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+CH2CO?2-) (having unquenched valency of nitrogen) in IV was converted to its anionic counterparts (NCH2CO?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+CH2CO?2-) in IV as well as the amine group (NCH2CO?2-) in V were found to be apparent and as such follow the modified HendersonHasselbalch equation. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012