Thermally Stable and Chemically Recyclable Poly(ketal-ester)s Regulated by Floor Temperature

Area of Science:

• Polymer Chemistry
• Materials Science
• Sustainable Chemistry

Background:

• Chemical recycling to monomers (CRM) is key for a circular plastic economy, often focusing on ceiling temperature (Tc) modulation.
• Polymers with low Tc, like poly(γ-butyrolactone) (PGBL), have limited thermal stability (decomposition ~200 °C).
• Floor temperature (Tf)-regulated polymers, especially from macrolactone ring-opening polymerization (ROP), offer enhanced thermodynamic stability but are underexplored.

Purpose of the Study:

• To develop a novel Tf-regulated, closed-loop chemically recyclable polymer using a biobased monomer.
• To investigate the thermal stability and recyclability of the synthesized poly(ketal-ester) (PHOD).
• To explore copolymerization for tunable properties and recyclability.

Main Methods:

• Design and synthesis of a biobased macrocyclic diester monomer (HOD).
• Entropy-driven ring-opening polymerization (ROP) of HOD to produce poly(ketal-ester) (PHOD).
• Assessment of thermal stability (Td,5%) and closed-loop chemical recyclability at room temperature using 1-butyllium potassium (tBuOK).
• Copolymerization of HOD with pentadecanolide (PDL).

Main Results:

• High-molar mass PHOD was synthesized with exceptional thermal stability (Td,5% up to 353 °C), maintaining 345 °C even without catalyst removal.
• PHOD demonstrated rapid (1 min) closed-loop chemical recyclability at room temperature.
• Copolymers (PHOD-co-PPDL) exhibited tunable mechanical properties and recyclability of both monomer units.

Conclusions:

• Tf-regulated PHOD offers a promising alternative to Tc-regulated polymers, overcoming thermal stability limitations.
• The developed material enables efficient, low-temperature chemical recycling, supporting a circular plastic economy.
• Copolymerization provides a route to advanced materials with tailored performance and recyclability.