The viscosity of aqueous solutions of poly(ethyleneoxide) (PEO) in the dilute and semidilute regimes exhibits a maximum as a function of sodium dodecyl sulfate (SDS) concentration. The maximum is shown to correspond to the point at which the polymer coils are saturated with surfactant. From intrinsic viscosity and small angle neutron scattering (SANS), we obtain a value of 0.65 for the excluded volume exponent of PEO at saturation. Carbon-13 nuclear magnetic resonance (NMR) relaxation measurements indicate that the correlation time for local segmental motion for polymer segments attached to micelles is reduced from about 10−11 to 10−9 s. However, only a relatively small fraction of the total coil is in direct contact with the micelles at saturation. A model for the polymer–surfactant complex is presented based on these considerations.

The adsorption of sodium dodecyl sulfate (SDS) and poly(viny1pyrrolidone) (PVP) at the air/water interface from an aqueous solution containing both components is studied by using the radiotracer technique and surface tension measurements. The increase in surface tension accompanying the conversion of a micellar solution of SDS (in the presence of M NaCI) to a solution containing PVP-SDS assemblies in the bulk phase by the addition of PVP is explained on the basis of desorption of SDS and adsorption of the polymer at the air/water interface. The concentration of SDS at the interface is reduced to 2/3 of the value in the absence of the polymer. The results suggest that SDS and PVP form two-dimensional aggregates at the interface similar in structure to the assemblies in the bulk phase. IntroductionIn recent years, a number of papers'-3 have dealt with the properties of aqueous solutions containing a mixture of nonionic polymer and anionic surfactant. The most widely studied systems have been those containing poly(ethy1ene oxide) (PEO) and sodium dodecyl sulfate (SDS) or poly(vinylpyrro1idone) (PVP) and SDS. The changes occurring in bulk water upon the addition of PVP or PEO to a micellar solution of SDS are now well-characterized in terms of the structure of the polymer-surfactant complex that is formed and also in terms of the distribution of surfactant between the monomer or free amphiphile state and the aggregate ~t a t e .~*~ In contrast, no attempt has been made to

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The influence of sodium dodecyl sulfate (SDS) on the conformation of poly(ethylene oxide) (PEO) in water is studied using viscosity measurements and small-angle neutron scattering (SANS). The behavior, as a function of surfactant concentration above the critical aggregation concentration (CAC), can be described in terms of two separate regimes: an initial regime in which micelles are attached to the coils but are noninteracting and a second regime in which there is interaction between the attached micelles. The latter is characterized by a strong increase in viscosity and other features similar to polyelectrolytes. On the contrary, in the initial regime, our results suggest a slight decrease in coil size under ambient conditions and a much more significant decrease at elevated temperatures. The cloud point of PEO in water exhibits a minimum as a function of surfactant concentration. We believe the minimum in the cloud point corresponds to a crossover from the noninteracting to the interacting regime.