The effect of alkan-1-ols addition on the structural ordering and morphology of mesoporous silicate MCM-41

The effects of adding alkan-1-ols to surfactant-silicate gels during the synthesis of mesoporous silica MCM-41 are reported. Upon adding an optimal amount of medium carbon chain length alkan-1-ols (CmH2m+1OH, CmOH; m greater than or equal to 4) to quaternary ammonium halides C(n)H(2n+1)TMAX (n = 10-14, C(n)TMAX, X = Br or Cl)-silicate systems, a marked improvement in the hexagonal order and the morphology of the synthesized MCM-41 materials was found. The optimal amount of added CmH2m+1OH for the formation of well ordered hexagonal structure was found to decease with increasing carbon chain length of the C(n)H(2n+1)TMAX surfactant and CmH2m+1OH. However, when an excessive amount of alcohol is added, the mesostructure obtained from the longer carbon chain length C(n)H(2n+1)TMAX-silicate (n greater than or equal to 12) systems becomes lamellar. The addition of CmOH (m greater than or equal to 4) offers a new synthetic approach to form lamellar-hexagonal liquid crystal intermediates necessary for synthesizing tubules-within-tubule (TWT) hierarchical structures whose morphology and size can be controlled by varying the water content and the CmH2m+1OH/surfactant ratio.