Surfactant/Polymer Assemblies. 1. Surfactant Binding Properties

The binding characteristics of aggregates formed between neutral polymer (PVP) and anionic surfactant (SDS) are explored by light scattering. As added SDS binds to PVP polymers, the mass increase of the scattering aggregates is reflected in higher scattered intensity, so long as electrostatic interactions due to the SDS charge (as reflected in the second virial coefficient, A 2) are suppressed by high ionic strength. Although there is an equilibrium between bound and free SDS, the majority of the scattering observed is due to SDS/PVP aggregates. These aggregates appear to consist of single PVP polymer chains with multiple bound SDS micelle-type structures. Attempts are made to quantify the binding of SDS to PVP in terms of the binding energy and binding volume, using both a model of scattering from multicomponent systems and a model of the thermodynamics of the binding process. Additionally, the saturation of PVP with SDS allows us to determine the stoichiometry of the SDS/PVP aggregation and suggest a physical cause for the saturation.