Pore size design of ordered mesoporous silicas by controlling micellar properties of triblock copolymer EO20PO70EO20

The pore sizes of SBA-15 materials have been reduced continuously by controlling the micelle properties of block copolymer EO20PO70EO20 (P123) using the cationic surfactant cetyltrimethylammonium bromide (CTAB) as co-template, and the NH4F and KCl as inorganic additives. The resulting SBA-15 materials have been characterized by X-ray diffraction (XRD) patterns, N-2 physical sorption isotherms, and transmission electron microscopy (TEM). Experiments show that the pore sizes of SBA-15 decrease continuously from 8.49 nm to 4.78 nm with the increase of CTAB contents. However, the increase of CTAB contents results in lower structural ordering of the SBA-15 materials synthesized. The addition of F- dramatically improves the structural periodicity, but enlarges the pore sizes of the materials at the same time. In contrast, the introduction of KCl into the synthetic system can improve the structural ordering without evident effect on the pore sizes. It is suggested that the changes of micellar properties caused by the auxiliaries (CTAB, KCl, NH4F) should be responsible for the variation of the pore sizes of the resultant SBA-15. (c) 2005 Elsevier Inc. All rights reserved.