Preparation of mesoporous silica particles with controlled morphology from sodium silicate solutions and a non-ionic surfactant at pH values between 2 and 6

Isometric particles of mesoporous silica could be synthesized between 25 degrees C and 45 degrees C from reaction mixtures containing silicic acids, sodium chloride and a non-ionic surfactant (Triton X100), The size decreases from some tens of micrometers to less than 1 mu m when the pH increases from 1.85 to 6. At pH lower than 3.5, glassy material forms a cement between the particles. The particle size distribution narrows at higher pH and at long reaction times (several days). A spheroidal shape is favored by low pH and high temperature, and a more polyhedral shape appears at high pH whatever the temperature, This behavior could be related to the polycondensation rate of the silicic acids, to the lifetime and disorder of the micelles and to the micelles-silicic acid interactions. (C) 2000 Elsevier Science B.V. All rights reserved.