Polystyrene/silica (PS/SiO2) and poly(styrene-co-methyl methacrylate)/SiO2 composite later particles were prepared by surfactant-free emulsion polymerization in the presence of a poly(ethylene glycol) monomethylether methacrylate (PEGMA) macromonomer. The resulting composite particles were stabilized by the negatively charged silica particles that adhered to the surface of the latex particles. Different process parameters were investigated in order to optimize the latex stability and maximize the reaction rate. Mixing in such a surfactant-free process is of major importance and is mainly determined by the type of impeller used (luring the emulsification. The concentrations of PEGMA and silica particles were also optimized in order to improve the interaction between the organic and inorganic phases and ensure a good latex stability. The presence of silica particles on the polymer particle surface was found to affect radical absorption anti decrease therefore the reaction rate.