Latexes of 100 nm diameter were synthesized by emulsifier-free copolymerization of styrene, sodium styrenesulfonate, and 1-5 wt % divinylbenzene using persulfate initiator at 91-degrees-C. A shot growth method was used to incorporate a high density of sulfonate groups. Coefficients of variation of particle size were 0.04-0.08 without resort to seed growth polymerization. Redox initiation at 40-50-degrees-C produced larger, more polydisperse, and less colloidally stable crosslinked latexes.