Nonderivatized Regenerated Cellulose Film with Plastic-Like Elongation from TMAH·5H2O/Urea

Toxic petroleum-based plastics and the limited flexibility of conventional cellulose films have driven the need for sustainable, high-performance alternatives. We developed a nonderivatized regenerated cellulose film with high elongation using a biodegradable deep eutectic solvent (DES, TMAH·5H2O/Urea), which efficiently dissolves cellulose under mild, eco-friendly conditions. The resulting film exhibits mechanical properties comparable to PETG (57 MPa tensile strength, 47.33% elongation at break) and demonstrates high thermal stability (314 °C). Structural analysis via X-ray diffraction reveals that the cellulose crystal structure transitions from type I to type II and undergoes partial amorphization, reducing overall crystallinity from 60.9% in the raw material to 26.2% in the RC film formed via an ethanol solidification bath. FTIR analysis indicates that PETG-like elongation disrupts intramolecular hydrogen bonds and the crystalline network, and molecular dynamics simulations identify enhanced chain mobility as a key factor. These results present a green, scalable, biobased solution for replacing petroleum-based plastics. Combined flexibility, biocompatibility, and tunable properties of the film suggest promising applications in flexible packaging, biomedical membranes, and wearable electronics. Moreover, recyclable DES processing and inherent film biodegradability advance sustainable materials development.