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This article reports an experimental investigation of free radical miniemulsion copolymerization of styrene (St) and methyl methacrylate (MMA) . Miniemulsion polymerization involves the use of an effective surfactant/cosurfactant system to produce very small monomer droplets. One of the most important parameters in miniemulsion polymerization is the surfactant. The main role of the surfactant is to stabilize the monomer droplets in an emulsion form, to decrease the surface tension in the reaction medium and to stabilize the formed latex particles. If the monomer droplet size can be reduced below 0.5μm, the reduction in the droplet size will result in huge increase in interfacial area. This increased interface will require a monolayer of surfactant to remain stable. The surfactant necessary to support this large interfacial area will come from the break of surfactant micelles. In the present study the effect of cationic surfactant [cetyltrimethylammonium bromide (CTAB) ]and anionic surfactant [sodium dodecyl sulfate (SDS) ] on the colloidal stability of the poly [styrene/methyl methacrylate, P (ST/MMA) ] in the presence of the cosurfactant hexadecane (HD) were experimentally examined. In addition the effect of temperature on monomer conversion and particle stability was also investigated. The overall monomer conversion%, Particle Size and Particle Size Distribution (PSD) were determined employing gravimetry, laser diffraction, respectively. In addition, the particle morphology was observed by scanning electron microscopy (SEM). From experimental investigations it is apparent that overall monomer conversion increases as the polymerization temperature increases, while it does not have a systematic effect on both particle size distribution and average particle size. It was found that both surfactants (SDS, CTAB) concentrations played a critical role in controlling the particle size and subsequently the conversion. Accordingly Comparing the surfactants SDS and CTAB, it was found that under low concentration of each of them, the particles were aggregated, but the phenomenon was not so intense in the case of SDS.
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