Alternate cyclopolymer of diallylglutamic acid and sulfur dioxide

The monomer N,N-diallylglutamic acid hydrochloride [(CH₂CH-CH₂)₂NH⁺CH(CO₂H)CH₂CH₂CO₂H·Cl^-] (I)/SO₂, underwent cyclopolymerization to afford the alternate cationic polyelectrolyte (CPE) poly(I-alt-SO₂) (II) in very good yields. Upon depletion of HCl during soaking in water, water-soluble triprotic (+) II was transformed to water-insoluble diprotic zwitterionic (±) III containing residues of glutamic acid in each repeating unit. Upon treatment with 1 and 2 equivalents of NaOH, polyzwitterions (±) III, was converted into water-soluble monoprotic poly(zwitterion-anion) (±-) IV and the fully deprotonated polydianion (=) V, respectively. Basicity strengths of the chelation centers of CO₂^- and nitrogen in (=) V have been determined. The polymer demonstrated its effectiveness as an antiscalant in the inhibition of CaSO₄ scaling. Keeping in view the pH-dependent solubility of the polymers, a recyclable aqueous two-phase system (ATPS) comprising of (=) V and polyethylene glycol has been constructed for the potential purification of biomolecules. After its use, the ATPS can be recycled by precipitating the ionic polymer in the form of (±) III at a lower pH.