Reprocessable and Recyclable Cellulosic Network Polymers with Intrinsic Flame Retardancy via Dynamic Covalent Cross-Linking

Developing sustainable, high-performance biobased materials is critical for reducing dependence on petroleum-derived plastics. Cellulose is the most abundant and renewable polymer resource, yet current cellulose-based materials often suffer from limitations such as flammability, water sensitivity, limited processability, and recyclability in practical use. Herein, we propose an integrated strategy to reconfigure cellulose's hydrogen-bonded network into a dynamic covalent architecture while incorporating flame-retardant units in situ. The resulting thermo-processable cellulosic network polymers (CAA-DDPNs) exhibit high tensile strength (46-65 MPa), self-extinguishing behavior, and resistance to both water and common organic solvents. Compared with several engineering plastics, CAA-DDPN films demonstrate higher thermal stability (onset 281-301 °C) and an ultralow coefficient of thermal expansion (0.9-1.8 ppm K^-1). More importantly, the dynamic linkers enable efficient chemical depolymerization to recover monomers, thereby overcoming the limited chemical recyclability of prior cellulose materials. The combination of mechanical robustness, thermal and chemical resilience, flame retardancy, and circularity makes CAA-DDPNs a viable, eco-friendly alternative to conventional petroleum-based plastics.