Supramolecular chemical recycling of dynamic polymers

Current chemical approaches for recycling synthetic plastics rely on either catalytic reactions to break covalent bonds or introducing weaker bonds in the plastic structure. In the former approach, depolymerization remains an energetically demanding step due to the thermodynamic stability of the plastic, whereas in the latter approach, the recyclability of plastic usually compromises mechanical properties. Here we present a supramolecular chemistry principle that results in a catalyst-free and solvent-free polymer-to-monomer transformation of a series of kinetically stable poly(disulfide)s. The coupling of two dynamic chemical equilibria-H-bond self-assembed stacking of the sidechains and dynamic covalent polymerization of the backbone-reversibly regulates the monomer-polymer equilibrium through simple solvation/desolvation cycles. Following this principle, we synthesize thermodynamically metastable, yet kinetically stable, poly(disulfide)s with high crystallinity and tunable mechanical properties. Upon mild thermal activation at 120 °C, the plastic can be readily recycled into crystalline monomers with quantitative yields and monomer purity >90%. The monomers can then be used to regenerate origin-quality polymers. Our findings offer a supramolecular route for designing closed-loop recyclable synthetic polymers.