Fabrication of superhydrophobic and heat-insulating antimony doped tin oxide/polyurethane films by cast replica micromolding.

A novel process for fabricating superhydrophobic and heat-insulating polymeric nanocomposite films was developed. Briefly, antimony doped tin oxide (ATO) nanoparticles that commonly endow coats heat-insulating and transparent functions were mixed into commercial waterborne polyurethane (WPU) suspensions to obtain ATO/WPU suspensions, which were then cast onto poly(dimethylsiloxane) (PDMS) stamps replicated from fresh lotus leaves. After being dried and peeled off from stamps, ATO/PU films with superhydrophobic surface and heat-insulating property were created, while PU films without ATO only showed high hydrophobicity. Scanning electron microscopy (SEM) imaging showed the surface of ATO/PU superhydrophobic films had unique micro- and nano-structures similar with those on the lotus leaf. On the contrary, no obvious nano-structures were found on the surface of pure PU films, demonstrating mixing functional nanoparticles into polymers is a necessary and feasible step in creating superhydrophobic and functional films by replica molding method.