A new class of ionic copolymers containing amine and phosphonate functionalities has been prepared for the first time. N,N-Diallyl-3-(Diethylphosphonato)-methylammonium chloride underwent cyclocopolymerization with SO2 to give a cationic polyelectrolyte (CPE) in very good yields. Likewise, ethyl 3-(N,N-diallylammonio)methanephosphonate/SO2 cyclopolymerization afforded the corresponding polyzwitterion-ester (PZE), which on neutralization with NaOH gave the anionic polyelectrolyte (APE). Both CPE and PZE on hydrolysis of the phosphonate ester functionalities gave the same polyzwitterionic acid (PZA). The pH-responsive PZA on treatment with excess NaOH was converted to dianionic polyelectrolyte (DAPE) which on treatment with 1 equivalent HCl afforded the zwitterionic-anionic polyelectrolyte (ZAPE). Solution properties of the CPE, PZE, DAPE, APE and ZAPE having similar degree of polymerization have been studied in some detail. The apparent basicity constants of the amine group in APE have been determined. An aqueous two-phase system of polyethylene glycol-DAPE-H2O (0.4 N NaCl) has been constructed for its potential application in selective separation of toxic metal ions since polyphosphonates are expected to be effective chelators. (c) 2012 Elsevier Ltd. All rights reserved.