Simple synthesis of hierarchically structured silicas by poly(ethyleneimine) aggregates pre-organized by media modulation

In this paper, we describe the multiple morphogenesis of poly(ethyleneimine) (PET)-directed silicas through the facile tuning of the media in which the PEIs pre-organize. The silica shapes and structures ranged from nanofiber-based asters, fans, particles, plates, and/or curved films to large aggregates composed of unit nanoribbon structures and networks that contained nanospheres or particles, depending on the media compositions or media modulations coupled with the polymer concentrations and chain architectures. We found that the media modulations not only controlled the formation of the silica unit structures but also manipulated the hierarchical structures based on the unit silicas. Furthermore, methanol modulation successfully allows us to elucidate the dependence of silica deposition ability on the polymer chain architectures that cause subtle differences in their aggregates. The approach of methanol modulation to obtain shaped silicas, which involves both PEI aggregation and silica deposition at room temperature, is of particular interest to applications for the immobilization of bioactive components.