The triplet state of the ladder-type methyl-poly(p-phenylene) as seen by pulse radiolysis-energy transfer

The lowest triplet state of a ladder poly(p-phenylene) (MeLPPP) has been pr oduced by sensitised energy transfer following pulse radiolysis of benzene solution, and absorbs at 1.34 eV with a lifetime greater than or equal to 1 70 mu s. An S-0-T-1 energy separation of 2.15 +/- 0.07 eV was determined, i n excellent agreement with recent phosphorescence measurements, confirming the validity of the technique for the determination of the triplet energies of conjugated polymers. At high triplet populations intrachain triplet-tri plet annihilation (TTA), leading to delayed fluorescence (DF) occurs. The D F spectrum is in good agreement with the prompt fluorescence and the DF kin etics support a TTA mechanism. (C) 2000 Elsevier Science B.V. All rights re served.