MODELING EXCIMER FORMATION IN VINYL AROMATIC POLYMERS

This study has found that the Fredrickson and Frank (FF) model of exci mer formation in polymers is adequate to describe fluorescence decays of selected polymers at low temperatures, but is inadequate at higher temperatures. Considering that the FF model could break down because o f a high ''pre-formed trap'' concentration, a model using the first pa ssage time (FPT) approach is developed, which has greater accuracy in the high ''pre-formed trap'' concentration regime. Fits to experimenta l data are presented which demonstrate that the FPT model produces the same parameters as the FF model under certain conditions. The uniquen ess of both the FF and FPT models were also assessed and conditions fo und under which a simpler, stretched exponential model is an adequate approximation. The approximation is tested with both synthetic and exp erimental data, confirming that under many conditions FF and FPT are i ndistinguishable from the simpler model. Conditions are found under wh ich the FF and FPT models may be distinguished from a mass diffusion m odel.