The Fabrication of Fluorine‐Free Stretchable Superhydrophobic Films Using Inverse Vulcanization Sulfur Polymer

Stretchable superhydrophobic materials have gained attention in recent years though challenges remain for widespread use, including the need for rapid, energy-efficient, high-throughput, and fluorine-free fabrication methods. In this study, a stretchable superhydrophobic material is developed by coating parafilm with inverse vulcanization sulfur polymers. Silica (SiO2) nanoparticles are incorporated to create a Cassie–Baxter wetting state, achieving superhydrophobicity. The sulfur polymers are synthesized using perillyl alcohol (PER) at varying sulfur-to-PER ratios. The optimal coating formulation is determined to be 70 mg mL−1 of polymer, 50 mg mL−1 of SiO2 nanoparticles, and a sulfur-to-PER ratio of 1:1 (50% sulfur and 50% PER). The films maintained functionality when stretched due to controlled fragmentation that preserved the Cassie–Baxter wetting state. Mathematical modeling revealed a scaling relation between fragment area and thickness, showing that thicker layers produced larger fragments, impairing superhydrophobicity. This study also showcase the successful use of more sustainable bio-based solvents (2-methyltetrahydrofuran), where previous reports of similar processes have used chloroform. The fabricated films also demonstrated improved ultraviolet (UV-C) stability (150 min) compared to other sulfur polymer coatings reported in the literature. This coating of flexible substrates presents a simple and environmentally friendly method for producing stretchable superhydrophobic films.