensively the tie line slope than the binodal position. The pH increase shifted the binodal curve to higher copolymer and phosphate concentrations corresponding to a decrease in the region of two-phase coexistence. The effect of the molar masses on the behavior of the phase diagrams for both copolymers was offset by the effects associated with the hydrophobicity of the macromolecules.