MCM-41 mesophase

Fowler C. E., Lebeau B. and Mann S. Covalent coupling of an organic chromophore into fictionalized MCM-41 mesophases by template-directed co-condensation, Chem. Commun. (1998) pp. 1825-1826. 

Figure 9.1 Examples of texture of the materials formed on a short range from amorphous Si02 (a) silica gel (b) hydrothermally treated silica gel (c) porous glass (d) mesoporous mesophases type of MCM-41 and (e) opal.

The synthesis of MCM-41 structure in fluoride medium has been reported by Silva and Pastore [10], who used sodium silicate as silica source and carried out crystallization at 150 °C. They suggested the behaviour of Si02-CTMA+-F system was significantly different from that reported previously on the mesophase system. It is known that fluoride ions do influence the nature, activity and polymerizing capacity of silica precursors, and a fluorinated silica surface is much more hydrophobic and more resistant to the attack of water molecules than a silanol silica surface [11]. 

S. R. Hall, C. E. Fowler, B. Lebeau, and S. Mann, Template-directed synthesis of bi-fimctionalized organo-MCM-41 and phenyl-MCM-48 silica mesophases, Chem. Commun. 201-202 (1999). 

Calculated from the equation unit cell parameter = mesopore diameter + wall thickness. Mesoporous mesophase material of the MCM-41 type. 

Other factors that affect the structure of mesophases include the concentration ratio between surfactants and inorganic precursors. For example, MCM-41 was prepared at a Ci6H33(CH3)3N+/Si ratio of less than 1. As the Ci6H33(CH3)3N+ /Si ratio increases beyond 1, the cubic phase (Ia3d) can be produced. Similarly, Nb-TMSl (/ 6m), Nb-TMS2 (E63/WWC), Nb-TMS3 (Pm-3n), and Nb-TMS4 (p2) were prepared at various surfactant to Nb ratios. ... 

Powder x-ray diffraction data of Ru-MCM 41 show a dioo peak at 3.7° on 20 scale, which confirms the hexagonal phase is formed. The powder x-ray diffraction analysis performed on the sample after heat-treatment confirmed that the material retains the hexagonal symmetry of the mesophase. 

Mesostructure syntheses can be carried out under conditions in which the silicate alone would not condense to solid (at pH 12 14 and low silicate concentration) and the surfactant CTAB (concentration < 2%) alone would not form a lyotropic liquid-crystal phase. The rapid formation of MCM-41 when surfactant solution and silicate solution are combined indicates that there is strong interaction between the cationic surfactant and anionic silicate species in the formation of mesophases. 

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