Chemical States of Plasma Polypyrrole Coatings on Stainless Steel Stents

Polypyrrole synthesized and doped with iodine by plasma was used to cover stainless steel stents in order to reduce the contact of blood with the metallic surfaces in the circulatory system. This study was directed to identify the chemical states in the first 95nm depth of the polymeric coatings using XPS with Ar erosion. The results showed that the coatings have percentages of chemical states of pyrrole that did and others that did not participate in the polymerization. Oxidation was found along the depth profile of the coatings and not only on the surface, which suggests atmospheric oxidation and the formation of oxygen bridges due to the sensitization step applied previously to the polymerization, that could improve the adhesion with the metallic surfaces. The interaction of iodine with the polymer was also identified in the polymers. In general, the coatings have functional groups that are typically found in compatible polypyrroles.