Effect of polymer-to-silica ratio on the formation of large three-dimensional cage-like mesostructures

This work shows the influence of polymer-to-silica ratio on the formation of cage-like ordered mesoporous silica, FDU1, having a three-dimensional face-centered cubic symmetry. The FDU1 samples studied were synthesized from tetraethyl orthosilicate (TEOS) under acidic conditions in the presence of poly(ethylene oxide)-poly(butylene oxide)-poly(ethylene oxide) (EO39BO47EO39) triblock copolymer. The molar ratio of triblock copolymer to TEOS in the reaction mixture was varied from 0.0037 to 0.0148. Small angle X-ray scattering, argon adsorption-desorption and high resolution thermogravimetry studies indicate that an optimal EO39BO47EO39/TEOS ratio, which led to a high-quality FDU1 material with uniform cage openings, narrow pore size distribution and high specific surface area, was about 0.0074. The FDU1 silicas obtained for lower and higher ratios than the aforementioned value possessed non-uniform cage entrances, broader pore size distributions, lower BET specific surface areas and smaller mesopore diameters.