Effects of Preirradiation Dose and Grafting on the Antithrombogenicity of Polyethylene Radiation-Graft Copolymerized with Acrylamide

To clarify the optimal preparative conditions for the polyethylene (PE) radiation-graft copolymerized with acrylamide (AAm) in terms of the surface antithrombogenicity, the effects of preirradiation dose in air and grafting percentage on the antithrombogenicity were evaluated by implantation of the tubes (3 mm i.d.) into canine peripheral veins. The lowest contact angle of water, 23°, was found at 28% grafting regardless of the dose. The overall antithrombogenicity increased in the order of 1.8 < 5.6 < 3.6< 7.2 MR and showed a peak at about 25% grafting, where contact angle was 26°, independent of dose. The ratios of N_1s/C_1s, obtained from ESCA data at a photoelectron takeoff angle of 15° corresponded well to the trend of their antithrombogenicities. The surface roughness varying with both dose and grafting percentage was considered to enhance the peaks appeared in their ratios. ATR-IR analysis showed the high distribution of graft chains to the surface region for the 3.6 MR-series. The surface porosity peculiar to the 7.2 MR-series was considered to contribute to the antithrombogenicity.