Abstract: An implantable prosthesis comprises a hydrogel enclosed within a flexible envelope. The hydrogel contains both hydrophilic and hydrophobic domains. It is prepared by copolymerizing a hydrophilic monomer such as water soluble N-vinylpyrrolidone, acrylates or methacrylates with non-water soluble monomers such as acrylates, methacrylates, N-vinyl carbazole, its derivatives, or a non-water soluble derivative of N-vinylpyrrolidone. The flexible envelope may be either porous or non-porous. The hydrogel may be either solid or composed of particles of a size greater than the porosity of the envelope.

Abstract: A process for grafting a hydrophilic polymer of a carboxylic acid or a salt thereof onto the surface of a natural rubber article by contacting said article in reaction inert solvent with a vinyl carboxylic acid anhydride and initiator, and subsequent washing and hydrolysis of anhydride groups to carboxylate groups and an article when prepared by the invention process.