Trimethylsilyl substituent modification of silica aerogels

Low-density hydrophobic silica aerogels were produced by modification of conventional silica aerogels via substitution of －OH groups by trimethylsilyls. IR spectra and thermogravimeturic anglyses were to characterize the aerogels before and after modification, And the diameter changes of modified and unmodified aerogel micro cylinders were tracked using a measuring microscope. The results show that the hydrophobic silica aerogels possess much higher stability than hydrophilic ones due to the diminishment of －OH groups and the radial shrinkage ratio of cylinder samples decreases dramatically from 30% down to 3% after modification．