Search

Graphical abstract Highlights • Sustainable preparation of mesoporous silica. • ScCO 2 extraction of non-ionic templates. • Fast extraction of the organic template. • Improvement of material crystallinity. • Hydrothermal resistance of mesoporous silica. Abstract We report how we could circumvent two major drawbacks in the potential scale up synthesis of mesoporous silica via the surfactant-based templating route. First, burning the organic templates to free porosity is costly and not environmental friendly. Most of the mesoporous silica materials show also extremely poor resistance to hydrothermal environments. These drawbacks have certainly contributed to prevent these materials meet practical use, and hampered any possible large-scale manufacturing. Unlike previous reports that claimed that supercritical carbon dioxide (scCO 2) was ineffective in removing most of the organic templates, except amines, we describe how the unique synergy we achieved between scCO 2 extraction and our two-step synthesis of mesoporous silica with nonionic templates allowed us to overcome these drawbacks. We conducted different tests, and we report here the preparation of mesoporous materials with tunable pore size between 1 and 10 nm, structure varying from 3D wormhole to hexagonal, and hydrothermal resistance. [ABSTRACT FROM AUTHOR]

We report how the control of a single parameter, the co-surfactant, determines the phase transitions of oil-in-water swollen liquid crystals (SLCs) prepared with cetyltrimethylammonium bromide (CTAB), from cubic to hexagonal, lamellar, and finally sponge-like structures. SLCs are complex mixtures (surfactant + co-surfactant + water + salt + oil) usually prepared to form hexagonal mesophases, with cell parameters tunable between 3 and 30 nm. These hexagonal mesophases were successfully used as nanoreactors to prepare a broad range of nanostructured materials. Because the potential of these mesophases as adaptive nanoreactors has not been extended to other liquid crystal geometries than the hexagonal, we studied in a first step the structure evolution of SLCs made with CTAB, cyclohexane, pentanol-1, water and different stabilising salts. We used small-angle X-ray scattering (SAXS), polarised light microscopy and Freeze-Fracture TEM to provide a partial phase diagram and list the different mesophases obtained as a function of composition. We report that the adjustment of a single parameter, the co-surfactant (pentanol-1), determines the phase transition between cubic, hexagonal, lamellar, and sponge-like structures, all other parameters such as the nature and concentration of salt, or amount of oil being constant. [ABSTRACT FROM AUTHOR]