CHAIN HETEROGENEITY AND LUMINESCENCE OF P OLY(ETHYLENE-TEREPHTHALATE)

Poly(ethylene terephthalate) films and polycrystalline powder of terep hthalic acid (TPA) were found to exhibit the same fluorescent properti es. The nature of the optically active centers in TPA and PET was esta blished. The TPA molecules exhibit no intrinsic fluorescence. The fluo rescence spectra of TPA powders depend on the degree and method of pur ification, which suggests the emitting centers to be associated with t he presence of impurities. On the basis of the published data on the p resence of various side products of TPA synthesis in the powdered acid , the optically active centers responsible for the emission in the 360 - 440 nm region were identified as trace amounts of dicarboxystilbene , and those responsible for the emission in the 320 - 380 nm region, w ere identified as trace amounts of dicarboxydiphenyl. The corresonding optically active centers in PET were interpreted as molecular chain d efects, formed as a result of the participation of the above dicarboxy compounds in the polymeriozation reaction. The concentration of the d efects in the molecular chain is insignificant, and is manifested to a significant extent only in the fluorescence spectra.