Modeling and control of polymerization processes is a problem of great commercial interest. Comprehensive kinetic models can be used as tools to predict properties of reaction products without the need for elaborate experimentation. In this work, we address the problem of modeling a 4 monomer acrylate - methacrylate - styrene free-radical co-polymerization reaction in semi-batch mode with the objective of converting the mode of operation from batch mode to continuous mode. Estimation of kinetic parameters is key to the development of reliable models. In this work, a mechanistic model for the polymerization reaction was implemented in PREDICI, and further tuning of the model was carried out through parameter estimation. Polymer properties such as molecular weight distribution (MWD) determine utility and stringent control over reactor conditions is critical for manipulating these desirable properties. In order to identify monomer set points, correlation mapping between monomer set points and molecular weight distributions. Further, a predictive model for the continuous mode was implemented and an inventory control scheme was demonstrated to work well for this complex polymerization process.