New hydrophobic and transparent fluorine-free chitosan-based coatings

The results of the research published in Carbohydrate Polymers
crabs and hydrophobic and trasparent coatings

PFAS (Per- and Polyfluorinated Substances) are a class of molecules containing fluorine atoms that are widely used to produce water-repellent and non-stick surfaces, with applications ranging from textiles to construction. Their widespread use is rising concern regarding their possible toxicity combined with a very long-lasting lifetime, leading the European Union to ban the use of some molecules belonging to the category (PFOA and PFOS in 2020). In particular, the PFAS production industry has caused extensive damage to the local water supply in America and Europe, a problem which in Italy is especially felt in Veneto, in the province of Vicenza.

In this context, it is necessary to develop non-toxic and biodegradable alternatives to replace PFAS. The researchers of the Surface Engineering and Fluid Interfaces laboratory (SEFI Lab) at the Department of Materials Science of the University of Milano-Bicocca, with the research led by Dr. Irene Tagliaro and Prof. Carlo Antonini and in collaboration with the Dr. Sabrina Bertini of the Ronzoni Institute of Chemistry and Biochemistry, demonstrated the possibility of using modified biopolymers to create hydrophobic, non-toxic and sustainable coatings.

In the study “Chitosan-based coatings with tunable transparency and superhydrophobicity: a solvent-free and fluorine-free approach by stearoyl derivatization” (DOI: 10.1016/j.carbpol.2022.120424) recently published in the prestigious scientific journal Carbohydrate Polymers (Impact Factor 10.723, Journal Citation Report (Clarivate Analytics, 2021)), the selected biopolymer was chitosan, a polysaccharide derived from chitin: the latter is a crustacean exoskeleton constituent, which represents the second most abundant polysaccharide in nature, after cellulose. Chitosan is a low-cost material, as it is a waste product of the crustacean food industry, which has developed rapidly in recent years, especially in Asia, counting a global production of tens of million tons per year.

The scientific study by Dr. Tagliaro and colleagues proposes a method for producing chitosan-based coatings, with the possibility of tuning its transparency and superhydrophobicity properties. This result was obtained by a chemical modification of the biopolymer structure, combined with the creation of a solvent-free deposition method. The developments of this work include an in-depth study on the durability of the coatings for a possible industrial application, together with the study of the environmental impact of the process.

Cover art by Heloise Chochois