Long-range ordered lyotropic liquid crystals in intermediate-range ordered protic ionic liquid used as templates for hierarchically porous silica

Abstract

An approach to prepare hierarchically nanostructured silica materials possessing both micro- and mesoporosity has been investigated. Tetramethoxysilane was hydrolysed in the long-range ordered lyotropic liquid crystal (LLC) phase formed from the non-ionic block copolymer Pluronic P123 in the intermediate-range ordered protic ionic liquid (PIL), ethylammonium nitrate (EAN). The structures of the silica materials prepared with various amounts of inorganic precursor were characterized by using small angle X-ray scattering, N₂ gas sorption, and TEM. The final silica materials contained a disordered population of micropores coexisting with an ordered population of mesopores with an average pore size of 1.0 nm and 4.5 nm respectively. The bimodal nanoscale pore structure reflects the nanostructure of the EAN PIL and that of the P123-EAN LLC phase, respectively. The specific surface area of the micro/mesoporous silica ranged from 485 to 949 m²g⁻¹, depending on the inorganic precursor concentration.