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A recently developed spectroscopic technique was used to determine oxygen diffusion coefficients, D, as a function of temperature in polystyrene and polycarbonate films. The data were quantified by using an Arrhenius expression with the following variables: (a) a diffusion activation barrier, Eact, and (b) a diffusion coefficient, D0, that represents the condition of "barrier-free" gas transport. From the perspective that diffusion depends on free volume, the parameters £act and Do are interpreted to reflect dynamic and static elements of free volume in the polymer matrix. The addition of low molecular weight solutes to these amorphous glasses can alter the oxygen diffusion coefficient by affecting the dynamic and/or static free volume of the material. These effects are manifested in the parameters £act and Do. Depending on the temperature, the additive may either inhibit or facilitate oxygen diffusion relative to diffusion in the unperturbed, additivefree material. Data are reported for films containing dimethyl phthalate, diphenyl phthalate, cholestane, and molecular nitrogen as additives.

Singlet molecular oxygen (a1Δg) is shown to be the principal reactive intermediate in the photoinduced oxygen-dependent decomposition of a series of phenylenevinylene oligomers. The reaction rate between singlet oxygen and the oligomer decreases (1) with a decrease in the extent of phenylenevinylene conjugation (i.e., oligomer chain length) and (2) upon the incorporation of electron-withdrawing substituents on the oligomer. The reaction rate, however, does not appear to depend solely on the electron density of the oligomer π system, as calculated using ab initio methods. For oligomers with vinyl-substituted cyano group(s), the reaction with singlet oxygen is very slow, thus making such compounds good candidates for the production of stable electroluminescent materials.