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)(2)N+{(CH2)(3)PO3Et2} {(CH2)(3)CO2Et} 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(a)s 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.