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, 7041-70 48; Can. J. Chem. 1995, 73, 1831-1840), the present experiments have been p erformed to better characterize the behavior of this photophysical probe of oxygen diffusion under a variety of conditions. Specifically, at total pre ssures less than 500 Torr, the effects of pressure changes and added nitrog en gas on the measured oxygen diffusion coefficient, singlet oxygen phospho rescence intensity, and rate constant for sensitizer quenching by oxygen ha ve been examined. The results indicate that there is a "low" pressure domai n in which the oxygen diffusion coefficient depends both on the oxygen pres sure and on the pressure of an added copenetrant. Data obtained are discuss ed within the context of the dual-mode sorption theory.