Polyelectrolyte-induced peeling of charged multilamellar vesicles

We study mixtures of charged surfactants, which alone in solution form uni- and multilamellar vesicles, and oppositely charged polyelectrolytes (PEs). The phase behavior is investigated at fixed surfactant concentration as a function of the PE-to-surfactant charge ratio, x. We find that, for x > 0, aggregates form. Light microscopy and X-ray scattering experiments show that the isoelectric point plays a crucial role, since the morphology and the microscopic structure of the aggregates are different before (x < or = 1) and after the isoelectric point (x > 1). To better understand the dynamics for the formation of PE/surfactant complexes, we perform light microscopy experiments where we follow in real time the effect of a PE solution on one multilamellar vesicle (MLV). We find that the PE induces a peeling of the bilayers of the MLV one by one. The peeling is accompanied by strong shape fluctuations of the MLV and leads ultimately to a pile of small aggregates. This novel phenomenon is analyzed in detail and discussed in terms of PE-induced tension and pore formation and growth in a surfactant bilayer.