Novel Fluoropolymer Blends for the Fabrication of Sprayable Multifunctional Superhydrophobic Nanostructured Composites

We report a highly efficient technique to form novel fluoropolymer blend dispersions containing poly(vinylidene fluoride) (PVDF) and a fluorinated acrylic copolymer using a cosolvent system- comprising N-methyl-2-pyrrolidone (NMP), acetone, and water under pH control. We also show that certain surface-functionalized, high-aspect-ratio nanostructured materials, such as organoclay and carbon nanowhiskers (CNWs), can be easily dispersed in these fluoropolymer blends to fabricate durable and functional superhydrophobic composite coatings upon spray casting. Both clay and CNW superhydrophobic coatings also repel lower surface tension liquids, such as water alcohol mixtures (similar to 40 mN/m). Repellency is characterized using droplet sessile contact angle and contact angle hysteresis. Both clay and CNW-based composite coatings display self-cleaning properties (low contact angle hysteresis) for both water and water alcohol mixtures. Additionally, electrical conductivity measurement of CNW composite coatings demonstrates the ability to fabricate multifunctional superhydrophobic composites using these fluoropolyrner dispersions. The nanoparticle concentration required in these composite coatings for water and water alcohol repellency is compared with a previously reported PVDF-based coating system. Wettability is interpreted within the framework of the Wenzel and Cassie-Baxter wetting theories.