Fabrication of hierarchically ordered porous films composed of imogolite via colloidal templating

Hierarchically ordered porous materials composed of imogolite with macro-, meso- and microporous systems were fabricated via colloidal templating. The monodispersed polystyrene particles used as templates were assembled into a close-packed structure on Si substrates. An imogolite sol was infiltrated into voids of polystyrene particles to form composite films. The ordered macropores as well as micro- and mesopores originating from imogolite were confirmed after the removal of templates by either extraction with toluene or calcination. The films were stable in organic solvents, such as acetone, ethanol, and hexane. Although the extracted film was unstable in water, the stability was improved by calcination. Imogolite is found to be a quite useful building block to fabricate hierarchically ordered porous materials with a wide range of porosities without using surfactants as templates.