“Hetero-Furan Unit” Drives a Spontaneous Leaf-Vein Bioinspired Multiscale Design for Ultra-Robust, Lightweight, and Recyclable Polymers

Inspired by the interpenetrating network of nature leaf-vein, non-composite polymer materials with ultra-robust, lightweight, and fully recyclable properties are synthesized by a "hetero-furan unit"-driven multiscale design. That is, starting from the primary chemical structure at the molecular scale, the furan group is copolymerized in a polymer chain (polyethylene terephthalate, PET). Then, these "hetero-furan units" simultaneously regulate the secondary chain conformation (nano-scale) and the tertiary aggregate structure (micro-scale) of the PET copolymer, thereby driving the spontaneous growth of the "leaf-vein"-mimicking crystal reinforcement phase. Requiring only less than 1% furan units, corresponding copolymer PET-FN1 not only exhibits surprising fourfold increase in toughness (tensile toughness of 346 MJ m–3 and impact strength of 69.8 kJ m–2) and 40% increase in tensile strength (83.6 MPa) but also achieves lower density and easy processing. This demonstrates the super-efficiency of this bioinspired multiscale design regulated by the original chemical structure. Especially, copolymer PET-FN1 can be quickly chemically recovered under mild conditions (80 °C, 4 h) to obtain raw monomers with a purity of 99.8%. This work opens up a new perspective for developing advanced polymer materials with excellent mechanical properties, lightweight, and environmentally friendly recycling, which will greatly benefit the global circular economy and sustainable development.