Alternating copolymers containing an aromatic chromophore in every monomer unit IV. Intramolecular triplet–triplet annihilation in copolymer of 9-phenanthrylmethyl methacrylate and 9-vinylphenanthrene in rigid solution

The total and delayed emission spectra of the alternating copolymer of 9-phenanthrylmethyl methacrylate (PhMMA) and 9-vinylphenanthrene (VPh) (a-PhVPh) in a rigid solution at 77 K were compared with those of poly(PhMMA-alt-styrene) (a-PhSt), poly(methyl methacrylate-alt-VPh) (a-MVPh), and the corresponding random copolymers. All the fluorescence, phosphorescence, and delayed fluorescence of a-PhVPh emitted predominantly from the phenanthryl chromophores in the VPh monomer units, indicating that energy transfer occurs from the PhMMA units to the VPh ones in both singlet and triplet states. In addition, the delayed fluorescence was the most intensive for a-PhVPh. A neglected amount of energy trap sites and an increased density of chromophores in the polymer chain may allow the long-distance triplet–triplet annihilation in this polymer. However, its high molecular weight, which would increase the probability of multiple excitations, was found to be the most important factor for the enhanced delayed fluorescence.