TEMPLATING OF MESOPOROUS MOLECULAR-SIEVES BY NONIONIC POLYETHYLENE OXIDE SURFACTANTS

Mesoporous silica molecular sieves have been prepared by the hydrolysi s of tetraethylorthosilicate in the presence of low-cost, nontoxic, an d biodegradable polyethylene oxide (PEG) surfactants, which act as the structure-directing (templating) agents. This nonionic, surfactant-ne utral, inorganic-precursor templating pathway to mesostructures uses h ydrogen bonding interactions between the hydrophilic surfaces of flexi ble rod- or worm-like micelles and Si(OC2H5)(4-x)(OH)(x) hydrolysis pr oducts to assemble an inorganic oxide framework. Disordered channel st ructures with uniform diameters ranging from 2.0 to 5.8 nanometers hav e been obtained by varying the size and structure of the surfactant mo lecules. Metal-substituted silica and pure alumina mesostructures have also been prepared by the hydrolysis of the corresponding alkoxides i n the presence of PEO surfactants. These results suggest that nonionic templating may provide a general pathway for the preparation of mesop orous oxides.