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| - A Mechanistic Study of the Formation of Mesoporous Structures fromin Situ AC Conductivity Measurements
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| - The purpose of this work is to study the kinetics of self-assembly in the formation mechanism of anionic templatedmesoporous solids (AMS-n) during the first few seconds of the synthesis as well as to demonstrate the use of alternatingion current (AIC) conductivity measurements to follow the self-assembly in complex hybrid systems. The formationof different AMS-n caged-type mesostructures through the delayed addition of the silica source is demonstrated andexplained in terms of the interaction between the co-structure-directing agent (CSDA) and the oppositely chargedsurfactant headgroup regions. Our findings, supported by transmission electron microscopy, 29Si magic angle spinningnuclear magnetic resonance (MAS NMR) spectroscopy, dynamic light scattering (DLS) measurements, and powderX-ray diffraction suggest that the interaction of the CSDA with the surfactant headgroup occurs within seconds afterits addition to the synthesis gel leading to interaction between the polymerizing CSDAs and the oppositely chargedmicelle and to an increase in the micelle-CSDA aggregate size. Both DLS and AIC measurements agree that thisprocess occurs within the first 1000 s after addition of the CSDA to the synthesis gel at room temperature. In additionto the mechanistic study it was found that the intermediate materials are comprised of a three-layer entity. Time-dependent 29Si MAS NMR studies reveal that an organo-silica layer forms around the micelles prior to a condensedouter inorganic shell of silica.
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