Synthesis and characterization by FTIR spectroscopy of silica aerogels prepared using several Si(OR)4 and R"Si(OR′)3 precursors

We report the synthesis and Fourier Transform Infrared spectroscopy characterization results dealing with the surface modification of silica aerogels obtained via a two-step sol-gel process where various silicon precursors and co-precursors were used. The hydrolysis and poly-condensation steps were followed by carbon dioxide supercritical drying (T-c = 31.1 degrees C; P-c = 73.7 bar). The silicon precursors contain four identical hydrolysable alkoxy groups (methoxy or ethoxy). while in the co-precursors, one of the alkoxy groups is substituted by a non-hydrolysable alkyl group (methyl, ethyl, n-propyl, iso-butyl, n-octyl, vinyl or phenyl). Identically, surface-functionalized silica aerogels were obtained from various silicon precutsor/co-precursor combinations and their chemical structures were compared. The infrared spectroscopy revealed the existence of chemically comparable solid networks with some differences due to the nature of the silicon precursors. (c) 2008 Elsevier B.V. All rights reserved.