The photosensitized production of singlet molecular oxygen (1.DELTA.gO2) in a solid organic polymer glass: a direct time-resolved study

The photosensitized production of singlet molecular oxygen (/sup 1/..delta../sub g/O/sub 2/) has long been a subject of scientific study. Recently, direct evidence for the presence of /sup 1/..delta../sub g/O/sub 2/ in thin (10-30 ..mu..m) polymer films was obtained by Byteva et al. who detected /sup 1/..delta../sub g/O/sub 2/ phosphorescence (/sup 3/..sigma../sub g//sup -/O/sub 2/ reverse arrow /sup 1/..delta../sub g/O/sub 2/: 1270 nm) in a steady-state photosensitized experiment. In a time-resolved study, /sup 1/..delta../sub g/O/sub 2/ has also been observed in a heterogeneous ionomer system (Nafion powders) in which the /sup 1/..delta../sub g/O/sub 2/ sensitizer was apparently located at the surface of solvent filled or dessicated cavities. They now report that /sup 1/..delta../sub g/O/sub 2/ phosphorescence can be detected in a time-resolved photosensitized experiment from a homogeneous, solid polymethylmethacrylate (PMMA) glass. As in the solution phase, they expect this technique will become an indispensable tool in studies of /sup 1/..delta../sub g/O/sub 2/ photophysics and photochemistry. In particular, the role of /sup 1/..delta../sub g/O/sub 2/ in the photooxidation and photodegradation of solid polymers has been a focus of debate. Since they directly monitor molecular oxygen, this experimental approach also provides a unique method to accurately quantify oxygen diffusion in a polymer.