A systematic investigation of the formation of ordered mesoporous silicas using poly(ethylene oxide)-b-poly(methyl methacrylate) as the template

Two different approaches, the conventional solvent evaporation induced self-assembly (EISA) and the novel solvent evaporation induced aggregating assembly (EIAA), were employed to synthesize ordered mesoporous silicas (OMSs), respectively, by using amphiphilic diblock copolymer poly(ethylene oxide)-b-poly(methyl methacrylate) as the template, with an aim to systematically investigate the difference of the two approaches and their effect on the textural properties of the obtained porous materials. The mesoporous silicas synthesized via the two methods possess face centered cubic (fcc) mesostructure, large pore size and high surface area. However, compared with the OMSs with a film-like morphology from EISA, the OMSs from the EIAA have a particle-like morphology, thinner pore wall and higher surface area, which is favorable for their applications. More importantly, the novel EIAA process is more versatile and can be used to synthesize ordered mesoporous silicas and silica-based nanostructured materials with different morphologies. By introducing ethanol as the additive in the EIAA system, unique mesoporous silica spheres with a diameter of 1-5 μm, large pore size (∼16.8 nm), huge window size (∼8.9 nm), and high surface area (∼482 m² g ^-1) can be synthesized. Through increasing the content of water, uniform silica hollow spheres (20-40 nm in diameter) and silica nanotubes (diameter ∼30 nm) can be obtained by using templates with higher and lower molecular weight, respectively.