Non-supercritical drying sol–gel preparation of superhydrophobic aerogel ORMOSIL thin films with controlled refractive index

Abstract

Superhydrophobic aerogel ORMOSIL (organically modified silicate) thin films with controlled refractive index were prepared by a one-pot sol–gel process without supercritical drying. The method involved the preparation of ORMOSIL particles by co-condensation of tetramethylorthosilicate (TEOS) and dimethyldiethoxysilane (DDS) and a further surface modification of ORMOSIL particles with hexamethylsilazane. The particle growth process of ORMOSIL sols and the drying process of aerogel ORMOSIL thin film are discussed in detail. The co-condensation of TEOS and DDS and the surface modification significantly improved the hydrophobicity and hence the environmental resistance of the thin films; the water contact angles of the thin films increased from 23° to 151°. A superhydrophobic aerogel ORMOSIL thin film with refractive index as low as 1.10 was obtained. In addition, the refractive indices can be tailored in the range of 1.10–1.23. Superhydrophobic aerogel ORMOSIL (organically modified silicate) thin films with controlled refractive index were prepared by sol–gel process without supercritical drying.