The cloud point and the liquid-liquid equilibrium behaviors of L31∖L61-K2CO3∖C4H4O6K2 aqueous two-phase systems at different temperatures

The cloud point (CP) of triblock copolymer L31 (Mn = 1100 g mol−1) and L61 (Mn = 2100 g mol−1) solutions was determined in the absence and presence of two salting-out salts (K2CO4, C4H4O6K2) at different concentrations. The results show that the addition of K2CO3 and C4H4O6K2 decreases the CP of copolymer solutions and the increase in the molecular weight can also decrease the CP of copolymer solutions. The anions order to decreases the CP of L31 or L61 is as follows: CO32−>C4H4O62−. Meanwhile the liquid-liquid equilibrium (LLE) data for L31/L61-K2CO3/C4H4O6K2 ATPSs was measured at three temperatures (273.15, 278.15 and 283.15) K. An increase in temperature causes an increase in the slope of the tie-line (STL) and the tie line length (TLL). A significant alteration in the biphasic area for the temperature ranging from (273.15–283.15) K is observed. The anions order to induce the phase-separation for systems containing L31 or L61 is as follows: CO32−>C4H4O62−. The two-phase region in the phase diagram also expands with the increase of the molecular weight of copolymer.

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