Synthesis and Tunable Properties of Chemically Recyclable Multiblock Copolymers via Tandem Olefin Metathesis Polymerizations

Chemical recycling, in which materials are depolymerized to monomer, enables access to repeated, closed-loop recycling. However, current routes to chemically recyclable polymers typically rely on synthesizing monomers with cleavable heteroatomic linkages or tailored ring strains. In this work, we report the synthesis of all-hydrocarbon chemically recyclable multiblock copolymers containing (1,n′-divinyl)-oligocyclobutane (DVOCB(n)). DVOCB(n) is synthesized from the Fe-catalyzed reversible [2+2]-cycloaddition of butadiene, a commodity monomer, and is semicrystalline. Using commercially available all-hydrocarbon monomers, we developed a tandem ring-opening metathesis polymerization-acyclic diene metathesis approach which enabled the synthesis of materials with octylene soft segments and systematic variations in DVOCB(n) hard-segment length and content (10-50 wt % DVOCB(n)). We characterized the thermo-mechanical properties of the resulting multiblock copolymers using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and wide-angle X-ray scattering. By tuning the DVOCB segment length and content, DSC and DMA analysis revealed a broad spectrum of tunable melting temperatures (45-120 °C) and rubbery plateau moduli. Finally, ethenolysis of these copolymers was demonstrated and pristine DVOCB(n) recovered, thus offering potential end-of-life circularity for these materials.