A mathematical model for free-radically initiated semi-continuous emulsion polymerizations of a multimonomer system containing vinylic, divinylic and acidic monomers in the presence of chain transfer agent (CTA) was deleloped. In addition to the more traditional aspects of emulsion polymerization, the model takes into account both the presence of water-soluble monomers and the formation of gel due to the polymerization of a divinylic monomer in the presence of CTA, The outputs of the model are the time evolution of monomers conversions, copolymer composition, molecular weight of the sol polymer and gel fraction.