Spontaneous polycatenation into linear polycatenanes

<jats:p>Mechanical bonds, which connect components through topological interlocking, are recognized alongside chemical bonds and non-covalent interactions as a fundamental mode of molecular connectivity1-3. Yet, unlike covalent and supramolecular polymerization, autonomous chain propagation through topological interlocking has remained unrealized4-8. Here we report a one-pot spontaneous polycatenation, in which cage-like monomers generated in situ from two complementary precursors undergo successive catenation to afford linear polycatenanes with a number-average degree of polymerization over 200. We show that successful polycatenation relies on two conditions: a monomer geometry that preserves two sites available for continued interlocking, thereby suppressing chain-terminating interwoven topologies; and persistent non-covalent interactions, realized here through π–π stacking between the two precursors, that provide sufficient enthalpic compensation to favour successive interlocking over entropically favoured random branching. These findings establish polycatenation as a polymerization mode driven by mechanical bonds, extending chain propagation beyond covalent and supramolecular paradigms.</jats:p>