Thermal treatments before and after precipitation during the synthesis of SBA-15 materials were studied. It was found that thermal treatments in a range of 28-55 degrees C during the first 10 min of TEOS polymerization had an effect on surface silanol groups and the amount of microporosity in the final SBA-15 materials. FTIR analysis of these obtained SBA-15 materials indicates that a change in the distribution of the type of surface silanol groups when the initial reaction temperature is raised to 55 degrees C occurs. The total pore volume was found to decrease with the increase of temperature which exhibits a decrease in microporosity. Post-synthesis grafting to replace silanol groups by OSi(CH3)(3) groups was used as a micropore blocking device. This method seems to reply more realistically to the experimental results as compared to the as plot method. (C) 2007 Published by Elsevier B.V.