Polymer composites based on an epoxy resin oligomer, an amine terminated oligomer or maleic anhydride, and one or several monomers among styrene, methyl methacrylate, butyl methacrylate, glycidyl methacrylate, and acrylonitrile have been prepared using the concentrated emulsion pathway. Each of the components of the composite was first transformed in a concentrated emulsion in which water with a low volume fraction was the continuous phase. The concentrated emulsions containing monomers were partially polymerized (to ensure their stability during the subsequent heating) before being mixed with one or two concentrated emulsions, each containing one of the above mentioned oligomers. The mixture of concentrated emulsions was subjected to heating for the complete polymerization of the monomer and for the reaction between the epoxy resin and the amine terminated oligomer or the maleic anhydride to occur. The reaction generates a crosslinking among the cells of the concentrated emulsions (heterogeneous crosslinking) and thus achieves compatibilization among various incompatible components. The composites were characterized using Fourier transform infra-red spectroscopy, differential scanning calorimetry, swelling, as well as solubility measurements. Tensile measurements showed that the components of the composites were compatibilized and that the latter possess excellent mechanical properties.