Preparation of flexible, hydrophobic, and oleophilic silica aerogels based on a methyltriethoxysilane precursor

We report the synthesis of flexible, hydrophobic, and oleophilic silica aerogels through a two-step acid-base sol-gel reaction followed by supercritical drying, in which methyltriethoxysilane (MTES) is used as a precursor, ethanol (EtOH) as a solvent, and hydrochloric acid (HCl) and ammonia (NH3 center dot H2O) as catalysts. At the optimal molar ratio of MTES:EtOH:H2O:HCl:NH3 center dot H2O is 1:18:3.5:1.44 x 10(-4):1.2, MTES-based silica aerogels show the minimum density of 0.046 g/cm(3) and the maximum compression ratio of 80 % with 15.09 kPa stress. They are superhydrophobic with a water contact angle of 157A degrees and thermally stable up to 350 A degrees C. We also find that they show the excellent adsorption for ethanol with a ratio of 1400 %.