Abstract
The effect of the exposure to air or to the substrate during the solvent casting process on the surface chemical composition of Avcothane, a blood compatible biomaterial, was studied by employing Auger electron spectroscopy. The surface layer of 10–15Å thickness was analyzed without sputtering, but for the studies probing a deeper layer, argon ion sputtering at a low enough voltage to prevent artifacts was utilized. It is found that the air facing surface which is the blood contact surface contains a greater amount of silicone polymer and a much lower amount of the urethane hard segment in the first 10–15Å-deep layer than in the comparably thick layer of the substrate surface. However, the depth-composition profile obtained by sputtering indicate that, probably at a deeper depth, the chemical compositions in terms of silicone polymer and hard segment is comparable both in the air side and the substrate side.

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