Facile One-Pot Synthesis of Mechanically Robust Biopolymer–Silica Nanocomposite Aerogel by Cogelation of Silicic Acid with Chitosan in Aqueous Media

A sustainable aqueous-based route is reported for the synthesis of low density mesoporous silica/chitosan nanocomposite aerogels by cogelation of a chitosan biopolymer dissolved in silicic acid. The random “cluster–cluster” aggregate silica structure intertwined at the molecular level with chitosan yields a three-dimensional semi-interpenetrating network with greatly improved mechanical properties when compared to a silica aerogel of similar density. The physical properties of the resulting aerogels depend significantly on the gelation pH. A silica aerogel reference material synthesized at a low pH of 3 features very low density and high porosity resulting in a highly elastic behavior but comparatively weak skeletal structure (final strength 80%) but with greatly increased yield strength (>7 MPa). Importantly, the rein...