Triplet Excitation Energy Transfer in the Vinyl Polymers with Pendant Carbazolyl Groups

Abstract

Abstract The triplet energy transfer in poly(N-vinylcarbazole)(PVCz) prepared by radical and cationic polymerization (PVCz(r) and PVCz(c) respectively), poly[2-(N-carbazolyl)ethyl vinyl ether](PCzEVE), and brominated PVCz (BPVCz) has been investigated by measuring the delayed emission spectra in solid films and rigid solutions at 77 K. The prompt and delayed fluorescence spectra both in the solid film and in the rigid solution at 77 K were different for PVCz(r) and PVCz(c). This seems to be due to the difference in tacticity between them. PCzEVE, in which the Cz groups are connected from afar to the skeletal chains by means of –O–CH2–CH2–bonds, showed the delayed fluorescence and the phosphorescence both in the rigid solutions and in the solid films at 77 K. The BPVCz film showed only the excimer phosphorescence. In the solid films of PVCz(r), PVCz(c), and PCzEVE, the Cz chromophore-delayed fluorescence increased with an increase in the concentration of triplet quenchers, such as naphthalene and fluorene. This phenomenon suggests the presence of a heterogeneous triplet-triplet annihilation in these aromatic vinyl polymer films. The quenching of the Cz chromophore phosphorescence both by the doping of the naphthalene in the solid films and by the doping of the 1,3-pentadiene in the rigid solutions obeyed the Stern-Volmer equation, and the migration coefficient, λ, and the mean exciton migration length, L, were obtained. The values of λ and L were in the following order; PVCz(r)>PVCz(c)>PCzEVE (>BPVCz) in the solid film and PVCz(r)>PVCz(c) in the rigid solutions. The order was explained by both the concentration of the intrinsic trap sites for triplet excitons and the distance between neighboring Cz chromophores in one polymer chain.