Cloud point behavior of thermosensitive triblock copolymer L61 in the presence of electrolytes

ABSTRACT

Herein the effect of additives on the cloud point of thermosensitive copolymer Poly (ethylene oxide)–Poly (propylene oxide)–Poly (ethylene oxide) (PEO–PPO–PEO, L61) was investigated, including NaCl, NaOH, NaBr, Na₂CO₃, Na₃PO₄, Na₂SO₄, Na₂HPO₄, ZnSO₄, FeSO₄ and MnSO₄ at different concentrations. It was found that the cloud point of L61 was lowered by adding the electrolytes and decreased linearly with increasing electrolytes concentration. In these systems, the addition of polyvalent anions resulted in a more pronounced salting-out effect than monovalent anions. A depression in the cloud point of L61 in the presence of multivalent electrolytes was observed in a trend of > >Cl⁻. Meanwhile, the ability of divalent anion lower cloud point evaluated by Gibbs free energy was appropriated, and the order as follows: > > . The capacity of divalent cation to reduce the cloud point followed the order Zn²⁺>Fe²⁺>Mn^2+.

GRAPHICAL ABSTRACT

KEYWORDS:

• Cloud point
• electrolytes
• L61
• thermosensitive copolymer