Structured-particle latexes are prepared from nonionic or slightly cationic latexes, either preformed or polymerized in situ, by emulsion polymerizing monomeric materials which include an ethylenically unsaturated, activated-halogen monomer such as vinylbenzyl chloride in the absence of a sufficient amount of a surfactant to initiate new particles whereby the activated-halogen monomer is copolymerized on the surface of the existing particles which are dispersed in an aqueous media. The resulting structured-particle latex may then be reacted with a nucleophile such as dimethyl sulfide or trimethyl amine to form a latex having stabilizing "onium" groups such as sulfonium groups or quaternary ammonium groups chemically bound at or near the surface of the polymer particles which are dispersed in aqueous media. The cationic latexes are suitable for coatings and organic pigments.