High Molecular Weight Biobased Long-Chain Aliphatic Polyesters with Degradability: Insights into Mimicking Polyethylene

Synthesis of high molecular weight long-chain aliphatic polyesters with mechanical properties similar to polyethylene is challenging. This study presents high molecular weight biobased polyesters synthesized via a three-step process involving transesterification, polycondensation, and postcondensation, using biobased 1,18-dimethyl octadecanedioate (C18-diester) and natural diols ranging from C3 to C12. All polyesters achieved weight-average molecular weights over 110 000 g/mol. The crystalline structures and thermomechanical properties of polyesters were largely influenced by the chain length of diols, with an odd–even effect observed. These polyesters exhibit tensile properties mimicking HDPE and LDPE, which allowed successful processing into filaments and 3D-printed objects. Although these polyesters exhibit semicrystalline structures similar to polyethylene, their melting temperatures are significantly lower, especially compared to HDPE. Chemical recycling of a representative polyester demonstrated its ability to undergo depolymerization and repolymerization, with the recovered polyesters displaying comparable mechanical properties to the virgin one. Coarse-grained molecular dynamic simulations of these polyesters demonstrated crystallization of the materials upon cooling from melts and reproduced the decrease in crystallization temperature with an increase in the ester-to-methylene ratio observed in the experiments. The proposed modeling approach allowed us to track the growth of crystalline domains upon cooling from the melt by characterizing the local nematic order parameter to quantify the effect of ester groups on the crystallization process. This study addresses common challenges that complicate synthesis and polymer processing, providing useful guidance for achieving reproducible polyester preparation.