Comprehensive experimental results are presented for surfactant-free emulsion polymerization of styrene with water-soluble, ionic initiators. Special emphasis is placed on the particle nucleation, the chemical structure of the nucleating species, the change of latex, particle and polymer properties as well as the development of particle morphology with polymerization time. Under special conditions the appearance in transmission electron microscopy pictures of less electron dense anomalous particles is observed. The formation of these structures is discussed and possible formation mechanisms presented. Dialysis of the latexes changed their properties drastically as they became unstable to coagulation. The original latexes did not change their properties over several months.

Latices were prepared using polymerization systems containing styrene saturated water and potassium peroxodisulfate (buffered with sodium hydrogen carbonate). A high amount of low molecular weight oligomers was detected inside the particles by GPC. MALDI-TOF-MS analysis of the polymer phase show several combinations of sulfate-, hydroxyl-, carboxyl- and hydrogen end groups. The molar ratio of sulfur to oxygen was calculated from elementary analysis data to be between 0.04 to 0.10. These results indicate that the initiation via SO 4 - -radicals is not the exclusive reaction.