A pH-responsive cyclopolymer having phospho- and sulfopropyl pendents in the same repeating unit: Synthesis, characterization, and its application as an antiscalant

A new zwitterionic monomer 3-[diallyl{3-(diethoxyphosphoryl)propyl}ammonio] propane-1-sulfonate has been synthesized and cyclopolymerized to give the corresponding polyzwitterion (±) (PZ) bearing both phosphonate and sulfonate functionalities on each repeating unit. phosphonate ester hydrolysis in PZ gave a pH-responsive dibasic polyzwitterionic acid (±) (PZA) bearing PO₃H₂ units. The PZA under pH-induced transformation was converted into polyzwitterion/anion (± -) (PZAN) and polyzwitterion/dianion (± =) (PZDAN) having respective PO₃H^- and  PO₃ ^2- units. The polymers′ interesting solubility and viscosity behaviors have been investigated in detail. The apparent protonation constants in salt-free water and 0.1 M NaCl of the PO₃ ^2- in (± =) (PZDAN) and PO₃H^- in (± -) (PZAN) as well as in their corresponding monomeric units have been determined. Evaluation of antiscaling properties of the PZA using supersaturated solution of CaSO ₄ revealed ≈100% scale inhibition efficiency at a meager concentration of 20 ppm for a duration of 45 h at 40 °C. The PZA has the potential to be used effectively as an antiscalant in reverse osmosis plant.