Cold Alkali Treatment Enabled Stretchable yet Mechanically Strong All-Cellulose Composite

Biodegradable cellulose films are promising alternatives to plastics, but achieving stretchable all-cellulose composites (ACCs) remains challenging. Here, we present a scalable strategy for creating stretchable yet mechanically strong ACCs. This approach integrates swollen-regenerated microfibers with dissolution-regenerated cellulose to form multiscale architectures, achieved through mechanical pretreatments and cold NaOH treatment of kraft pulp, followed by vacuum filtration and press-drying. Swollen-regenerated microfibers establish preferential sacrificial networks that enhance mechanical strength through nanofiber pull-out, while dissolution-regenerated cellulose matrix facilitates nanoscale load transfer, maintaining ductility. The ACC achieves a tensile strength of 89.0 MPa, a strain to failure of 24.7%, and a work of fracture of 17.3 MJ m^-3─1.3 times stronger, 1.5 times more stretchable, and 3.8 times tougher than microfibrillated cellulose films. With added benefits of wet strength, grease resistance, oxygen barrier property, and biodegradability, this work demonstrates a scalable approach to engineering multiscale cellulose networks for sustainable packaging.