Cycloreversion-enhanced toughness and degradability in mechanophore-embedded end-linked polymer networks.

Enhancing the toughness while achieving triggerable degradation in single-network polymer systems without modifying their inherent chemical composition or network architecture remains a significant challenge. Here we demonstrate a smart end-linked polymer network that "self-strengthen" during use yet "self-destruct" upon certain stimuli. Embedding nonscissile cyclobutane-fused tetrahydrofuran mechanophores within the middle of end-linked polymer networks significantly enhances both toughness and degradability. Under mechanical stress, the force-coupled cycloreversion of these mechanophores releases concealed chain segments, enabling single-network materials to exhibit threefold toughness and tenfold tear energies compared to conventional counterparts. Additionally, ball-milling griding of the bulk material unveils acid-sensitive enol ether units, leading to a markedly improved degradation profile under acidic conditions. This dual effect-originating from the force-coupled cycloreversion of cyclobutane-fused tetrahydrofuran mechanophores-provides an ideal combination of superior mechanical performance and on-demand degradability.