Sol-gel derived porous silica films

A modified sol-gel process, involving gelation of drops of a starting solut ion pressed on a substrate by a non-wetting glass, has been employed to obt ain porous silica coatings on glass substrates at room temperature and pres sure. Deposited films are homogeneous and crack-free. Films having a thickn ess higher than 5 mu m can be obtained. These aerogel like coatings show a refractive index lower than 1.2 and a dielectric constant lower than 2 with a pore volume of about 60%. Films exhibit hydrophobic properties because o f surface modification. (C) 1999 Elsevier Science B.V. All rights reserved.