Two-second surface-confined reconstruction of cellulose paper via a recyclable molten salt hydrate for water-resistant bioplastics

Abstract

The escalating plastic pollution crisis necessitates the development of sustainable bio-based materials with performance comparable to that of conventional plastics. Renewable and biodegradable cellulosic paper is an attractive alternative, yet its intrinsically poor water resistance and insufficient mechanical robustness limit its practical use. Conventional reinforcement strategies often rely on chemical modifiers, polymer coatings, or energy-intensive nanocellulose processing, increasing material complexity and environmental burden. Here, we report a 2-second surface-confined reconstruction strategy for cellulose paper using a recyclable molten salt hydrate (LiBr·3H₂O) system. The treatment induces localized partial dissolution at the fibre surface without crystalline transformation or chemical derivatization, generating an interpenetrating nanofibril–microfibre network while preserving the bulk fibrous skeleton. The resulting cellulose-based bioplastic exhibits a dry tensile strength of 69.9 MPa and a wet tensile strength of 27.1 MPa, corresponding to 3.3-fold and 22.2-fold improvements compared to untreated cellulosic paper, respectively. The additive-free process avoids organic solvents and crosslinking agents while enabling solvent recovery, consistent with key principles of green chemistry. The demonstration of durable cellulose-based straws further confirms material performance under realistic service conditions. Life cycle assessment further demonstrates a reduced global warming potential compared with polyethylene and polylactic acid counterparts. This work establishes a solvent-efficient and scalable pathway for upgrading conventional cellulose materials into high-performance biodegradable plastic alternatives.