Salt-dependent phase behavior of aqueous dextran sulfate/polyethylene glycol mixtures

Abstract

Aqueous two-phase systems of neutral polymers with polyelectrolytes were investigated. Aqueous solutions of dextran sulfate (DS) and polyethylene glycol (PEG) were found to phase separate at sufficiently high concentrations. The critical point of phase separation was observed to depend on the salt concentration, as was expected from theory. Construction of phase diagrams of the system at different NaCl concentrations was attempted with polarimetry and density measurements to determine DS and PEG concentrations respectively. While the DS concentrations obtained by polarimetry are reliable, PEG determination by density measurements proved to be problematic due to a high sensitivity to random and systematic error.