Interactions among hydrophobically modified polyelectrolytes and surfactants of the same charge

Effects of sodium dodecyl sulfate (SDS) on surface tension and rheology of aqueous solutions of an associative polymer, poly(ethylene oxide)-b-poly(pr opylene oxide)-b-(poly(ethylene oxide))-g-poly(acrylic acid) (Pluronic-PAA) have been studied. SDS starts to bind to the Pluronic-PAA copolymer at a c oncentration that is 25-fold lower than the critical micellization concentr ation (CMC) of the surfactant. The data indicate predominant binding betwee n SDS and polyether segments of Pluronic-PAA. Incorporation of SDS into the Plutonic micelles makes the polymer less surface-active, as the surface te nsion increases. The Pluronic-PAA chains collapse when SDS binds, because t he surfactant enhances hydrophobic intramolecular associations.