Interactions of micelles with fluorescence-labeled polyelectrolytes

Pyrene-labeled polyelectrolytes can be used to study the interaction betwee n the polyelectrolyte and an oppositely charged micelle, if the micelle inc orporates a fluorescence quencher. If the charge on the micelle is varied s ystematically, polymer-micelle complex formation can be observed at some we ll-defined micelle surface charge density. Applying a kinetic model to stea dy-state and time-dependent fluorescence quenching data, one can estimate t he binding constant (K), association rate constant, and lifetime (residence time). K increases strongly with increase in micelle surface charge densit y (sigma) or decrease in ionic strength (mu) These effects arise from the d ependence of association rate constant and residence time on sigma and mu. While these observations reflect the fundamental electrostatic nature of th e interaction, it is also found that micelles preferentially bind to pyrene sites, so that complex formation results from the conjoint action of elect rostatic and hydrophobic forces. (C) 1999 Elsevier Science B.V. All rights reserved.