Comparison of adsorption properties of MCM-41 materials obtained using cationic surfactants with octyl chain

Adsorption properties of the MCM-41 material synthesized by using octyltrimethylammonium bromide are compared with those for two analogous samples reported previously. One of them was also obtained by using octyltrimethylammonium bromide, whereas the other one was prepared by employing judiciously selected mixtures of double-chain octylammonium surfactants. These samples were characterized by powder X-ray diffraction and nitrogen adsorption. While the average size of primary mesopores is about 2.3 nm for the aforementioned samples, their specific surface areas and pore volumes show more pronounced differences depending on the synthesis conditions. It is shown that the usage of the mixture of double-chain octylammonium surfactants of a proper composition lead to the best quality MCM-41 samples. Moreover, this work indicates that the good quality MCM-41 samples can be also obtained for surfactants with single octyl chain if the synthesis conditions are properly selected. For instance, this can be achieved by extending the time of hydrothermal treatment of the silica-surfactant mesostructures. (C) 2002 Elsevier Science B.V. All rights reserved.