Chemically Recyclable Butadiene-Derived Poly(oligocyclobutane)s from Acyclic Diene Metathesis

Commodity polyolefins account for the majority of plastic waste but present thermodynamic challenges for depolymerization and upcycling due to their high thermal and chemical stability. Here, the synthesis and characterization of a chemically recyclable polyolefin is reported that is derived in two steps from butadiene, a feedstock olefin. Acyclic diene metathesis (ADMET) polymerization of (1,n′-divinyl)oligocyclobutane (DVOCB), a telechelic oligomer formed by the reversible [2+2] cycloaddition-oligomerization of butadiene, yielded pDVOCB, a new polyolefin architecture. Characterization of pDVOCB by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS), dynamic mechanical analysis (DMA), and tensile testing established high crystallinity, high thermal stability, and comparable thermal properties and mechanical behavior to those of commodity polyolefins. The length of the DVOCB monomer was used to tune the thermomechanical properties of the resulting polymer. Exposure of pDVOCB to excess ethylene under ADMET conditions resulted in >99% depolymerization back to DVOCB with minimal purification required. Selective depolymerization and recovery of DVOCB was also demonstrated from a mixed polymer waste stream, as well as complete depolymerization back to pristine butadiene.