Angle-resolved XPS study of the effect of x-radiation on the aging of polystyrene exposed to an oxygen/argon plasma

Polystyrene films spin-coated onto glass were exposed to an oxygen/argon plasma. The depth profile of the oxygen in the polystyrene surface was characterized by angle-resolved x-ray photoelectron spectroscopy (ARXPS) 2,24 and 92 h following the plasma treatment. It was found that oxygen was lost from the surface over time, mainly from C=O and especially O-CO-O groups, and that the exposure to x-rays during the ARXPS measurement accelerated this loss. At the 92 h mark, a linear, negative correlation was found between the oxygen content of the polystyrene surface and the water contact angle. The relative merits of the three models used to interpret the ARXPS data are discussed. Copyright (C) 2002 John Wiley Sons, Ltd.