(82b) Exploiting Self Assembly and Phase Separation to Produce Multiscale Porous Architectures in Particles Made by Aerosol Routes

Phase segregation between polymer and gelling silica has been utilized to introduce a controlled second level of porosity into mesoporous silica particles produced by evaporation-induced self assembly (EISA) of aerosols. During EISA within aerosol droplets, solvent evaporation leads to surfactant self assembly, which introduces ordered mesoscale (2?10 nm) porosity (after surfactant removal) into a silica matrix. Evaporation of droplets that also include a hydrophilic polymer such as polyacrylic acid results in polymer phase separation that, after organic removal, introduces larger voids (10-100 nm) in addition to the mesoporosity provided by the surfactant self-assembly. The incorporation of the polymer does not interfere with the surfactant self assembly or the resulting mesoscale porosity up to rather high levels of polymer loading. Variation of experimental parameters and conditions, such as the concentration of the polymer, solvent composition, and molecular weights of the polymer, can be used to influence the structure and scale of polymer-derived voids within the particles, allowing the synthesis of single central voids (hollow particles) or uniformly dispersed smaller voids. Such particles have intriguing potential as controlled release or delivery vehicles and sensing platforms. Synthetic routes and results will be described, as well as a qualitative overview of our current understanding of the various dynamic EISA processes that influence particle architecture.