Modelling excimer formation in vinyl aromatic polymers

Abstract

This study has found that the Fredrickson and Frank (FF) model of excimer 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 of a high “pre-formed trap” concentration, a model using the first passage time (FPT) approach is developed, which has greater accuracy in the high “pre-formed trap” concentration regime. Fits to experimental data are presented which demonstrate that the FPT model produces the same parameters as the FF model under certain conditions. The uniqueness of both the FF and FPT models were also assessed and conditions found under which a simpler, stretched exponential model is an adequate approximation. The approximation is tested with both synthetic and experimental data, confirming that under many conditions FF and FPT are indistinguishable from the simpler model. Conditions are found under which the FF and FPT models may be distinguished from a mass diffusion model.