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 2 CO   2 − ) (having unquenched valency of nitrogen) in IV was converted to its anionic counterparts (NCH 2 CO   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 2 CO   2 − ) in IV as well as the amine group (NCH 2 CO   2 − ) in V were found to be “apparent” and as such follow the modified Henderson–Hasselbalch equation. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012