Applications of the tachiya fluorescence quenching model to describe the kinetics of solid-state polymer photodegradation

The degradation reactions of polymers can be conveniently monitored spectroscopically using the metal bond chromophore. The degradation kinetics typically follow a biphasic decay in which there is a short, nonlinear component and a longer-lived, slowly evolving linear component. In one microenvironment, a fluorescence quencher is within the quenching sphere of the excited molecule, and this leads to quenching. In the second microenvironment, no quencher molecule is inside the quenching sphere, and no quenching will occur because diffusion into the quenching sphere is slow compared to the lifetime of the excited state. An important feature of Tachiya's suggestion is that it is not necessary to postulate that diffusion of a trap into the reaction sphere of the radical occurs during the lifetime of the radical in order to get biphasic behavior.