STRUCTURE-PROPERTY RELATIONSHIPS IN THIN-FILMS AND MEMBRANES

The molecular-scale species distributions and intermediate-scale structure of silicate sols influence the microstructures of the corresponding thin films prepared by dip-coating. Using multi-step hydrolysis procedures, we find that, depending on the sequence and timing of the successive steps, the species distributions (determined by Si-29 NMR) and intermediate scale structure (determined by SAXS) can change remarkably for sols prepared with the same nominal composition. During film formation, these kinetic effects cause differences in the efficiency of packing of the silicate species, leading to thin film structures with different porosities.