Glass-like transparent and heat-sealable films of cellulose nanoworms <i>via</i> ethanol triggered swelling of esterified cellulose

This study introduced a new and unique design of cellulose nanomaterials called cellulose nanoworms, which exhibit alluring properties for creating sustainable and advanced film structures. These nanoworms, which are being reported for the first time to the best of our knowledge, were obtained from wood-based cellulose pulp using an ethanol-induced swelling method of cellulose fibers, which were esterified with 2-octenylsuccinic anhydride in a deep eutectic solvent comprising imidazole and triethylmethylammonium chloride. When the hydrophilized fibers were exposed to ethanol, an intense ballooning phenomenon occurred, leading to the disintegration of the swollen fibers into an entangled network of cellulose nanoworms through ultrasonication. The cellulose nanoworms were further used as building blocks for the formation of films with advanced optical, surface, and thermal properties, as well as heat-sealable wrapping with desirable barrier and water resistance performance. Through the densely packed arrangement of nanoworms, the films exhibited high transparency of 92-93% without haziness or light scattering, water vapor permeability of 2.34 g μm m ⁻² d ⁻¹ kPa ⁻¹, ultra-low root-mean-square roughness (Rq) of 2.5 nm, and good liquid water resistance, as indicated by their high mechanical strength in wet states (13.1 MPa). Thus, cellulose nanoworms served as multifunctional biomaterials with advanced and tailorable properties, making them suitable for sustainable packaging, and electronic and optic applications.