Structure-Property Relations in Chemically Recyclable Poly(oligocyclobutane) Polymers from Acyclic Diene Metathesis

Single-use plastics are ubiquitous in everyday life due to their low cost, durability, and convenience. However, when sorting, shredding, and melting plastics for reuse, property degradation arises due to chain scission or branching of the material. Materials capable of chemical reversibility back to the monomer form bypasses this limitation by theoretically allowing for closed-loop chemical recycling. Here, we investigate a new class of chemically recyclable polymers derived from butadiene, a commodity monomer. By chain-extending oligocyclobutane building blocks, polymers of tailored molecular weight and architecture are synthesized. Using a combination of thermomechanical analysis techniques, the thermo-oxidative stability, crystalline behavior, and mechanical properties of the polymers are investigated as a function of molecular weight and compared to those of traditional commodity polymers. Exposure of the chain-extended polymers to the metal catalyst used originally for their synthesis results in depolymerization back to the oligocyclobutane building blocks. Importantly, subsequent polymerization-depolymerization cycles result in no discernible change in polymer properties.