Polymer self-diffusion and surfactant binding in aqueous solutions of unmodified and hydrophobically modified polyacrylamide studied by pulsed field gradient NMR and surface tension measurements

Polymer and surfactant self-diffusion have been measured by pulsed field gr adient NMR in aqueous solutions of hydrophobically modified polyacrylamide (HM-PAM) and an unmodified polyacrylamide (PAM) analogue in order to invest igate the binding of surfactant to polymer. The binding has also been calcu lated from surface tension measurements. The binding of sodium dodecyl sulf ate (SDS) to the modified polymer in semidilute solutions displays a non-co operative binding mechanism, while no such binding is detected for the PAM reference. The polymer self-diffusion decreases with increasing polymer con centration. At a surfactant concentration of ca. 7 mmolal (7 mm) a minimum for the polymer self-diffusion is observed. Previous rheological and presen t self-diffusion and surface tension results indicate a value of SDS additi on for maximum effects on solution viscosity and polymer self-diffusion of approximately 7 mm.