STRUCTURE-PROPERTY RELATIONSHIPS IN THIN-FILMS AND MEMBRANES

The molecular-scale species distributions and intermediate-scale struc ture of silicate sols influence the microstructures of the correspondi ng thin films prepared by dip-coating. Using multi-step hydrolysis pro cedures, we find that, depending on the sequence and timing of the suc cessive steps, the species distributions (determined by Si-29 NMR) and intermediate scale structure (determined by SAXS) can change remarkab ly for sols prepared with the same nominal composition. During film fo rmation, these kinetic effects cause differences in the efficiency of packing of the silicate species, leading to thin film structures with different porosities.