Complex Formation between Polyelectrolyte and Oppositely Charged Mixed Micelles

Electrophoretic light scattering, dynamic light scattering, turbidity, and static light scattering were used to study complex formation between poly(dimethyldiallylammonium chloride) (PDMDAAC) and oppositely charged mixed micelles of Triton X-100 (TX100) and sodium dodecyl sulfate (SDS) in 0.4 M NaC1. Interpolymer complexes form with an increasing bulk weight ratio of PDMDAAC to TX100-SDS, W, at constant [TXlOO-SDS]. The turbidity, scattered light intensity, and apparent hydrodynamic radius of the complexes all reach maxima at W * 0.09. This value of W corresponds to a net charge ratio of PDMDAAC to TX100-SDS of 1:l. Electrophoretic light scattering indicates that the electrophoretic mobility of the complexes changes from negative to positive with increasing W and is close to zero around W 0.09. However, neither precipitation nor coacervation is observed, in contrast to typical polyelectrolyte-oppositely charged surfactant systems. The results support a model for the complex wherein only a fraction of the charged residues are associated with corresponding charges on the TX100-SDS mixed micelles.