SEGREGATION IN AQUEOUS SYSTEMS OF A POLYELECTROLYTE AND AN IONIC SURFACTANT

Phase diagram studies have been carried out for systems of a polyelectrolyte and an oppositely charged surfactant in the presence of high concentrations of salt, and for systems of a polyelectrolyte and a surfactant with the same charge. All the systems studied display phase separation of the segregative type. In the former case, phase separation is facilitated by increasing either the alkyl chain length of the surfactant or the molecular weight of the polyelectrolyte. In the latter case, phase separation takes place in the absence of salt but is markedly enhanced by salt addition. An increased surfactant chain length and an increased polyelectrolyte molecular weight facilitates phase separation also in this case. For both types of system the tie lines are markedly skewed, an observation which cannot be explained by Flory-Huggings-type models.