Mechanically Adaptive, Moisture-Tunable Cellulosic Nanocomposite Fibers and Films

Abstract Mechanically adaptive materials inspired by sea cucumber dermis exhibit reversible, water-tunable mechanical properties, yet their use in sustainable fibers remains unexplored. Here, humidity-responsive nanocomposite fibers based on hydroxypropyl cellulose and cellulose nanocrystals were produced by wet spinning into a CaCl2 coagulation bath. The fibers exhibit moisture-induced disintegration, dense packing and moderate CNC alignment, thereby enabling a percolating network. The Young’s modulus increases from 1.3 GPa for neat HPC to 3.6 GPa for nanocomposites containing 60 wt % CNCs, while the strength and strain at break decrease from 36 to 20 MPa and 3.5 to 0.7%, respectively. Under humid conditions, their Young’s modulus and tensile strength decreased to 18 MPa and 0.4 MPa, while their extensibility increased to 36%. Upon drying, the original mechanical properties of fibers and CaCl2-free films are fully restored. The combination of high stiffness and humidity-induced responsiveness expands the potential of mechanically adaptive nanocomposites for water-dispersible products.