Interactions of hydrophobically modified polyelectrolytes with surfactants of the same charge

Polymer-surfactant interactions in aqueous solutions of a hydrophobically modified polymer, poly(maleic acid/octyl vinyl ether) (PMAOVE), with sodium dodecyl sulfate (SDS) were studied using surface tension, viscosity, electron paramagnetic resonance spectroscopy, and fluorescence spectroscopic techniques. When the anionic surfactant SDS was added to the aqueous solutions of the similarly charged polymer PMAOVE, the surfactant was incorporated into the hydrophobic nanodomains of PMAOVE far below the critical micelle concentration of the surfactant. Two inflection points were observed corresponding to the critical complexation concentration (formation of mixed micelles composed of SDS and the octyl chains of PMAOVE) and the saturation concentration (saturation of the polymer with SDS molecules). Above the saturation concentration, coexistence of pure SDS micelles and mixed micelles of PMAOVE and SDS was observed. At a PMAOVE concentration of 0.1% (w/w), a critical complexation concentration of 2 mM SDS and a saturation concentration of approximately 12 mM SDS were found; both the critical complexation concentration and the saturation concentration increase with increasing PMAOVE concentration.