Experimental and simulation-based sensitivity studies on the process of evolution of particle size distribution (PSD) in semibatch emulsion polymerization are presented. The experimental studies identify an effective control strategy for PSD, and the appropriate manipulated variables. The complementary simulation studies identify the potentially reachable PSDs in the complex operating space. The study also examines the effect of uncertainties and disturbances on the reachable distributions, to evaluate the benefits of in-batch feedback control.