PARTICLE-SIZE DISTRIBUTION AND MOLECULAR-SIZE DISTRIBUTION OF POLYMERS IN SOAP-FREE EMULSION POLYMERIZATION OF STYRENE

Polystrene (PS) particles, generated from soap-free emulsion polymerization of styrene monomer, water, and potassium persulfate, were investigated by photon correlation spectroscopy (PCS) and TEM. The particle size distribution (PSD) was quite uniform. From the data of PCS, it could be said that lots of particles flocculated in the final stage of reaction. It was also deduced from the molecular weight distribution (MWD), measured by GPC, that, during the early stage of reaction, molecules with low molecular weight (< 4000) might exist and the particles were perhaps formed through micellar-type nucleation mechanism. When initiator concentration increased, reaction rate increased but weight average molecular weight, tensile modulus, and elongation decreased. The number density of particles was found to be proportional to 0.49 power of initiator concentration. However, monomer concentration did not seem to have any great effect on all of them above.