A closed loop cycle for polymer production and disposal is needed to handle the estimated half a billion metric tons a year of polymer that will be used by 2050. Current methods for polymer recycling are insufficient to meet this need. We have demonstrated that the ring-opening copolymerization of an unstrained monomer, γ-butyrolactone, and a strained monomer, ε-caprolactone, produces a chemically recyclable polymer that proceeds with good mass recovery of strained and unstrained monomers. The copolymerization is an enthalpy controlled process driven by the ring-opening of the strained ε-caprolactone monomer. The depolymerization is an entropy controlled process that is driven by the cyclization of the unstrained γ-butyrolactone monomer. Depolymerization of the resulting copolymer yielded greater than 80% and 75% mass recovery of the unstrained and strained monomer, respectively. The recovered monomers can be used without further purification to reproduce the original copolymer, closing the loop for polymer recycling. This proof-of-principle demonstration further diversifies the types of polymers that can be chemically recycled, and provides a strategy that enables tuning of polymer mechanical properties and polymer degradation rates by utilizing two separate monomers to modulate each property independently.

Accessing chemically recyclable polymers through ring-opening copolymerization/depolymerization of strained monomers with unstrained monomers

ACS Spring Meeting 2021

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