Controlling thickness in hexagonal polymer templated mesoporous silica films

Many templated mesoporous silica films are synthesized through a solution phase co-assembly process involving association of surfactants or block-copolymers with silica precursors that is driven by the evaporation of solvent. During the film formation, a liquid crystal type structure with well-defined nanometer scale periodicity is formed and then made rigid by condensation of the silica precursors. For a variety of applications there is an interest in controlling the film thickness. The objective of this investigation is to find systematic rules that determine film thickness in hexagonal SBA-15 type silica/polymer composite materials. We find that despite the complex self-organization in these materials, all thickness data can be fit with classic models for evaporation induced deposition in dip-coated films. The models relate film thickness, pull rate, solution viscosity, and solution density. The thickness data can be modeled with no adjustable parameters over more than an order of magnitude thickness range.