Aliphatic–Aromatic Copolyesters with Waste-SourceableMultiple Chain-Length Building Blocks

Sourcing commodity polymers from sustainable alternative feedstocks, such as those derived from plastic waste or biobased resources, is a promising approach to alleviate the reliance on finite fossil fuel stocks for the production of virgin plastics. Linear aliphatic dicarboxylic acids of multiple chain lengths can be obtained from polyethylene (PE) waste, and their use in the synthesis of aliphatic polyesters has recently been demonstrated. To improve the materials’ properties of polyesters derived from multiple chain-length dicarboxylates, we herein combined this feedstock with terephthalate as an aromatic monomer unit to yield aliphatic–aromatic copolyesters. We established structure–property relationships for copolyesters derived from aliphatic dicarboxylates of multiple chain lengths (C₄–C₂₀) as a model for catalytic oxidation products of PE waste, or from 1,18-octadecanedioate as reference materials for polyesters from single, long chain length dicarboxylates. Thermal properties and solid-state structures were dominated by the ratio of aliphatic to aromatic monomer units rather than the identity of the aliphatic dicarboxylate or diol components. We demonstrated upscaling of the copolyester synthesis, as well as processability and mechanical properties of a multiple chain length copolyester, which showed comparable properties to the commercial polybutylene adipate-<i>co</i>-terephthalate. Finally, we showed an alternative production via catalytic transesterification and thus postmodification of premade polyesters, including postconsumer polyethylene terephthalate, as model waste sources.