Disequilibrating Dynamic Polymers for Spontaneous Recyclability

Chemical recycling of synthetic polymers is key to our future circular plastics economy1–3. Current chemical solutions rely on either catalyst design or introducing weak bonds.4–6 The former approach doesn’t tackle the thermodynamic trap of conventional plastics, while the latter usually compromises materials performances. Despite recent advances in ring-strain engineering of lactone-based polymers allowing catalyst-enabled recyclability,1,6,7 polymer-to-monomer recycling processes under mild, waste-free, and cost-affordable conditions remain a formidable challenge. Here, we report an intrinsically recyclable polymer disequilibrated by kinetic control of bulk reconstruction mediated with dynamic bonds, enabling spontaneous polymer-to-monomer conversion by direct solid-to-solid (crystal) transition. The key feature of the system is to couple two types of dynamic chemical equilibria, i.e., noncovalent self-assembly of side-chains and dynamic covalent polymerization of mainchains. We discovered that controlling the sidechain H-bond stacking geometry could be used to spatially separate the polymerizing moieties of monomers in the solid state and bias the monomer/polymer equilibrium toward the direction of depolymerization. As a result, a semi-crystalline, Nylon-like, and easy-to-prepare polymeric material can be spontaneously recycled into crystalline monomers using a mild thermal activation process (120°C), featuring quantitative recycling yield, high monomer purity (over 90%) at low-cost while avoiding the use of any solvent or catalyst during recycling. Life-cycle assessment shows a remarkably advantageous environmental footprint of this technology compared with solvent-based chemical recycling routes. These findings offer a supramolecular solution towards cost-effective closed-loop recycling of covalent polymers.