Multi-scale Block Copolymer Coating That Induces Hydrophobic Properties on Inorganic Surfaces

Superhydrophobic surfaces hold promise of a technology with various applications spanning different environments, service conditions and length scales. We demonstrated a cost-effective and robust method for imparting superhydrophobicity to target surfaces through self-assembly of block copolymers (BCPs), while the optical properties of underlying materials are preserved. Our approach involves iterative steps of spin-coating, annealing, and etching of different molecular weight (MW) PS-b-PDMS BCPs into multi-layer hierarchal structure. The resulting periodic pattern introduces necessary nanoscale roughness to trap air and increases hydrophobicity of surfaces, and can be controlled by altering tuning parameters such as MW and composition of BCPs. To understand how superhydrophobicity emerged from multi-layer hierarchal BCP structures, multilayer BCP models were constructed by matching experimental observed dimensions, sweeping through wetting configurations, and calculating externally observed contact angles. The results verified the observed experimental trend, demonstrating superhydrophobicity behavior through modulation of roughness at different layers and formation of air pockets. This technology fulfills a pressing need for superhydrophobicity in optically sensitive settings.