Phosphonobetaine/sulfur dioxide copolymer by Butler's cyclopolymerization process

A phosphonobetaine/SO2 copolymer polyphosphonobetaine (PPB) has been prepared for the first time using Butler's cyclopolymerization process. The unquenched valency of nitrogens in the zwitterionic units has made the polymers pH-responsive; and as such permitted us to study anionic polyphosphonobetaine (APP) - to - polyzwitterion (PPB) transition by changing the type of dominant charges and their densities in the copolymer backbone. In contrast to many polycarbo- and sulfobetaines, the PPB was found to be soluble in salt-free water as well as in salt (including Ca2+ and Li+)-added solutions. The PPB demonstrated 'antipolyelectrolyte' solution behavior; interestingly it showed higher intrinsic viscosity value in LiCl than in 1.0 N NaI.