THE ABSENCE OF CONVENTIONAL POLYMER-SURFACTANT INTERACTION BETWEEN SODIUM MONODECYL PHOSPHATE AND POLY(ETHYLENE OXIDE) - CONDUCTIVITY AND KINETIC EVIDENCE

Mixtures of sodium monodecyl phosphate (NaDeP) and poly(ethylene oxide ) (PEG) have been investigated conductimetrically in 0.05 M succinate buffer, pH 5.20. The conductivity vs NaDeP concentration profiles do n ot show the classical behavior of PEO-sodium dodecyl sulfate (SDS) mix tures. In the presence of different concentrations of PEG, the profile s exhibit only one discontinued point, whose SDS concentration values are similar to the NaDeP critical aggregation concentration. It was ob served also that this conductivity breakpoint is not sensitive to vari ation in the polymer concentration and that it is independent of polym er molecular weight. However, the conductivity profiles of mixtures of NaDeP and SDS demonstrate behavior similar to that of SDS alone. For these mixtures, the evidence of binding, absent in the presence of NaD eP alone, is interpreted by assuming that it is solely driven by the S DS. (C) 1997 Academic Press.