DIFFUSE-REFLECTANCE LASER PHOTOLYSIS AND LUMINESCENCE STUDY ON POLY(ETHYLENE-TEREPHTHALATE) POWDER

Photochemical and photophysical primary processes of solid poly(ethyle ne terephthalate) powder were investigated with nanosecond diffuse ref lectance laser photolysis and conventional steady-state luminescence t echniques. The existence of four transient species was confirmed. To a ssign these transients, dependencies of the transient absorption spect ra and decay kinetics on foreign gas, dopant aromatic compounds which act as a photosensitizer or quencher, and crystallinity were investiga ted. In addition, the temperature effect was examined. As a result, th e transient species, observed only under an aerated condition, was ass igned to the precursor species leading to the photooxidation or photod egradation reaction. Other transient species were assigned to three di fferent triplet states, which correspond to three different local stru ctures: monomer site, dimer site, and a site which forms an excimer in the excited singlet state. The generation of three different triplet states is ascribed to an inhomogeneity of the aggregation and relative orientation of the monomer unit. It is discussed that crystalline and amorphous regions, and their boundary region, have a key role in phot ochemical and photophysical in polymer powder.