Development of Long Range Order in MCM-41

MCM-41 is largely an amorphous silicate. The small angle diffraction peaks arise from the repeat distances between the hexagonally close packed channel system, rather than from regular atomic repeat distances. The silica framework gives no Bragg peaks suggesting shorter-range order. The number of peaks in the diffraction pattern therefore reflects the degree of long-range order monodispersity and regular arrangement in the channel packing. The earliest published patterns show up to three peaks,1-3 however many published patterns show only the first order peak. Such materials have a very broad adsorption step in the nitrogen isotherms and TEM data show areas more reminiscent of Swiss cheese, than ordered honeycomb-like structures. Since the silicate walls of this material are not crystalline, the best strategy for improving the quality of the information from experimental data is to improve the long range order in the channel packing. This more uniform average structure would also make the interpretation of data from techniques which measure ‘bulk’ properties, such as X-ray and neutron scattering and gas adsorption isotherms, easier since smearing factors like polydispersity in channel dimension play a much smaller role in more ordered materials.