Poly(ethylene oxide)-sodium dodecyl sulfate interactions studied using static and dynamic light scattering

Abstract

Static and dynamic light scattering measurements have been made on poly(ethy1ene oxide) (PEO) in the presence of the ionic surfactant sodium dodecyl sulfate (SDS) in aqueous solution over a range of relative concentrations. The purpose was, in part, to demonstrate the polyelectrolyte effecte which arise in PEO on formation of the charged complex between the components in solution in which small SDS micelles are incorporated into the flexible PEO coil. The influence of the ionic strength of the medium was studied. Static light scattering measurements show that the radius of gyration changes as a function of SDS concentration and the ionic strength of the medium. Diffusion coefficients from dynamic light scattering (DLS) reflect changes in the pair interaction potential as the SDS and ionic strength are altered. Laplace inversion of the DLS time correlation function gives relaxation time distributions consisting of the PEO/SDS complex as the main component and free SDS micelles as the minor component. Changes in peak areas are related to the increase in the degree of binding between SDS and PEO as the relative concentrations change and also the increase in SDS micellar size with increase in the ionic strength of the medium.