Spontaneous Formation of Hierarchical Macro-Mesoporous Ethane-Silica Monolith

Monolithic ethane-silica gels with well-defined cocontinuous macropores and highly ordered mesopores have been synthesized via a spontaneous route from silicon alkoxide with the aid of a structure-directing agent. While the macropores are formed by the concurrent phase separation and sol-gel transition induced by the polymerization reaction, the mesopores are templated by the self-organization of the structure-directing agent. Starting from a homogeneous mixture of the starting components, all the structure formation processes take place spontaneously in closed conditions at a constant temperature. Subsequent evaporation drying and heat treatment result in gels with hierarchical and fully accessible pores in discrete size ranges of micrometer and nanometer. While the local alignment of the mesopores is confirmed by FE-SEM observation, the long-range mesoscale order over the whole sample is evidenced by X-ray diffraction measurements. With the addition of a micelle-swelling agent, the mesostructural transition from 2D-hexagonal order to mesostructured cellular foam, MCF, has been observed without disturbing the macroporous framework structure