The thermochromism of a polyfluorene derivative complexed with a europium ion was interpreted using the photophysical properties of the noncomplexed polymer and a low molecular mass model compound having the same structure of the complexed site in the polymer. To the naked eye, the thermochromism was characterized by a strong red at low temperatures (170− 260 K, due to Eu 3+ ion) and a blue color at higher ones (280−330 K, due to fluorene). Absorption and emission spectra, time-resolved measurements, and theoretical simulations showed that the polymer chain does not affect the europium photophysical properties, but the opposite occurred: the ion insertion precluded interchain aggregation, and the backbone emission did not vary with temperature variation, in the range of 170−330 K. To the best of our knowledge, this effect is reported for the first time and opened a new avenue for the design of nanothermometers, since the polymer can act as a "built-in standard", thus allowing the construction of much simpler devices.
A fluorescent silicone network was prepared by a hydrosilylation reaction using poly(dimethylsiloxane-co-methylhydrogensiloxane) terminated by dimethylhydrogensilyloxy groups, poly(dimethylsiloxane-co-methylvinylsiloxane) terminated by dimethylvinylsilyloxy groups and 9-vinylanthracene, as the fluorescent group. These silicone-based materials were strongly fluorescent. Steady state emission was a convenient technique to prove that reaction occurred, based on the blueshift of the emission from anthracenyl moieties compared with the 9-vinylanthracene. Thermal transitions were studied by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and by fluorescence spectroscopy, indicating that networks with and without lumophores had similar thermal properties. Networks with and without lumophores had the same swelling capability in toluene. Fluorescence spectroscopy was a more sensitive technique to the onset of the glass transition temperature (T ¼ 145 K) than DSC or DMA. Nevertheless, the crystallization temperature at 192 K was determined more precisely by DSC, and the melting point at 237 K was indentified more clearly by both DSC and DMA. These three techniques provided complementary information about transitions in silicone networks. V C 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: [74][75][76][77][78][79][80][81] 2010
We report the synthesis, characterization, and organic light-emitting diode (OLED) application of the first example of a platinum poly-yne (NPtAP) featuring N-heterocyclic carbene (NHC) ligands. NPtAP was synthesized via the Cu(I)-catalyzed AA/BB type polymerization reaction with M n = 8400 g mol −1 and Đ = 1.6. The bulky and strong σ-donating NHC ligands bearing chiral 2-ethylhexyl substituents help to limit the interchain interaction and destabilize the nonemissive metal-centered d−d state, resulting in enhancement of the photoluminescence quantum yield of the platinum poly-yne. The prototype solution-processed OLEDs employing NPtAP as the emitter were successfully fabricated and display yellowgreen electroluminescence (EL).
The synthesis and photophysical characterization of a PPV-type copolymer containing a fluorene derivative alternated with thiophene units is presented: poly(9,9'-dioctylfluorene-thiophene) (LAPPS29). Photophysical studies demonstrated that in the solid state only preformed ground state aggregates are responsible for exciton formation. These aggregates are formed with a wide range of size distribution. The emission from isolated segments is quenched either by resonant energy transfer, or by migration processes. Also, the main photovoltaic parameters are discussed in connection with the photophysical behavior.
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