Monodisperse polyampholyte latexes that contain 25/23 and 29/18 mol % of polystyrylmethyl(trimethyl)ammonium and methacrylate groups were prepared by emulsion polymerization of vinylbenzyl chloride (VBC), tert-butyl methacrylate (tBMA), styrene, and divinylbenzene followed by stepwise conversion of the VBC and tBMA to cations and anions, respectively. As NaCl is added to aqueous dispersions, the polyampholyte latexes shrink up to 0.5 M and then swell up to 5 M NaCl, in which the particles are colloidally stable. The polyampholyte latexes also are colloidally stable in 1.2 M BaCl2 solution. In contrast, the precursor quaternary ammonium chloride polyelectrolyte latexes coagulate rapidly in NaCl and BaCl2 solutions.
