Trojan horse repeat units for chemically recyclable PET polyesters

Overview

This technology introduces specialized comonomers—called "Trojan Horse" repeat units—at loadings below 10 mol % into PET (polyethylene terephthalate) polyesters. These comonomers function as internal catalysts, enabling rapid depolymerization under mild hydrolysis, methanolysis, or glycolysis conditions. The resulting hybrid polyesters maintain PET-like mechanical and barrier properties while depolymerizing several times more readily than virgin PET, offering a practical pathway to closed-loop chemical recycling of PET packaging and films.

The approach addresses a critical limitation in PET recycling: conventional chemical recycling requires harsh conditions that are energy-intensive and economically challenging. By embedding catalytic functionality directly into the polymer backbone, this technology enables efficient monomer recovery using mild temperatures and benign reagents, making it compatible with existing recycling infrastructure.

Technical specifications

Key features:

• Comonomer loadings of 1–10 mol % preserve PET-like properties while enabling catalytic depolymerization
• Over 100 exemplary PET copolymers prepared with film- and bottle-grade intrinsic viscosities
• Achieves complete hydrolysis to monomer in pure water at 180 °C in several hours
• Supports alkaline hydrolysis at temperatures up to 100 °C
• Compatible with mild alkaline methanolysis at temperatures below 80 °C
• Retains or improves mechanical and barrier properties compared to virgin PET
• Builds on proof-of-concept work with 5 mol % dihydroxyterephthalate (DHTE) copolymers
• Validated across multiple "Trojan Horse" copolymer chemistries through a Department of Energy-funded project

How it works:

The "Trojan Horse" comonomers are integrated into the PET backbone during polymerization. When exposed to specific recycling conditions—water, mild alkali, or methanol—these repeat units catalyze the cleavage of ester bonds throughout the polymer chain, yielding recoverable monomers. This contrasts with conventional PET, which resists depolymerization under the same mild conditions.

Technology readiness level

The technology is currently at TRL 4–5, with lab-scale validation completed across more than 100 copolymer formulations. The next development phase involves down-selecting to a commercializable "Trojan Horse" molecule, optimizing its synthesis, scaling production to pilot/demonstration scale (100–500 kg), and producing approximately 1,000 kg of highly recyclable PET for a pilot demonstration in applications such as films or bottles. A contract manufacturer will be engaged for pilot-scale implementation.