The viscosity of polymer–surfactant mixtures in water

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Abstract
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.