Construction of aqueous two-phase systems of the cyclopolymer of (diallylamino)propylphosphonate and its sulfur dioxide copolymer with polyoxyethylene using ¹H NMR spectroscopy

A pH-responsive polyzwitterionic acid [PZA)], poly[3-(N,N-diallylammonio)propanephosphonic acid], and an alternate copolymer PZA·SO₂, poly[3-(N,N-diallylammonio)-propanephosphonic acid-alt-SO₂] have been prepared via cypolymerization. Aqueous two phase systems (ATPSs) of polyoxyethylene (POE)-(NaOH-treated PZA or PZA·SO₂)-water (NaCl) have been investigated. To construct the tie lines, the compositions of the phases were determined by ¹H NMR spectroscopy.The addition of 1, 1.5, and 2 equiv NaOH transform the (±) zwitterionic polymers to their corresponding (±-) zwitterionic-anionic, (±-)/(=) zwitterionic-anionic/ dianionic, and (=) dianionic polyelectrolyte.The influence of NaOH and salt (NaCl) on the binodals have been examined. Increasing the amount of added NaOH pushes the binodals toward lower concentrations, thereby requiring a lesser amount of polymers for phase separation.The NH⁺ and the OH functional groups in (±) PZA and (±) PZASO₂ provide the required motifs for the base-induced change of the charge densities in the macromolecule, whose size and shape can thus be manipulated to facilitate potential separation of proteins in the ATPSs. A combined total mass fraction of less than 0.10 for the component polymers makes these ATPSs viable for industrial applications.The water-insolubility of PZA·SO₂ at lower pH values makes it a suitable component for recycling ATPS.