Waterborne Polyurethane Nanocomposite with Chitin–Glucan Nanocrystals: A Tough, Stretchable, and Antifouling Polymer for Advanced Applications

Highly stiff, tough, and stretchable polycarbonate-polyurethane (PC-PUR) nanocomposites have been synthesized, exhibiting elongation of up to 1180% and notable antifouling properties. The materials are remarkably strongly reinforced by chitin–glucan nanocrystals (ChGNCs) obtained from fungal biomass, achieving nearly a 10-fold increase in modulus with only 1 wt % ChGNC. This effect arises from the nanoscale dimensions of the fibrous filler, its significant intercalation by the PC-PUR matrix, as well as from efficient hydrogen bonding of ChGNC amide groups to the chemically similar urethane or urea units in the hard segments of the matrix, or to the carbonate units in the soft ones. The H-bonding was studied in detail and proven by advanced NMR spectroscopy including two-dimensional dipolar resonance analysis. Synthesis of the nanocomposites employed waterborne polyurethane dispersions (WPUDs) as matrix precursors, offering multiple advantages such as enhanced safety, reduced health and pollution risks due to the elimination of volatile organic compounds (VOCs), ease of handling, and compatibility with aqueous additives, including hydrophilic suspensions of the ChGNC filler. This filler was obtained from commercial mycelium (Aspergillus niger) via a biocompatible defibrillation process, using a natural-compound-based deep-eutectic solvent (DES) mixture. Biological assays demonstrated the nanocomposites’ antifouling efficacy against Staphylococcus aureus and Escherichia coli. Our products hold application potential as advanced materials for high-performance coatings, as stiff and tough structural elastomers with antifouling properties, and after further optimization of the WPUD synthesis as biocompatible systems.