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 b ind to the polycation PDADMAC at a well-defined critical pH corresponding t o a critical micelle surface charge density a,. The ionic strength dependen ce of sigma (c) for this and a number of related polyelectrolyte-micelle sy stems conforms to the simple result sigma (c) =A kappa (1.4), where kappa i s the Debye-Huckel parameter and A varies inversely with polymer linear cha rge density. The interdependence of sigma (c) and kappa also leads to the o bservation that binding occurs when the potential due to the micelle exceed s -9 mV at a distance of 8 Angstrom from the micelle surface.