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(propylene 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 concentration that is 25-fold lower than the critical micellization concentration (CMC) of the surfactant. The data indicate predominant binding between SDS and polyether segments of Pluronic-PAA. Incorporation of SDS into the Pluronic micelles makes the polymer less surface-active, as the surface tension increases. The Pluronic-PAA chains collapse when SDS binds, because the surfactant enhances hydrophobic intramolecular associations.