Emission Spectra of the Vinyl Polymers with Pendant Benzocarbazolyl Groups

Abstract

The emission spectra of poly(N-vinyl-5H-benzo[b]carbazole) (PV5BCz) and poly(N-vinyl-7H-benzo[c]carbazole) (PV7BCz), which are prepared by radical and cationic polymerization, and their monomeric model compounds were investigated in solutions. In the case of PV7BCz, the fluorescence spectra were composed of a second excimer fluorescence at the shorter wavelength and a sandwich-like excimer fluorescence at the longer wavelength. The difference in the spectra between the radical and cationic polymers was quite similar to that of the poly(N-vinylcarbazole) (PVCz) system. The intensity of the sandwich-like excimer fluorescence was independent of the polymerization methods, but the intensity of the second excimer fluorescence increased with an increase in the content of the syndiotactic sequence. In the case of PV5BCz, the behavior of the fluorescence spectra of the radical polymers was similar to that of the PVCz and PV7BCz systems. On the other hand, the fluorescence spectra of the cationic polymers differed markedly from those of the above-mentioned polymers. The cationic polymers did not show the second excimer fluorescence, but a monomer-like structured fluorescence, at the shorter wavelength, although it did show the sandwich-like excimer fluorescence at the longer wavelength. This significant difference in the fluorescence spectra between the radical and cationic polymers is attributable to the difference between their tacticities. On the basis of these results, the characteristics of the second excimer site were further clarified.