Design of environmentally degradable polyethylene-like polyesters and eco-friendly recycling via commercial enzymes

Abstract

Polyethylene-like (PE-like) polyester represents a potential alternative to the most widely manufactured polyethylene materials, but has limited degradation rates and an environmentally unfriendly chemical recycling pathway. However, the green enzymatic recycling process giving back the monomer is often constrained by the crystalline structures and the limited hydrolytic activity of the enzyme. Here, the bio-based pyrrolidone diacid was selected for the core site for both accelerated hydrolysis and substrate–enzyme binding in the design of PBTDP copolyesters. The obtained PBTDP copolymers displayed high crystallinity and rapid crystallization, which were comparable to those of commercial HDPE. They exhibited remarkable toughness, with elongation exceeding 1000%. Additionally, they hydrolyzed in an aqueous environment at 37 °C and underwent rapid degradation catalyzed by commercial Candida antarctica lipase B enzyme within 10 days. The role of pyrrolidone units as hydrophilic sites and the hydrolytic mechanism were further elucidated through Fukui function analysis and DFT calculations. Furthermore, molecular dynamics (MD) simulations revealed that the pyrrolidone units engaged in non-covalent interactions for substrate–enzyme binding, increasing the population of the pre-reaction state conformations favorable for nucleophilic attack. Notably, the rapid enzymatic degradation of PBTDP20 resulted in the recovery of more than 92% of reusable 1,14-tetradecanedioic acid under mild conditions, further achieving the closed-loop recycling of copolyesters. Overall, the advantageous performance, environmental degradation, and practical enzymatic recyclability make PBTDP a promising candidate for sustainable PE-like materials.