Polyzwitterion-to-polyampholyte transition using pH-responsive cycloterpolymers of diallyldimethylammonium chloride, (N,N-diallylammonio) methanecarboxylate and sulfur dioxide

The cycloterpolymerizations of varying proportions of diallyldimethylammonium chloride (I) and N,N-Diallyl-N-carboethoxymethylammonium chloride (II) in the presence of sulfur dioxide afforded a series of cationic (+) polyelectrolytes (CPEs) (III) in excellent yields. CPEs, upon acidic hydrolysis of the ester functionalities of the repeating units of II, resulted in the formation of cationic/zwitterionic (+/±) polymers (IV). pH-responsive zwitterionic units of ammonioethanoate (NH ⁺CH ₂CO ₂ ^-) (having unquenched valency of nitrogen) in IV was converted to its anionic counterparts (NCH ₂CO ₂ ^-) by treating with equivalent amount of NaOH to give cationic/anionic i.e., ampholytic (+/-) polymers (V) with a charge symmetry or asymmetry arising out of either excess of cationic or anionic centers. The transformations of III to IV to V have thus provided an opportunity to study the effects of the polyelectrolyte-to-polyzwitterion-to-polyampholyte transitions on the solution properties of these polymers. Basicity constants of the carboxylate group (NH ⁺CH ₂CO ₂ ^-) in IV as well as the amine group (NCH ₂CO ₂ ^-) in V were found to be "apparent" and as such follow the modified Henderson-Hasselbalch equation.