Chemically Robust Superhydrophobic Poly(vinylidene fluoride) Films with Grafting Crosslinkable Fluorinated Silane

Abstract

A superhydrophobic surface with excellent chemical stability was fabricated using the spraying method, one of the most efficient technologies for producing large-area coatings at low cost. Poly(vinylidene fluoride) (PVDF) was used as a hydrophobic polymer material, and heptadecafluoro-1,1,2,2,-tetra-hydrodecyl)trichlorosilane (FTS), which reacts with moisture during curing, was used to improve the water repellency and durability. Spray coating of PVDF alone yielded PVDF nanostructures described by the Cassie-Baxter model. The water contact angle of a water droplet on this surface, however, was 128°, indicating that the surface was not superhydrophobic. On the other hand, spray-coating a mixed PVDF-FTS solution provided a complex and homogeneous nanostructured surface with excellent water repellency and a contact angle of up to 159°. Immersion of the PVDF-only film for 20 min in N,N-dimethylformamide (DMF), a good solvent for PVDF, led to complete dissolution of the film. By contrast, the PVDF-FTS film maintained its superhydrophobicity with a water contact angle of 151° after 20 min of immersion in DMF, and still exhibited a high contact angle of 142° after 1 h. The PVDF-FTS film developed in the present work should enable the production of large-area superhydrophobic coatings at low cost using a simple spray process. Moreover, the PVDF-FTS film displayed excellent stability against solvents, thus increasing its suitability for robust superhydrophobic applications.