Polyaniline nanofiber-silica composite aerogels

Strong, electrically conducting aerogels were prepared by introducing polyaniline nanofibers to a silica sol just prior to gelation and drying through supercritical carbon dioxide processing. The addition of a few milligrams of polyaniline per cm ³ increased the flexural strength of the cylindrical monoliths by 200%. Using preformed polymeric nanofibers avoided filling of microporosity often observed with polymer reinforcement of aerogels and allowed preparation of polyaniline-silica composite aerogels with surface areas over 900 m ²/g. Despite the small amount of polyaniline nanofibers (1.3-16.5 wt.%), the composite aerogels were electrically conducting (8.0 × 10 ^{- 8}-1.83 × 10 ^{- 5} S/cm) and it was possible to prepare chemiresistor sensors for detection of acidic (HCl) and basic (ammonia) gaseous molecules with response times similar to thin film sensors containing orders of magnitude more polyaniline.