Designing ultratough, malleable and foldable biocomposites for robust green electronic devices

Polymers from renewable resources play a key role in the paradigm shift towards a sustainable society. However, two common bioplastics, polylactic acid (PLA) and polyhydroxybutyrate (PHB) still lack the toughness and flexibility for practical applications. This work reports a design strategy to fabricate robust biocomposites based on PLA and PHB by direct mixing with a small amount of biodegradable poly(ethylene oxide) (PEO). The PLA/PHB/PEO green composites exhibit an extreme elongation of similar to 300% (50-fold increase) and a tensile fracture energy up to similar to 87 MJ m(-3) (90-fold increase), while maintaining high strength (similar to 49 MPa) and modulus (similar to 3.4 GPa) comparable to commercial poly(ethylene terephthalate). Even after repeated bending, folding and crumpling, the biocomposite film remains highly stretchable (elongation similar to 100%). The excellent mechanical performance is attributed to interfacial miscibility and entanglement networks driven by favorable mixing entropy. The reported composite is the first PLA/PHB based bioplastic that can be shaped, folded and crumpled, demonstrating its prospects as a substrate in green flexible electronic devices. This design strategy opens ample opportunities for facile preparation of biopolymer materials for future applications.