Binding of Carboxy-Terminated Anionic/Nonionic Mixed Micelles to a Strong Polycation: Critical Conditions for Complex Formation

Mixed micelles of carboxy-terminated surfactants and nonionic surfactants bind to the polycation PDADMAC at a well-defined critical pH corresponding to a critical micelle surface charge density σ c . The ionic strength dependence of σ c for this and a number of related polyelectrolyte−micelle systems conforms to the simple result σ c = A κ 1.4, where κ is the Debye−Hückel parameter and A varies inversely with polymer linear charge density. The interdependence of σ c and κ also leads to the observation that binding occurs when the potential due to the micelle exceeds −9 mV at a distance of 8 Å from the micelle surface.