Hierarchical self-assembly of colloidal nanoplatelets driven by evaporation

Abstract

Driven colloids are out of equilibrium systems, which self-organise into diverse complex structures, and have been one of the major driving themes in materials science. We report experimental studies on the evaporation driven self-assembly of colloidal nanoplatelets of montmorillonite and laponite. The sol-gel transition is studied using a rheometer and imaging by confocal laser scanning fluorescence microscope and an electron microscope to probe the microstructures. Evaporation driven thin films prepared from the bicontinuous gel state show increasing transparency and decreasing surface roughness with increasing concentration of laponite. Polarising optical microscope shows a microstructure with string-like birefringent domains. The scanning electron microscope reveals nacre-like structure of the films and decreasing inter-layer spacing with increasing concentration of laponite. The composite films showed superior flame-shielding property compared to the films made of individual components.