Polymer composites based on vinylidene chloride/methyl methacrylate (VDC/MMA) copolymer crosslinked with vinyl-terminated polycaprolactone (VTPCL) were prepared via a concentrated emulsion polymerization procedure. In that method, a partially polymerized solution of VDC, MMA and VTPCL in toluene, containing also an initiator, is dispersed at room temperature in a small amount of an aqueous solution of a surfactant. The concentrated emulsion thus generated is subjected to polymerization at 60 degrees C. Compared to the polymerization in solution, which leads to a swollen bulk material, the concentrated emulsion polymerization provides latexes. The effects of the various constituents on the mechanical properties of the composites were studied via tensile testing. One concludes that there is mutual toughening between PVDC and PMMA, and that additional toughening is produced by the VTPCL. There is an optimum amount of VTPCL and an optimum weight ratio of VDC/MMA for which the toughness is maximum. Composites have also been prepared in which ethyl methacrylate or acrylonitrile replaced partially or completely MMA.