Surfactant-free high solids waterborne polymer dispersions were produced under industrial-like semicontinuous conditions by substituting traditional emulsifiers with stabilizing moieties in situ production from a pH and temperature insensitive ionic monomer (sodium styrene sulfonate, NaSS). Copolymerization between NaSS and comonomers occurred through a mechanism that involves solution polymerization in the aqueous phase and compartmentalized polymerization in a shell created around the particles. This knowledge allowed the development of a polymerization strategy that led to high incorporation of NaSS (up to 83.5%). Solids contents over 60 wt% were achieved with modest concentrations of NaSS (1.35 wt%) and a variety of monomers (acrylates, methacrylates, styrene) can be efficiently polymerized. These latexes presented superior salt and freeze-thaw stability without compromising the water sensitivity of the films.