Reaction kinetics in semibatch emulsion polymerization of methyl methacrylate, were monitored by automatic continuous online monitoring of polymerization reactions (ACOMP) Semibatch reagent feed to the reactor at different flow rates allowed the transition between the monomer starved and flooded regimes and the approach to and maintenance of neat steady state conditions to be monitored and quantified, and yielded relationships between flow regimes and monomer conversion kinetics, polymer weight-average Molecular weight M-w, and intrinsic viscosity [eta](n)., Polymer molecular weight distributions together with late, particle size and number play an important role in defining the macroscopic characteristics and performance of polymeric materials The change in the monomer feed rates during reaction allowed simultaneous Influence oil and verification of the evolution of these parameters during synthesis When flow rate changes to the reactor were made it was verified that the characteristic rate of achieving the new pseudosteady state was close to the first order reaction rate. Multidetector size exclusion chromatography was used to cross-check results and measure Rill distributions of endproducts Latex polymer size was measured with dynamic light scattering An important advance for this fields is that polymer M-w is determined continuously during the reaction and in an absolute fashion, based on multiangle light scattering detection available.