Oxygen Diffusion in Glassy Polymer Films:  Effects of Other Gases and Changes in Pressure

Sensitized singlet oxygen phosphorescence has been used to quantify oxygen diffusion in polystyrene and poly(methyl methacrylate) films. Prompted by unexplained results from previous studies (Macromolecules 1994, 27, 7041−7048; Can. J. Chem. 1995, 73, 1831−1840), the present experiments have been performed to better characterize the behavior of this photophysical probe of oxygen diffusion under a variety of conditions. Specifically, at total pressures less than 500 Torr, the effects of pressure changes and added nitrogen gas on the measured oxygen diffusion coefficient, singlet oxygen phosphorescence intensity, and rate constant for sensitizer quenching by oxygen have been examined. The results indicate that there is a “low” pressure domain in which the oxygen diffusion coefficient depends both on the oxygen pressure and on the pressure of an added copenetrant. Data obtained are discussed within the context of the dual-mode sorption theory.