Effects of irradiation atmosphere on vacuum ultraviolet-induced surface modification of cyclo-olefin polymer substrates

The surface of a cyclo-olefin polymer was modified using vacuum ultraviolet (VUV) light to obtain a wettable surface. We found that the surface hydrophilicity is dependent on both VUV irradiation distance and irradiation time, which affected the concentration of oxygen functional groups. We investigated the effects of the VUV irradiation atmosphere and aging of the treated surfaces. We concluded that VUV treatment in low-humidity air (1% relative humidity) was the most effective condition for introducing oxygen functional groups on the surface; the concentration of these groups decreased over time (a drop of 11% over 5 d).