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

摘要

Polymer and surfactant self-diffusion have been measured by pulsed field gradient NMR in aqueous solutions of hydrophobically modified polyacrylamide (HM-PAM) and an unmodified polyacrylamide (PAM) analogue in order to investigate the binding of surfactant to polymer. The binding has also been calculated from surface tension measurements. The binding of sodium dodecyl sulfate (SDS) to the modified polymer in semidilute solutions displays a non-cooperative binding mechanism, while no such binding is detected for the PAM reference. The polymer self-diffusion decreases with increasing polymer concentration. At a surfactant concentration of ca. 7 mmolal (7 mm) a minimum for the polymer self-diffusion is observed. Previous rheological and present self-diffusion and surface tension results indicate a value of SDS addition for maximum effects on solution viscosity and polymer self-diffusion of approximately 7 mm.