(468d) Assembly of Nanoparticle-Polyelectrolyte Membranes at Water-Water Interfaces

We study the formation of structures at water-water interfaces. Assembly at water-water interfaces differs significantly from the more typical setting of interfaces between immiscible fluids of differing polarity. On these more typical interfaces, molecules and particles readily assemble to reduce the high interfacial tensions or surface energies that are absent in our system. Water-water interfaces are particularly powerful scaffolds owing to the mild solution conditions and the fact that the interface is in contact with the two adjacent water phases. Such an open scaffold is able to accept material from both bulk phases. We have fabricated membrane-like structures at these interfaces with interesting structures and transport properties. We study assembly of polyelectrolytes (PEs) and nanoparticles (NPs) at an interface between two aqueous phases formed from polyethylene glycol (PEG) and dextran. Motivated by the analogies and differences between our system and layer-by-layer (LbL) assembly of NPs and PEs, we explore the importance of osmotic stress imbalances and the presence of salts in regulating the membrane structure and rate of growth to gain mechanistic insight into structure formation.