Combined plasma and gamma radiation polymerization method for modifying surfaces

A method for modifying a surface of a hydrophobic material by a gamma-irradiation or electron beam irradiation induced polymerization thereon of one or a mixture of ethylenically unsaturated monomers so as to form a hydrophilic polymeric coating on said surface, the improvement comprising the steps of:

• a) exposing said surface to a glow discharge plasma (GDP) having a power from about 1 to about 500 W and for a time sufficient to induce grafting sites on said surface for the surface graft polymerization of steps b and c;
• b) exposing said surface to a solution of an ethylenically unsaturated monomer or mixture thereof capable, via said ethylenic unsaturation, of gamma-irradiation or electron beam induced polymerization;
• and
• c) irradiating said activated surface with gamma or electron beam radiation in the presence of said ethylenic unsaturated monomer or mixture thereof to thereby form a hydrophilic polymeric surface coating on said surface, said polymerization being initiated by said gamma or electron beam radiation wherein said polymerization is conducted under the following conditions:
• i) monomer concentration in said solution in the range of from about 0.1% to about 50%, by weight;
• ii) total gamma or electron beam dose in the range of from about 0.001 to less than about 0.50 Mrad;
• and
• iii) gamma dose rate in the range of from about 10 to about 2500 rads/min, or electron beam dose rate in the range of from about 10 to about 10.sup.8 rads/min.