The Cloud Point Behavior and Liquid-Liquid Equilibrium of Poly(Ethylene Glycol)-Block-Poly(Propylene Glycol)-Block-Poly(Ethylene Glycol) with Five Salting-Out Salts (K2SO4, K2CO3, KCl, KNO3, KBr) at 283.15 K

摘要

The cloud points (CP) of aqueous solutions of two triblock copolymers, poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol), L31 (M (n) = 1100 g center dot mol(-1)) and L61 (M (n) = 2100 g center dot mol(-1)) were determined in the absence and presence of five salting out salts (K2SO4, K2CO3, KCl, KNO3, KBr) at different concentrations, and the liquid-liquid equilibrium (LLE) data for L31/L61-K2SO4/K2CO3/KCl/KNO3/KBr ATPSs were measured at 283.15 K. The results show that the addition of these salts decreases the CP of aqueous copolymer solutions and the copolymer with the higher molecular weight has a lower CP. The order in which salts depress the CP is as follows: . When the concentration of salt is the same, the anion order to depress the CP is as follows: , . The abilities of the salt and anion to induce phase separations are in accord with their ability to reduce the CP. The results also show that the copolymer with the higher molecular weight phase separates more easily.