Coexistence Curves of Aqueous Two-Phase Systems of Some pH-Responsive Homo- and Copolymers of 3-(Diallylammonio)propane-1-sulfonate and Urethanized Poly(ethenol) or Poly(oxyethylene)

Poly(ethenol) (PE) was partly urethanized with urea to obtain urethanized PE (UPE) having a urethanated mole fraction of 0.13. A series of pH-responsive polysulfobetaines: homopolymer poly[3-(diallylammonio)propane-1-sulfonate], copolymer poly[3-(diallylammonio)propane-1-sulfonate-alt-sulfur dioxide], and terpolymer poly[3-(diallylammonio)propane-1-sulfonate-alt-sulfur dioxide-ran-diallyldimethylammonium chloride-alt-sulfur dioxide], was prepared via cyclopolymerization process involving pH-responsive zwitterionic (+/-) 3-(diallylammonio)propane-1-sulfonate, cationic diallyldimethylammonium chloride and sulfur dioxide. The composition and phase diagram of aqueous two-phase systems (ATPSs) consisting of UPE or poly(oxyethylene) (POE) and the synthesized polysulfobetaines as polymer components were studied in some details using H-1 NMR spectroscopy. The presence of trivalent nitrogen and negatively charged oxygen in each repeating units of the polymers permitted the change of the charge types in the polymer chain to zwitterionic/anionic (+/- -), zwitterionic/cationic (+/- +), ampholytic (+ -), or anionic (-). The effects of charge types and their densities, and ionic strength on the phase diagrams were investigated. The phase separation happened at a relatively low total polymer mass fraction of below 0.10. The solubility dependence of the polyzwitterions on variable pH make them suitable candidates for potential industrial applications in bioseparations since at lower pH, the polymer in the zwitterionic form can be precipitated out and recycled.