Quenching interchain-fluorescent

Ley and Schanze have also examined the luminescence properties of the polymers Pq, Pio> P25> and P50 in solution at 298 K, and in a 2-methyltetrahydro-furan solvent glass at 77 K. These spectroscopic studies reveal that fluorescence from the 71,71" exciton state is observed at Amax=443 nm, 2.80 eV in the polymers P0-P50 at 298 and 77 K, but the intensity and lifetime of the fluorescence is quenched as the mole fraction of Re in the polymers is increased. This indicates that the metal chromophore quenches the 71,71" state. The quenching is inefficient even when the mole fraction is large, suggesting that interchain diffusion of the 71,71" exciton is slow compared to its lifetime [70]. Phosphorescence from the 71,71" state of the conjugated polymer backbone is observed at > max=b43 nm, 1.93 eV in P10-P50 at 77 K, and emission at Amax=690 nm, 1.8 eV is assigned to the d7i(Re) 7i oiy MLCT transition. 

Thin films only exhibited very weak fluorescence. This suggests the formation of strong interchain interaction in the solid state, leading to fluorescence self-quenching. 

The Ksv values for these ions are similar to those for Cu2+ and it may be anticipated that binding to the polymer by all three ions occurs with comparable strength due to reasonably similar Coulombic interactions between the divalent ions and the polymer. Since the polymer fluorescence is known to be strongly attenuated when interchain or intermolecular interactions occur, it may be that all or part of the quenching observed for these ions may be attributed to aggregation effects induced by association of the divalent cations with the polymer. 

Fluorescent hydrophobes (naphthyl and pyrenyl groups) incorporated into the polysulfobetaines are a powerful tool for studying the formation of intra-and interpolymer aggregates in aqueous and aqueous salt solutions [85,229-231]. Intermacromolecular hydrophobic association is observed as an increase in the excimer emission relative to that of the monomer emission, where h/Iu is the ratio of intensities of excimer and monomer fluorescence which reflects the extent of inter/intra macromolecular interactions. Intramolecular micellization is easily monitored by the quenching efficiency of the thallium ions. The decrease of h/Iu reflects the breaking of the intra- and interchain associations in aqueous salt solutions, leading to chain expansion. 

Figure 2. Highly stable sensor polymer designed to bind and detect TNT and DNT. The rigid three dimensional structure provides for interchain spacing that prevents fluorescence quenching and allows for the formation of galleries capable of binding nitroaromatics.

The it-conjugated compounds 8 (aaaa 8a and apap 8b) are constructed by the introduction of four phenylenediamine pendant strands to the me t -positions of the atropisomeric porphyrin scaffolds (Fig. 3.4) [33]. In the fluorescence emission spectra, the emission from the porphyrin moiety is almost completely quenched in both atropisomers. This process is more efficient than that of the porphyrin bearing one pendant group, suggesting the interchain interaction of 8 [34]. 

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