PFAS-Free Waterborne Amphiphobic Coatings with Excellent Substrate Independent Adhesion

The research on liquid-repellent surfaces and interfaces has made substantial progress over the past decade due to their universal importance in both fundamental science and practical applications, ranging from energy and healthcare to contamination prevention, anti-condensation, anti-icing, and anti-biofouling etc. However, the widespread adoption of such materials is constrained by two major challenges: (i) the use of fluorine-based compounds, specifically per- and polyfluoroalkyl substances (PFAS), which offer exceptionally low surface energy but are bio-persistent and environmentally hazardous, and (ii) poor adhesion to underlying substrates which makes them vulnerable to mechanical degradation. Due to global warming and the growing scarcity of resources, there is an urgent need to develop more robust and sustainable solutions. Engineering resilient surfaces with enhanced durability, utilizing environmentally benign chemicals, presents a viable approach to addressing these challenges. Such advancements can contribute to sustainable material design while minimizing environmental impact.
In this study, we propose a strategy to tackle these critical challenges by rationally selecting polyurethane for its exceptional substrate-independent adhesion, combined with metal-organic frameworks (MOFs) that offer precise nanotextures (nanohierarchy) and impeccable intercalation characteristics.
We present a water-based spray formulation of non-fluorinated amphiphobic (repellent to water and low surface tension liquids) coatings by combining commercial polyurethane and nanohierarchical MOF followed by post-functionalization with flexible alkyl silanes. The resulting surfaces are smooth, highly transparent, and demonstrate excellent amphiphobicity across a broad range of low surface tension liquids, including water, alcohols, and ketones. These coatings can withstand temperatures up to 200 °C, endure cyclic tape peeling, resist high-speed water jets (approximately 35 m/s), and exhibit low ice adhesion of ≤30 kPa, significantly below the threshold for anti-icing surfaces (<100 kPa). The multi-functionality, robustness and scalability (production and applicability, both), make this formulation a promising alternative to PFAS-based hazardous coatings.