Colloidal and interfacial phenomena in polymer/surfactant mixtures

In this dissertation, I explore the multicomponent effects that arise in mixtures of an amphiphilic triblock copolymer, Pluronic F108, and an anionic surfactant, sodium dodecylsulfate (SDS). In solution, Pluronic F108 and SDS can bind cooperatively, resulting in a polymer surfactant complex with some polyelectrolyte characteristics. Using a pyrene solubilization assay I identify the surfactant concentration regimes where different F108/SDS aggregates form in bulk solution at several ionic strengths.; Using optical reflectometry I find that the F108/SDS complexes show unique adsorption characteristics, including a surfactant shuttling effect whereby the anionic SDS is carried by the surface-active Pluronic F108 to negatively charged silica surfaces. I find that the coadsorbed amount is extremely sensitive to the concentration of SDS.; To probe the thickness of the “unprocessed” and SDS “processed” adsorbed layers I use an electrokinetic technique. Streaming current and streaming potential methods provide a measurement of the hydrodynamic thickness of Pluronic F108 layers. I find that SDS “processed” layers are thinner than “unprocessed layers”.; To confirm this measurement of thickness and to measure the steric interactions caused by adsorbed Pluronic F108, I perform several Atomic Force Microscopy (AFM) measurements. These measurements confirm that the layer is thinned by SDS “processing”. This thinning can be explained by the ability of the SDS to spatially “condense” a Pluronic F108 chain at low SDS concentration.; I use Total Internal Reflection Microscopy (TIRM) to probe the colloidal forces caused by the formation of polyelectrolyte-like polymer/surfactant complexes. A tunable depletion attraction arises when SDS is present in F108 solutions at a concentration higher than the critical aggregation concentration (cac). This depletion interaction is highly sensitive to polymer concentration, surfactant concentration and salt concentration.; Finally, I perform a study of the stability of silica suspensions in the presence of Pluronic F108 and SDS mixtures as well as each component individually. There are several SDS and salt concentrations where suspension stability is observed only in the presence of Pluronic F108. Pluronic F108 alone at these salt concentrations does not stabilize the suspensions. (Abstract shortened by UMI.)...