Investigations on the stability of plasma modified silicone surfaces

The wettability of polymer surfaces and their modification are becoming increasingly important for many applications. In the field of biomaterials, for instance, hydrophilic surfaces are highly desirable as the behavior of a material in a biological environment is primarily determined by its interaction with water. In this work it was investigated the effect of the exposure to different plasmas on the wettability of silicone samples. We have observed that oxygen. argon, and hydrogen glow discharges are quite effective in reducing the water contact angle of such polymer. However, indifferently to efficiency of the treatment, practically all the modified surfaces recovered great part of their original hydrophobicity. We have investigated this hydrophobic recovery using surface energy measurements and theoretical simulations based on the exponential decay of the population of polar groups on the surface. According to our results such recovery can be attributed to the decrease of polar species at the interface water-polymer surface.