In Vivo Antithrombogenicity of Poly(tetrafiuoroethylene) Radiation-Graft Copolymerized with Acrylamide

In order to prepare an antitbrombogenic material by making polymer surfaces hydrophilic, acrylamide (AAm) was radiation-graft copolymerized onto poly(tetrafluoroetbylene) (PTPE) tubes by preirradiation in Ar and the following treatment with a monomer aqueous solution. The grafting percentage determined from the weight increment was so small (below 0.3%) that the surface grafting percentage was calculated by ESCA for the grafted tubes. The in vivo antithrombogenicity was evaluated by relative patent time in the implantation into canine peripheral veins and its relation to the contact angle of water or surface grafting percentage was discussed. From the results of ESCA measured at the photoelctron takeoff angles of 15° and 90°, the graft copolymerization was suggested to proceed into a deep layer from a surface thin layer (below 2nm) with low grafting. A grafting of 150% from 15°-measurement (the sampling depth of ca. 2nm) or 500% from 90°-measurement (the sampling depth of ca. 8 nm) was found to result in an antithrombogenic surface superior to the original one and also the grafted surface with the lowest contact angle of 26°.