AbstractThe vapor‐phase radiation graft polymerization of styrene, methyl methacrylate, and acrylonitrile on surface of dispersed filler (magnesium oxide) was studied. It was established that the polymer graft films are irreversibly chemically bound to the surface, cover it with a discontinuous layer which leaves a part of the surface free from polymer in the form of a mosaic. The grafting modifies the surface and increases the compatibility of filler with the polymer medium.