Interactions of micelles with fluorescence-labeled polyelectrolytes

Abstract

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 (|) or decrease in ionic strength (v). These effects arise from the dependence of association rate constant and residence time on | and v. 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.

Steady-State and Time-Dependent Fluorescence Quenching Studies of the Binding of Anionic Micelles to Polycation

“…Turbidimetric, light scattering, and fluorescence studies using a copolymer of sodium 2-(acrylamido)-2-methylpropanesulfonate (AMPS) (99 mol %) and N-(1-pyrenylmethyl)-methacrylate (PyMAm) (1 mol %), PyPAMPS, as a pyrenelabeled polyanion revealed that the interaction of PyPAMPS with mixed micelles of dodecyl hexa(ethylene glycol) monoether (C 12 E 6 ) and cetyltrimethylammonium chloride (CTAC) occurred preferentially with pyrene sites, although the interaction was predominantly driven by electrostatic attractions. [33][34][35] These results indicate a conjoint effect of hydrophobic and electrostatic interactions on the polyion-micelle interaction. [33][34][35] The preferential binding of C 12 E 6 /CTAC mixed micelles to hydrophobic sites incorporated into a polyanion was confirmed in a systematic study using terpolymers of AMPS, PyMAm (1 mol %), and N-dodecylmethacrylamide (0-7.5 mol %) in conjunction with C 12 E 6 /CTAC mixed micelles in which cetylpyridinium chloride (CPC) is solubilized.…”

“…[33][34][35] These results indicate a conjoint effect of hydrophobic and electrostatic interactions on the polyion-micelle interaction. [33][34][35] The preferential binding of C 12 E 6 /CTAC mixed micelles to hydrophobic sites incorporated into a polyanion was confirmed in a systematic study using terpolymers of AMPS, PyMAm (1 mol %), and N-dodecylmethacrylamide (0-7.5 mol %) in conjunction with C 12 E 6 /CTAC mixed micelles in which cetylpyridinium chloride (CPC) is solubilized. 36 All of these results indicate that when fluorescence-labeled polyelectrolytes are employed to investigate the dynamics of the complex formation, the hydrophobic contributions from fluorescence-label sites are inevitable, although fluorescence quenching techniques are a powerful tool for studies of polyelectrolyte-micelle interactions.…”

“…[33][34][35][36] Among these methods, fluorescence techniques are expected to provide a powerful tool to gain insight into the dynamics of polyelectrolyte-micelle interactions. Recently, we used a pyrene-labeled polyanion in conjunction with quencher-carrying mixed micelles to characterize the microscopic polyelectrolytemicelle phase transition.…”

“…Recently, we used a pyrene-labeled polyanion in conjunction with quencher-carrying mixed micelles to characterize the microscopic polyelectrolytemicelle phase transition. [33][34][35][36] The intensity of the polyelectro- † Part of the special issue "Noboru Mataga Festschrift". ‡ Current address: Shiseido Basic Research Center, 2-2-1 Hayabuchi, Tsuzuki, Yokohama 224-8558, Japan…”

“…A previously proposed kinetic model 35,36 was used to interpret steady-state and time-dependent fluorescence quenching data, which made it possible to examine the residence time of the micelle in the polymer-micelle complex as a function of the micelle charge density and the ionic strength. Such measurements may be directly comparable to the results of Monte Carlo simulations.…”