Biodegradable Dual‐Network Cellulosic Composite Bioplastic Metafilm for Plastic Substitute

Abstract With the escalating environmental and health concerns over petroleum‐based plastics, sustainable and biodegradable cellulosic materials are a promising alternative to plastics, yet remain unsatisfied properties such as fragility, inflammability and water sensitivity for practical usage. Herein, we present a novel dual‐network design strategy to address these limitations and fabricate a high‐performance cellulosic composite bioplastic metafilm with the exceptional mechanical toughness (23.5 MJ m −3 ), flame retardance, and solvent resistance by in situ growth of cyclotriphosphazene‐bridged organosilica network within bacterial cellulose matrix. The phosphorus, nitrogen‐containing organosilica network, verified by the experimental and theoretical results, plays a triple action on significantly enhancing tensile strength, toughness, flame retardance and water resistance of composite bioplastic metafilm. Furthermore, cellulosic bioplastic composite metafilm demonstrates a higher maximum usage temperature (245 °C), lower thermal expansion coefficient (15.19 ppm °C −1 ), and better solvent resistance than traditional plastics, good biocompatibility and natural biodegradation. Moreover, the composite bioplastic metafilm have a good transparency of average 74 % and a high haze over 80 %, which can serve as an outstanding substrate substitute for commercial polyethylene terephthalate film to address the demand of flexible ITO films. This work paves a creative way to design and manufacture the competitive bioplastic composite to replace daily‐used plastics.