Temperature dependence of fluorescent probes for applications to polymer materials processing

We have examined the temperature dependence of fluorescence spectra from dyes that can be used as molecular probes during polymer processing. The dyes, perylene and benzoxazolyl stilbene, are in a class of dyes called band definition dyes, so called because their fluorescence spectra contain distinct intensity peaks at characteristic wavelengths. The dyes were chosen for this study because they are soluble at dopant levels of concentration in organic Polymers at elevated temperatures and they survive without degradation at polymer processing temperatures up to 300degreesC. Changes induced in the fluorescence spectra over a range of typical processing temperatures were examined using statistical techniques that establish correlations between fluorescence intensity, wavelength, and temperature. The derived correlations are the basis for temperature calibrations that can be applied to process monitoring. A phenomenological model that assumes temperature dependence for both nonradiative and radiative decay modes is developed. A fit of the model parameters to the fluorescence spectra yielded activation energies for the temperature dependence of fluorescence decay rates.