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Fluorescence study for the electrostatic interaction and aggregation in dilute polar solution of polyelectrolytes
Author(s) -
Sun Qilong,
Ren Biye,
Liu Xinxing,
Zeng Fang,
Liu Ping,
Tong Zhen
Publication year - 2003
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.200390034
Subject(s) - counterion condensation , counterion , pyrene , quenching (fluorescence) , chemistry , aqueous solution , fluorescence , polyelectrolyte , salt (chemistry) , analytical chemistry (journal) , mole fraction , polymer , ion , chromatography , organic chemistry , physics , quantum mechanics
Fluorescence decay and quenching of pyrene labels on copolymers of 2‐acrylamido‐2‐methylpropanesulphonic acid (AMPS) and N,N ‐dimethylacryl‐amide (DMAA) were observed in dilute salt‐free aqueous solutions as a function of the mole fraction F AMPS of AMPS from 0 to 0.896. Monoexponential and biexponential decays were found for the samples of F AMPS < 0.35 and samples of FAMPS > 0.35, respectively. The fast decay component is 80% and the averaged lifetime <τ> and lifetime τ 1 of the fast decay decreased with increasing F AMPS . Quenching efficiency of Cu 2+ , CH 3 NO 2 , and dinitrobenzene to the pyrene label was investigated in the framework of Stern‐Volmer plot. The quenching effects of Cu 2+ included both of dynamic and static ones, the latter was due to the condensed Cu 2+ . For the neutral quenchers, the quenching rate constant k q increased when F AMPS < 0.449 then decreased, showing a decline of accessibility to the pyrene label. I 1 / I 3 value in salt‐free dilute aqueous solution and in DMSO solution decreased obviously with an increase in F AMPS , indicating that the labeled fluorophore experienced a decrease in polarity of its microenvironment with increasing charge density of the polymer. This I 1 / I 3 decrease was enhanced with increasing the polymer concentration and adding salt NaCl up to 0.75 mol/L showed no effect on the appearance of this decrease. These results were interpreted consistently with the counterion condensation concept, where condensed counterions induced the “temporal” aggregation of less‐polar in the polyelectrolyte solutions surrounding the pyrene labels.