Sol–gel process and complex fluids: sculpting porous matter at various lengths scales towards the Si(HIPE), Si(PHIPE), and SBA-15-Si(HIPE) series

Abstract

Taking inspiration from diatom hierarchically organized porosity, synthetic porous monoliths have been synthesized through rational designs while combining sol–gel chemistry, emulsions, Pickering-based emulsions, and lyotropic mesophases. We have described the synthesis of the Si(HIPE) series employing traditional emulsions to tune the macroscopic void diameters and cationic surfactant molecules to both stabilize the oil/water interface at the macroscopic length scale and create vermicular poorly organized porosity at the mesoscopic length scale. In a second part, while substituting surfactant molecules with modified silica nanoparticles acting as emulsion-stabilizers, we depict the possibility of tuning independently the macroscopic cell diameters and the cell junctions via Pickering emulsions employed as templates, leading to the Si(PHIPE) series presenting both monodiperse macroscopic void and cell junction diameters. Finally taking the synergetic effect of nonionic surfactants and a kosmotrope salt effect we show that it is possible generating self-standing Si(HIPE) bearing high organized mesoporosity while addressing the SBA-15-Si(HIPE) series.