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High performance coatings tailored to medical devices represent a recognised approach to modulate surface properties. Plasma-deposited fluorocarbon films have been proposed as a potential stent coating. Previous studies have shown promising adhesion properties: the 35 nm-thick film sustained plastic deformation up to 25% such as induced during the clinical implantation. In this study, the compositional and morphological changes of plasma-deposited fluorocarbon films were examined during ageing in a pseudo-physiological medium, a phosphate buffer solution (PBS), by angle-resolved XPS, FT-IR data and AFM images. The evolution of the ageing process is discussed: defluorination and crosslinking yielded an oxidized protective top layer onto the films, which showed further degradation.

The interfacial interactions between rigid polyurethane foam (RPUF) and aluminium have been studied to understand adhesion mechanisms. Three different blowing

Polymeric methylene diphenyl diisocyanate (PMDI) is the major component of polyurethane formulations and as a result the adhesion, or indeed abhesion, of polyurethanes, in a variety of forms (foams, coatings and adhesives), to metal substrates will be a function of the interactions between PMDI and metal surfaces. In this paper the adsorption of PMDI on oxidised metal (aluminium and iron) substrates has been investigated. The thermodynamics of adsorption has been examined by the construction of adsorption isotherms derived from ToF-SIMS data. At low solution concentration, the adsorption isotherns of PMDI are not of the Langmuir type, but are shown to conform to Langmuir adsorption at higher solution concentrations (> 1 g L -1 ). The interaction between the PMDI and iron is probably an acidbase interaction, and thus the adsorption of small PMDI molecules is displaced by larger PMDI molecules on the iron surface above a critical solution concentration. By contrast, such displacement is small on the aluminium surface as a result of dominance of covalent bond formation between PMDI and the metal substrate.

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.