(647d) Organizing Inorganic Nanoparticles into Microcapsules Using Polymer Aggregates

With the recent advances made in solution-phase materials chemistry, nanoparticles (NPs) can now be prepared out of a wide spectrum of compositions with a high degree of particle size and shape control. NPs are an intriguing class of materials because their reduced physical dimensionality leads to the appearance of catalytic, chemical, optoelectronic, and magnetic properties not found in bulk materials. They remain rather difficult to handle for applications, though, due to their colloidal nature and their susceptibility to uncontrolled aggregation. In this talk, I will discuss our successful efforts to induce and understand the controlled assembly of microcapsule structures out of NPs and polymers. The polyelectrolyte (e.g., polyallylamine) forms aggregates under the crosslinking action of a multivalent salt (e.g., EDTA). These aggregates essentially act as templates around which the NPs deposit to form a multilayer-thick NP/polymer shell. We term this form of NP assembly as "polymer aggregate templating" and the resultant nanoparticle-assembled capsules as "NACs." The synthesis conditions (room temperature, atmospheric pressure, near-neutral pH, water solvent, rapid formation) allow water-soluble compounds to be encapsulated easily and without damage, and the microcapsule formation process to be potentially scaled up. I will describe some of the materials properties that point to applications in encapsulation, delivery, and controlled release.