Molecular weight dependence of triplet—triplet processes in poly(2-vinylnaphthalene)

Delayed fluorescence and phosphorescence spectra and decay curve measurements at 77 K are reported for samples of poly(2-vinylnaphthalene) with molecular weights determined by viscometry to be in the range 15 600 to 505 000. The intensity of delayed fluorescence relative to phosphorrescence was found to increase with molecular weight up to the highest molecular weight sample of solution polymerized material (MW ≈ 100 000) with a leveling off for the higher molecular weight bulk polymers. It is argued that these results imply a triplet exciton migration distance of up to 700 chromophore units. Decay curves imply that most mobile triplet excitons are trapped within approximately 0.3 s. The excitation dependence of the delayed emissions imply that unimolecular processes dominate the kinetics of triplet state chromophores.