Interactions of micelles with fluorescence-labeled polyelectrolytes

Pyrene-labeled polyelectrolytes can be used to study the interaction between the polyelectrolyte and an oppositely charged micelle, if the micelle incorporates a fluorescence quencher. If the charge on the micelle is varied systematically, polymer-micelle complex formation can be observed at some well-defined micelle surface charge density. Applying a kinetic model to steady-state and time-dependent fluorescence quenching data, one can estimate the binding constant (K), association rate constant, and lifetime (residence time). K increases strongly with increase in micelle surface charge density (sigma) or decrease in ionic strength (mu) These effects arise from the dependence of association rate constant and residence time on sigma and mu. While these observations reflect the fundamental electrostatic nature of the interaction, it is also found that micelles preferentially bind to pyrene sites, so that complex formation results from the conjoint action of electrostatic and hydrophobic forces. (C) 1999 Elsevier Science B.V. All rights reserved.