Modulation of Polyelectrolyte–Micelle Interactions via Zeta Potentials

Abstract

The onset of soluble complex formation between polycations and nonionic/anionic mixed micelles was found to occur at well-defined micelle surface charge density, σc, which could be modulated via Y, the mole fraction of anionic surfactant in the mixed micelle. Critical values of Y were detected by precision turbidimetry for two polycations, each combined with any of the four mixed micelles formed from two anionic and two nonionic surfactants. The values of Yc observed for each of the resultant eight ternary polycation/anionic–nonionic combinations were used as surrogates for polycation binding affinity: for a given polycation and a given value of Y, micelles with Yc Y will not. The polycation affinity of micelles correlated with their “zeta potentials” (ζ), measured by electrophoretic light scattering, and their average surface potentials (ψ0), measured by potentiometric titration of a comicellized probe. For a given polycation at a fixed ionic strength, we found that t...