Improved surface properties in spray-coated PU/TiO2/graphene hybrid nanocomposites through nonsolvent-induced phase separation

Herein, superhydrophobic and antibacterial polyurethane (PU) nanocomposite films loaded with titanium dioxide (TiO2) nanoparticles and graphene nanoplatelets were fabricated via a spray coating technique. The nonsolvent-induced phase separation (NIPS) process increased the films' roughness and hydrophobicity. In addition to the effective role of nonsolvent in phase separation, graphene also played the nucleating role and promoted the NIPS process. Based on scanning electron microscopy, atomic force microscopy, and optical microscopy results, it was found that the combinational use of TiO2, graphene, and nonsolvent leads to a hierarchical structure with a high extent of uniform surface roughness resulting in a superhydrophobic/roll-off behavior (water contact angle = 159°, sliding angle