FLUORESCENCE STUDIES OF THE VACUUM-ULTRAVIOLET, SYNCHROTRON-RADIATION-INDUCED PHOTOCHEMISTRY OF POLYSTYRENE

The synchrotron radiation (SR) induced, vacuum ultraviolet (vacuum UV) photodegradation of polystyrene was studied by fluorescence spectroscopy. Two broad, structureless transitions were observed in the dispersed fluorescence spectrum of polystyrene when wavelengths shorter than 2200 angstrom were used to excite the polymer films: the first was centered at 3200 angstrom, and the second was centered at 5300 angstrom. The fluorescence excitation spectrum of each emission band has been recorded from 450 to 3000 angstrom and is compared to the optical absorption spectrum of polystyrene from 1050 to 3000 angstrom. The 3200-angstrom band is due to an excimer to ground state transition. The 5300-angstrom band is due to fluorescence from a conjugated backbone structure which forms when the polystyrene films are exposed to vacuum UV radiation. Changes were observed in both the fluorescence and fluorescence excitation spectra following exposure to 1200-angstrom or broad-band SR. Based on the data, a qualitative model is used to account for the degradation and energy transfer within the polystyrene films.