An aqueous reversible-deactivation radical polymerization (RDRP) approach is used to synthesize sodium polystyrene sulfonate directly from functionalized monomers to give uniformly and completely sulfonated materials. Reproducible gram scale syntheses are achieved under simple one pot reaction conditions at ambient temperatures, and full monomer conversions are achieved within approximately 3 h. Reaction variables such as pH, sodium chloride concentration, and methanol cosolvent have a significant effect on the molecular weights (M-n approximate to 20,000-400,000 g.mol(-1)) obtained by gel permeation chromatography coupled multiangle light scattering. Observed dispersities were reasonably narrow: D approximate to 1.05-1.3. A parametric optimization, rather than direct variation of the monomer to initiator ratio, resulted in some of the highest molecular weight polymers by an RDRP approach. Linear progression between M-n and monomer conversion occurs at a neutral reaction pH, which results in narrow polymer molecular weight distributions, along with high end-group fidelity as demonstrated with chain extension reactions. (c) 2019 Wiley Periodicals, Inc.