Cyclobutane‐Programmed Sustainable Materials With Service‐Induced Self‐Reinforcement, Optical Security, and Closed‐Loop Chemical Recycling

High durability and fully recyclable materials represent a promising sustainable development strategy to address the escalating global plastic crisis, but there is always a trade-off between aging resistance and easy chemical recycling. We present an unprecedented biomass-derived polyester molecularly designed strategy that uniquely integrates service-triggered antiaging self-reinforcement with easy monomer-level closed-loop recyclability programmed with a cyclobutane mechanophore unit. During service, polyester undergoes a [2+2] cycloaddition that forms covalent cyclobutane cross-links, creating an in situ self-reinforcing network. This transformation increases oxygen-barrier performance by up to 330% and improves tensile strength by 21%, enabling performance amplification rather than degradation. The same cyclobutane units are engineered to undergo mechanochemical cycloreversion, providing a force-activated de-cross-linking pathway that allows complete monomer-level depolymerization under mild conditions. The repolymerized materials are indistinguishable from the original. Additional features, including ultraviolet shielding and fluorescence-based anti-counterfeiting, highlight its multifunctionality. This biomass material demonstrates a unified molecular strategy that enables self-reinforcement and efficient, easy recycling, offering a viable pathway for next-generation sustainable polymers.