Polymer and Materials Science
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
The quenching of pyrene fluorescence by nitromethane, Tl+, Cu2+, I-, and 4-dimethylaminopyridine (DMAP) in aqueous solutions of a pyrene substituted poly(acrylic acid) (1) was influenced by the “polyelectrolyte effect” of 1. The efficiency of quenching in solutions of 1 was measured in terms of the Stern-Volmer constants for dynamic and static quenching which were obtained from comparison of the intensity and lifetime of pyrene fluorescence in solutions of 1 and a monomer model compound. The efficiency of quenching in solutions of 1 was always greater at high pH (9) in comparison to that at low pH (4). The ionization of carboxylic groups in 1 caused an expansion of the polymer mainchain and concomitant exposure of the pyrene molecules to the aqueous phase and quencher. The polyanion domain of 1 favored the condensation of cationic quenchers and could account for very efficient quenching in case of Cu2+ and Tl+. A very efficient quenching of pyrene fluorescence in solutions of 1 by DMAP at high pH was attributed to the hydrophobic interactions of DMAP and pyrene moiety. The iodide ions were less efficient quenchers of pyrene fluorescence due to electrostatic repulsion from the polyanion. The efficiency of quenching by nitromethane was not significantly affected by ionization of the carboxylic groups in 1.
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