Photophysical processes and interactions between poly(ethylene terephthalate) and 1-amino-2-(2-methoxyethoxy)-4-hydroxy-9,10-anthraquinone

The effect of 1-amino-2-(2-methoxyethoxy)-4-hydroxy-9,10-anthraquinone (C. I. Disperse Red 59) on the phototendering of poly(ethylene terephthalate) (PET) was assessed. The photophysical processes occurring in the polymer, the dye, and the dyed polymer were determined. The energy and nature of the dye and polymer electronic excited states were assigned on the basis of absorption and luminescence properties. Irradiation failed to produce dye-sensitized phototendering of PET; however, the titanium dioxide delusterant in commercial PET did function as a sensitizer in the presence of moist air. The phototendering of blank-dyed PET yarn was found to obey (pseudo-) zero-order kinetics k = 1.69 × 10^?19 per cent breaking strength loss/quantum absorbed/cm². The dye exhibited fluorescence from a lowest, ～51.5 kcal/mole, singlet charge-transfer (C-T) excited state but did not phosphoresce. The PET possessed a complex fluorescence spectrum attributed to similar ¹(n,π^*)₁ excited states, ～78.1 kcal/mole, while its phosphorescence derives from a proposed ³(π,π^*) state, ～69.8 kcal/mole, populated by intersystem crossing from a ¹(π,π^*) state, ～92.3 kcal/mole. The dyed polymer exhibited a PET-sensitized delayed fluorescence from the dyestuff involving triplet–singlet transfer by a dipole–dipole (Coulumbic) long-range resonance excitation mechanism. The transfer process was characterized by an experimentally determined critical transfer distance, R₀, of approximately 40 Å.