Annealing and Ultraviolet Treatment of Plasma Fluorocarbon Films for Enhanced Cohesion and Stability

Stents, commonly used for the treatment of cardiovascular diseases, are mainly made of 316L stainless steel. They are, however, prone to corrosion when they are in contact with human body fluid. To prevent this corrosion process and to ameliorate their patencies, in this study, we used a strategy to cover stent materials with a protective fluorocarbon layer deposited by plasma polymerization. In an approach to optimize its cohesion properties and stability, posttreatments, namely, thermal annealing and UV irradiation, were applied on the ultrathin fluorocarbon film. A combination of X-ray photoelectron spectroscopy, polarized near-edge X-ray absorption fine-structure spectroscopy, and time-of-flight secondary ion mass spectrometry demonstrated that UV treatment led to chain scission and film crosslinking and, in this way, decreased the amount and/or size of nanoscaled defects originally present in the films. Annealing on the other hand induced a film reorganization in favor of longer, well-ordered fluorocarbon chains. However, a deformation process that was applied to study the film adhesion properties induced chain scissions with reorganization. Aging tests exhibited an oxidation of the topmost layer for both the as-deposited and posttreated samples. Finally, the film stability was improved after UV treatment for both the nondeformed and deformed samples. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 3176 3186, 2010