Polyelectrolyte-surfactant complexes

The formation of the polyelectrolyte - surfactant complexes has been studied. On this purpose has been measured the critical micelle concentration for even, polyelectrolyte and surfactant which had been used. The phase behaviour of mixtures of a cationic polyelectrolyte (Praestol 611) and an anionic surfactant (sodium lauryl sulphate - SLS) has been studied. For a given polyelectrolyte concentration. with increasing surfactant concentration, three phase regions were identified. The first region is a single homogeneous phase. Within this region, at some surfactant concentration. above the critical aggregation concentration (cac), stable open - network 'particles' form, typically similar to 100 nm in size, which are net positively charged. However, as the surfactant concentration is increased further, these particles aggregate and form a two - phase system: a separated gel phase. containing a high percentage of water co-existing, with an aqueous surfactant phase. The theological consequences of interactions of polyelectrolytes with surfactants of the opposite charge are experimentally studied.