Intrinsically Superhydrophobic Organosilica Sol−Gel Foams

Abstract

Intrinsically superhydrophobic foams with contact angles greater than 150° were prepared using a sol−gel phase-separation process. Hydrophobicity was built in by using organofunctionalized inorganic monomers and setting the conditions so that they were retained in the product. The materials were characterized by advancing and receding water contact angle measurements, scanning electron microscopy, and infrared spectroscopy. The sol−gel phase-separation preparation method used was simple and produced roughness and hydrophobicity in the same material, thus obviating the need for a hydrophobic coating to achieve superhydrophobicity. Superhydrophobicity was retained when the materials were cut or abraded. On heating, a rapid hydrophobic to hydrophilic transition was present at around 400 °C, generating a material that absorbed water rapidly. “Flat” sol−gel materials prepared without phase separation treated in the same manner showed a more gradual contact angle change, but the switch from hydrophobicity to hydrophilicity also occurred at around 400 °C.