Scalable manufacturing of layered nanoparticle-polymer composite films through evaporative assembly

This work explores stratification, a prescribed spatial variation of components in a multi-component film, in particle-polymer films prepared by a single-step evaporative drying technique. Our overall goal is to develop a more efficient and cost-effective way to create vertically structured multi-component polymer and colloid films. Films containing poly(acrylic acid) (PAA) chains and polystyrene (PS) colloidal nanoparticles were analyzed using microbeam small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM) to probe the impact of evaporation rates and colloid sizes on stratification behavior. Under slow drying conditions, particle-on-top stratification was observed, consistent with a diffusive model of stratification behavior. Conversely, moderate evaporation rates resulted in non-stratified configurations for certain mixtures. Fast evaporation, achieved by drying at elevated temperatures, induced polymer-on-top stratification, which aligns with predictions from simulations. Overall, this study proposes a more efficient method for creating vertically structured films, with implications for various industries.