TRIPLET EXCIMER MONOMER EQUILIBRIA AS STRUCTURAL PROBES IN PURE AND MOLECULARLY DOPED POLYMERS

Solid films of vinyl aromatic polymers usually emit an excimeric type of phosphorescence at temperatures of 77 K or greater. At temperatures near 10 K these emission spectra are definitely nonexcimeric and at intermediate temperatures the two types of emission coexist. Using the assumption that triplet excimers are formed by trapping at an excimer-forming site, activation energies have been determined for both trapping and detrapping by measuring rates of decay of the excimeric and nonexcimeric emission. The activation energies for trapping of a given chromophore are independent of whether that chromophore is bonded to a chain backbone or present as a small molecule dopant in a polystyrene matrix. The activation energies for detrapping are potentially valuable as an indicator of microstructure for polymers containing a chromphoric group that is phosphorescent.