PET-co-4,4 -BPDC

Photophysical Processes in Pol,y(ethy1eneterephthalate-co-4,4 -biphenyldicarboxyl ate) (PET-co-4,4 -BPDC). The absorption and luminescence properties of PET are summarized above. At room temperature the absorption spectrum of PET-co-4,4 -BPDC copolymers, with concentrations of 4,4 -BPDC ranging from 0.5 -5.0 mole percent, showed UV absorption spectra similar to that of PET in HFIP. The corrected fluorescence spectra of the copolymers in HFIP exhibited excitation maxima at 255 and 290 nm. The emission spectrum displayed emission from the terephthalate portion of the polymer, when excited by 255 nm radiation, and emission from the 4,4 -biphenyldicarboxylate portion of the polymer when excited with 290 nm radiation. 

Phototendering of PET and PET-co-4,4 -BPDC Filament Yarns. Both "P T homopolymer and PET-co-4,4 -BPDC copolymers were irradiated from 20 to 80 hours in the photolysis chamber. In order to account for the lamp aging, the phototendering rate curves were plotted as percent loss tenacity versus total quanta/cm2 of exposure, rather than irradiation time. The phototendering rate curves for the homopolymer PET and PET-co-4,4 -BPDC copolymers show that all the samples became weaker and showed a decrease in percent elongation to break as total quanta/cm of exposure was increased (Figure 21). 

Fluorescence Analysis of Irradiated PET and PET-co-4,4 -BPDC Yarns. The presence of a material, which emits a blue-green fluorescence, on photooxidized PET has been reported previously (2, 21). This fluorescent material, which emits at 460 nm when excited by 342 nm energy, has been proved to be monohydroxy-tere-phthalate. 

In the yarns, the fluorescence of the 4,4 -biphenyldicarboxy-late unit is distinct and predominate both at 298 and 77°K. Examination of the phosphorescence spectra of the PET and PET-co-4,41-BPDC yarns revealed three emission maxima. In the PET homopolymer excitation with 310 nm radiation produced an emission at 452 nm from the terephthalate chromophore. In the copolymers excitation with either 305 or 310 nm radiation produced emission spectra with distinct maxima at 480 and 515 nm (t 1.2 sec), and a shoulder near 452 nm (t = 1.2 sec). The maxima in the phosphorescence spectra were assigned as emission from the 4,4 -biphenyldicarboxylate units of the copolymer. The observed emissions are bathochromatically shifted from the emission of 4,4 -BPDC in a glassed solvent. This is supported by the observed emissions from solid 4,4 -BPDC at 520 and 560 nm (t =. 3 sec) when excited with 340 or 356 nm radiation. 

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