PFAS-free biopolymer-based coatings with tailored wettability

Polysaccharides are emerging as a versatile platform for the design of sustainable functional coatings. Their polymeric backbone rich in hydroxyl, carboxyl or amino groups provides a high density of chemically addressable sites that enable functionalization and fine tuning of surface properties. Also, their intrinsic ability to form films or micro- and nano-structures makes them particularly attractive for controlling interfacial phenomena. Through suitable chemical modification, polysaccharides can therefore provide a modular strategy to tailor wettability across a wide range of regimes, from highly hydrophobic to strongly hydrophilic surfaces. In this context, polysaccharides represent an attractive alternative platform in the ongoing phase-out of per- and polyfluoroalkyl substances (PFAS), standing out as versatile and sustainable materials thanks to their natural abundance, biodegradability and non-toxicity. Here we present PFAS-free polysaccharide-based coatings ranging from superhydrophobic to superhydrophilic. Superhydrophobic coatings were obtained by modifying chitosan with stearoyl groups through esterification and amidation reactions with stearoyl chloride, followed by purification and freeze-drying to obtain a fine powder. The coating was applied to cellulose acetate and polyester substrates using a solvent-free deposition method, yielding high water contact angles due to the combined effect of hydrophobic aliphatic chains and micro-/nano-scale surface roughness, as confirmed by SEM analysis. The durability of the coatings was assessed under acidic aqueous conditions, UV exposure, and mechanical stress. Additional analyses, including TGA-FTIR and biodegradability tests, highlight the environmentally compatible nature of the modified chitosan (Tagliaro et al., 2023, 2024). Superhydrophilic and hydrophilic polysaccharide coatings were developed to achieve icephobic properties (Marelli et al., 2025). Chitosan and hyaluronic acid were deposited as thin coatings on glass substrates by anchoring them with commercial adhesion promoters. The combination of smoothness and hydrophilicity resulted in lowering ice adhesion in regimes of ice sliding never reported before, especially in the case of hyaluronic acid. These results demonstrate the potential of polysaccharide-based coatings as sustainable PFAS-free platforms for controlling surface wettability in advanced applications.