Synthesis and application of a cyclopolymer bearing a propylphosphonic acid and a propylcarboxylic acid pendants in the same repeating unit

Diallyl[3-(diethoxyphosphoryl)propyl](3-ethoxycarbonylpropyl)ammonium chloride [ (CH₂CH=CH₂)₂N⁺{(CH₂)₃PO₃Et₂} {(CH₂)₃CO₂Et} Cl⁻], a new diallyl quaternary ammonium salt, has been cyclopolymerized to its cationic polyelectrolyte having pyrrolidine rings embedded in the polymer backbone. The polymer represents the first example of a cyclopolymer in which each repeating unit contains a propylphosphonate as well as a propylcarboxylate pendant. The hydrolysis of one, two or all the three-ester groups in the polymer afforded a series of pH-responsive macromolecules having identical degree of polymerization, which permitted a meaningful comparison of their solution behaviors. Apparent pK_as of the triprotic repeating unit have been determined to be 2.52, 5.32 for 9.02 for the functionalities –PO₃H₂, −CO₂H, and –PO₃H⁻, respectively. The completely hydrolyzed polymer containing PO₃H₂ and CO₂H groups demonstrated remarkable antiscalant behavior; at a concentration of 10 ppm, it inhibited the scaling of CaSO₄ from its supersaturated solution with an inhibition efficiency of 100 % for over 500 min. The polymer may thus be exploited as an antiscalant in reverse osmosis plants.