Phase behaviour of oppositely charged polymer/surfactant mixtures

We demonstrate that many of the features of associative phase separation seen experimentally for oppositely charged polymer/surfactant mixtures can be recovered with a Poisson-Boltzmann cell model for macroion solutions, extended to incorporate a polyelectrolyte component. Whilst the phase transition is driven by entropy and electrostatic effects, we find that the extent of phase separation is sensitive to excluded-volume effects and to the short-range polymer-micelle interaction. Our model also makes predictions for trends in the critical aggregation concentration which are in reasonable agreement with experiment.