Performance-Advantaged Stereoregular Recyclable Plastics Enabled by Aluminum-Catalytic Ring-Opening Polymerization of Dithiolactone

Chemically recyclable polymers that can depolymerize into their constituent monomers are attractive candidates to replace non-recyclable petroleum-derived plastics. However, the physical properties and mechanical strengths of depolymerizable polymers are commonly insufficient for practical applications. Here we demonstrate that by proper ligand design and modification, aluminum complexes can catalyse stereoretentive ring-opening polymerization of dithiolactone, yielding highly isotactic polythioesters with molar masses up to 45.5 kDa. This material can form crystalline stereocomplex with a T-m of 94.5 degrees C, and exhibits mechanical performances comparable to petroleum-based low density polyethylene. Exposure of the polythioester to aluminum precatalyst used to synthesized it resulted in depolymerization to pristine chiral dithiolactone. Experimental and computational studies suggest that aluminum complexes have appropriate binding affinity with sulfide propagating species, thereby avoiding catalyst poisoning and minimizing epimerization reactions, which has not been accessible using other metal catalysts. Overall, aluminum catalysis provides access to performance-advantaged stereoregular recyclable plastics as a promising alternative to petrochemical plastics, thus incentivizing improved plastic sustainability.

Automated summary

By designing proper ligands and modifying aluminum complexes, stereoretentive ring-opening polymerization of dithiolactone can be catalyzed, resulting in highly isotactic polythioesters. The resulting material exhibits mechanical performance comparable to petroleum-based low density polyethylene and can form crystalline stereocomplex. Aluminum catalysis provides access to performance-advantaged, recyclable plastics as a promising alternative to petrochemical plastics, contributing to improved plastic sustainability.