Nanoparticle-Decorated Honeycomb-Structured Polymeric Films Via Breath Figures with Janus Particles

Microporous polymer scaffolds decorated with nanoparticles could provide functional membranes that are needed in solar-to-fuel technologies. Therefore, efficient production processes are needed for high surface area, porous membranes with distinct catalytic nanoparticles on opposite sides of a support that resists oxidation and separates the products, e.g., hydrogen and oxygen. Breath figure (BF) patterning is an established method to create microstructured honeycomb-patterned porous polymer films. This research shows that surface-active nanoparticles can self-assemble onto the interfaces between the templating BF water droplets and the polymer solution to control micrometer and nanometer-scale hierarchical structure. Here, amphiphilic “Janus” nanoparticles serve as both solid surfactants and Pickering emulsion stabilizing agents, thus able to optimize ordering degree of the honeycomb structures and nanoparticle enrichment in the pore walls. Janus nanoparticles were synthesized using literature methods (with improvements that will be presented): functionalizing only the exposed surface of particles embedded on the surface of wax microspheres (colloidosomes) renders half of the particle hydrophobic. They were then employed in the BFs templating method for the first time, resulting in regular, porous films with uniform, high nanoparticle density. Humble materials (silica and polystyrene) demonstrate the method, and can now be replaced by catalyst nanoparticles (e.g., nickel, molybdenum sulfide, or cobalt-based) embedded in a semiconducting polymer to create membranes for photocatalytic water splitting.