The emulsion copolymerization kinetics of styrene-butyl acrylate was studied in a batch process. The effect of the initiator, emulsifier, chain transfer agent and monomer Concentration on copolymerization rate and molecular weight distribution is discussed. Thermal and viscoelastic properties of copolymers were measured. It was found that the n-dodecylthiol introduced into the reactor with the monomers did not affect the copolymerization rate (no redox reaction with the initiator) but the molecular weight was strongly dependent upon its concentration. These two kinetic parameters increase with increasing the butyl acrylate concentration.Le solvant utilise est du CDC13 avec du tgtra-

Styrene(S)-Methyl methacrylate (MMA) COPO-lymers have been synthesized via batch and semicontinuous processes. The copolymers obtained in both processes were richer in styrene than the initial monomers composition. This fact is strongly influenced by the solubility of MMA in water. The experimental results also showed the existence of an inverse relationship between initiator concentration and molecular weight and consequently in the flow properties of the materials. Furthermore, the molecular Weight and flow properties did not show an important dependence on emulsifier content. It was found that the rate of copolymerization was an inverse function of the electrolyte present in the reaction medium. Comparison between copolymers made via batch and semiamtinwusly pointed out that in general the materials made in a batch process have lower viscosity and elasticity than its semicontinuous counterparts.