| Abstract
| - The effect of processing mesoporous silica thin films with supercritical CO2 immediately after castingis investigated, with a goal of using the penetration of CO2 molecules in the tails of fluorinated surfactanttemplates to tailor the final pore size. Well-ordered films with two-dimensional hexagonal close-packedpore structure are synthesized using a cationic fluorinated surfactant, 1-(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl)pyridinium chloride, as a templating agent. Hexagonal mesopore structuresare obtained for both unprocessed films and after processing the cast films in CO2 at constant pressure(69−172 bar) and temperature (25−45 °C) for 72 h, followed by traditional heat treatment steps. X-raydiffraction and transmission electron microscopy analysis reveal significant increases in pore size for allCO2-treated thin films (final pore diameter up to 4.22 ± 0.14 nm) relative to the unprocessed sample (finalpore diameter of 2.21 ± 0.20 nm) before surfactant extraction. Similar pore sizes are obtained with liquidand supercritical fluid treatments over the range of conditions tested. These results demonstrate thatcombining the tunable solvent strength of compressed and supercritical CO2 with the “CO2-philic” natureof fluorinated tails allows one to use CO2 processing to control the pore size in ordered mesoporous silicafilms.
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