Superhydrophobic and Flexible Aerogels and Xerogels Derived from Organosilane Precursors

The field of organosilane-derived aerogels is a rather young area of aerogel research. Inherently, organosilane precursors offer the advantage that they already contain at least one direct Si-C bond in the silane precursor, thus imparting specific chemical functionality. In particular, if used exclusively to prepare organo-modified polysiloxane aerogels, hydrophobicity originating from the organic substituent group(s) can bypass the need for a second post-modification (hydrophobization) step. Pioneered by early works, recent years have brought tremendous improvements in terms of methodology; combination with organic, hybrid (polymerization-based) chemistries, as well as ambient-drying protocols. Modern organosilane-based preparation techniques are cost-competitive with conventional silica aerogel synthetic routes but offer a tremendous added value potential through the use of suitable “secondary functionalization” protocols, particularly obvious in many examples in the form of improved mechanical properties (bendability, machinability, higher toughness, and e-modulus) but also improved resistance against organic solvents. This chapter gives an overview over this trendsetting and commercially promising field of aerogels, a discussion on potential applications, as well as an outlook and brief analysis of the key challenges ahead.