Enhancement of the adhesive strength of antithrombogenic and hemocompatible a-C:H:SiO_x films to polypropylene

Silicon- and oxygen-incorporated hydrogenated amorphous carbon films (a-C:H:SiO_x) are deposited onto polypropylene substrates using plasma-assisted chemical vapor deposition to increase their antithrombogenicity and hemocompatibility. To increase the a-C:H:SiO_x film adhesion to the polymer substrate, the latter is pretreated with argon or oxygen ions from the ion source with closed electron drift. The optimum conditions for the ion-beam treatment are determined by measurements of the surface wettability and chemical composition, the film morphology and adhesion. The adhesive properties are evaluated by the pull-off adhesion test. X-ray photoelectron spectroscopy shows the formation of new oxygen-containing functional groups after the exposure to both argon and oxygen ion beams. The highest film adhesion is observed for the substrate irradiated by oxygen ions, when the pull-off force increases from 3.4 to 24 kg/cm². Various characterization techniques such as Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy are employed to study the a-C:H:SiO_x film structure on a polymer substrate. In vitro investigation of platelet adhesion and cytotoxicity helps to evaluate the blood compatibility with the film. The a-C:H:SiO_x film shows low thrombogenicity and no cytotoxic activity towards human leukocytes.