We employed an ozone-induced grafting process to prepare membrane-hydrogel hybrid biomaterials. Exposure of isotactic polypropylene to ozone resulted in surface oxidation, as detected by ESCA, and the formation of peroxides and hydroperoxides. The amount of oxygen-bearing moieties, as detected by FT-IR, was increased when a microporous membrane with a large surface area was used. Ozonation for an extended period of time, 1-2 h, resulted in a degradation of microporous PP, observed with SEM as an enlargement of pores and brittle characteristics of the material. The molecular weight of PP was dramatically reduced after as little as 5 min of ozonation. Exposure to ozone for longer periods of time contributed to further reductions of the molecular weight and gradual modification of chemical composition of polypropylene, restricted, however, to the surface or intercrystalline amorphous regions. It was possible to graft 2-hydroxyethylemthacrylate (HEMA) to the ozonated samples, such that the graft copolymer acted as continiuous matrix consequently linked to and reinforced by the PP crystals.