ABSTRACT
Since the F/C ratio decreases and the O/C ratio increases after water immersion, the ratio of (F/C ratio of water immersed sample)/(F/C ratio of dry sample) is less than 1, but the ratio of (O/C ratio of water immersed sample)/(O/C ratio of dry sample) is higher than 1. The lower change in the F/C ratio at inner layers (take-off angle > 15 degrees) is due to the net effect of two opposite directions of migration: fluorine-containing moieties located at one layer migrate into deeper layers and fluorine-containing moieties located at the outer layer migrate to this layer. The significance of the ratios (F/C ratio of water immersed sample)/(F/C ratio of dry sample) or (O/C ratio of water immersed sample)/(O/C ratio of dry sample) being near 1.0 is that such a surface of plasma polymers is surface dynamically stable, so that few changes of surface configuration occur after water immersion.
