Synthesis, photophysical properties and thermal relaxation processes of carbazolyl-labeled polysiloxanes

The photophysical properties of a fluorescent silicone prepared by a hydrosilylation reaction from poly(dimethylsiloxane-co-methylhydrogensiloxane) terminated by dimethylhydrogensilyloxy groups, poly(dimethylsiloxane-co-methylvinylsiloxane) terminated by dimethylvinylsilyloxy groups and 9-vinylcarbazole, as the luminescent group, have been studied under steady-state fluorescence and time-resolved conditions. At low temperature both steady-state fluorescence and phosphorescence spectra of isolated species are observed. Phosphorescence is quenched at temperatures higher than 150 K indicating that the environments where the carbazolyl moieties are located are very flexible, as expected for silicones. Fluorescence decays and phosphorescence (at 77 K) showed typical carbazolyl lifetimes and no rise-time was observed, which is consistent with the absence of excimer emission. The temperature dependence of the emission can be used to determine the polymer relaxation processes and transitions (Tγ = 80-100 K, Tg = 130-150 K and Tm = 220 K), these last two comparable with those observed by differential scanning calorimetry.