In polymer industry, engineers seek to obtain polymers with prescribed end-use properties, high productivities, and low cost. Thus, the optimization of a manufacturing process with all those goals and constraints belongs to a problem domain that aims to achieve the best trade-off possible. This article concerns the optimization of the batch emulsion polymerization of styrene and alpha-methylstyrene. An accurate model was developed to describe the complete patterns of the emulsion polymerization. Key parameters of the model were identified on the basis of batch experimental data. The model was then used to simulate, under several operating conditions, the polymerization rate, the overall conversion of monomers, and the number and weight-average molecular weights. A multicriteria optimization approach based on an evolutionary algorithm and the concept of dominance from the Pareto frontier theory was used. Last, a decision aid system based on the Choquet integral was proposed to determine the optimal operating conditions with the preferences of the decision maker taken into account. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 120: 3421-3434, 2011