Depolymerization of robust polyetheretherketone to regenerate monomer units using sulfur reagents

Area of Science:

• Polymer Chemistry
• Materials Science
• Sustainable Chemistry

Background:

• Super engineering plastics, including polyetheretherketone (PEEK) and polyphenylene sulfide, offer high thermal stability and mechanical strength.
• Their inherent robustness, however, poses significant challenges for depolymerization and chemical recycling into monomers or low-weight molecules.
• Current chemical recycling methods for these advanced polymers remain largely underdeveloped.

Purpose of the Study:

• To develop an effective chemical recycling method for insoluble polyetheretherketone (PEEK).
• To demonstrate the depolymerization of PEEK into useful chemical intermediates.
• To explore the potential for creating new polymers from the recycled products.

Main Methods:

• Depolymerization of polyetheretherketone (PEEK) using sulfur nucleophiles targeting carbon-oxygen bond cleavage.
• Formation of benzophenone dithiolate and hydroquinone as primary depolymerization products.
• Conversion of benzophenone dithiolate with organic halides to yield dithiofunctionalized benzophenones.

Main Results:

• The depolymerization method successfully broke down insoluble PEEK via a solid-liquid reaction, irrespective of its physical form (pellets, films).
• The method proved effective for both neat and fiber-reinforced PEEK (carbon- or glass fiber-enforced).
• Dithiofunctionalized benzophenones were synthesized and subsequently converted to diiodobenzophenone, suitable for polymerization.

Conclusions:

• A novel and efficient chemical recycling pathway for polyetheretherketone (PEEK) has been established.
• This method facilitates the recovery of valuable monomers from robust engineering plastics.
• The derived diiodobenzophenone can be utilized for synthesizing new polymers, promoting a circular economy for high-performance materials.