Fluorescence dynamics of poly(N-vinylcarbazole) in solution as revealed by multicomponent analysis of picosecond time-resolved fluorescence spectra: Dependence on tacticity and molecular weight

The steady-state fluorescence spectra of poly(N-vinylcarbazole) (PVCz) with various molecular weights in tetrahydrofuran solution were examined. The spectra of PVCz(r) prepared by radical polymerization were almost independent of the molecular weight, while those of PVCz(c) prepared by cationic polymerization were dependent on it. The difference in the temperature dependence of the spectra between PVCz(r) and PVCz(c) with high molecular weights was found. The time-resolved fluorescence spectra of PVCz(r) and PVCz(c) with high and low molecular weights were analysed by using a principal multicomponent spectral estimation method, whose results indicate clearly that the spectra were composed of only three component fluorescences (monomer, partial overlap excimer and sandwich excimer). The spectra were analysed by means of a least-squares fitting method using the three component spectral shapes, giving rise and decay curves of these component fluorescences. The curves were non-exponential and depended upon tacticity and the molecular weight. On the basis of these results, the excimer dynamics of PVCz in solution was discussed.