Interactions between surfactants and polymers. II: Polyelectrolytes

We have studied the interactions between the polyelectrolytes Na+-κ-carrageenan (Carr) and diethylaminoethyl dextran (DEAE), and the surfactants alkylammonium bromide (RTAB, R=C16, C14), sodium dodecylsulfate (SDS), and sodium cholate (SC) in solution. The results of conductivity, fluorescence and turbidity measurements showed that hydrophobic aggregates were formed between oppositely charged polymers and surfactants even at very low amphiphile contentrations well below the normal CMC. At increased surfactant concentrations precipitates were formed. The SDS/DEAE complex could completely be redissolved at high surfactant concentrations. However, the SC/DEAE complex could only partially be resolubilized and the RTAB/CARR not at all. The results at low surfactant concentrations were simulated with the Poisson-Boltzmann equation in a cylinder model, showing the possibility of an electrostatically induced hydrophobic effect.