Manipulating Interfacial Polymer Structures through Mixed Surfactant Adsorption and Complexation

The effects of a nonionic alcohol ethoxylate surfactant, C13E7, on the interactions between PVP and SDS both in the bulk and at the silica nanoparticle interface are studied by photon correlation spectroscopy, solvent relaxation NMR, SANS, and optical reflectometry. Our results confirmed that, in the absence of SDS, C13E7 and PVP are noninteracting, while SDS interacts strongly both with PVP and C13B7. Studying interfacial interactions showed that the interfacial interactions of PVP with silica can be manipulated by varying the amounts of SDS and C13B7 present. Upon SDS addition, the adsorbed layer thickness of PVP on silica increases due to Coulombic repulsion between micelles in the polymer layer. When C13E7 is progressively added to the system, it forms mixed micelles with the complexed SDS, reducing the total charge per micelle and thus reducing the repulsion between micelle and the silica surface that would otherwise cause the PVP to desorb. This causes the amount of adsorbed polymer to increase with C13E7 addition for the systems containing SDS, demonstrating that addition of C13E7 hinders the SDS-mediated desorption of an adsorbed PVP layer.