IN-SITU ATR FTIR STUDY OF MESOPOROUS SILICATE SYNTHESES/

Real time, in situ ATR/FTIR monitoring of M41S-type mesoporous silicat e syntheses were performed which enabled the observation of simultaneo us changes in both the organic and inorganic phases of the reaction mi xtures. The spectra are dominated by incompletely polymerized, surfact ant/silicate composites which form in the solution and/or gel phases, and coexist with the precipitated solid product. The majority of the o bserved spectral changes take place during the initial heat up stage o f the syntheses. The hydrocarbon tail section of the surfactant exhibi ts increasing packing disorder as the temperature rises. Increased hea dgroup ordering is observed during the M41S formation which can be att ributed to silicate anionic exchange with hydroxide ions, and the expu lsion of water of hydration from the headgroup region as condensation of the encapsulating inorganic sheath proceeds. Using a gel compositio n which generates the D4R cubic octomer, Si8O208- species, the strong surfactant ordering ability of this polyanion is seen in the early sta ges of the synthesis. The rapid decomposition of this silicate species is accompanied by a sudden increase in the packing disorder of the hy drophobic region of the micelle. These results illustrate the great ut ility of in situ ATR/FTIR in probing the synergies of this dual phase system.